processing and properties of nonferrous metals -...

VŠB-Technical University Faculty of Metallurgy and Materials Engineering

Processing and properties of

nonferrous metals

Study Support

Monika Losertová

Ostrava 2015

Title: Processing and properties of nonferrous metals

Code: PPNFM

Author: Monika Losertová

Edition: first, 2015

Number of pages: 113

Academic materials for two study programmes at the Faculty of Metallurgy and Materials Engineering: Materials Engineering and Economics and Management of Industrial Systems.

Proofreading has not been performed.

Execution: VŠB - Technical University of Ostrava

Content 1 Introduction to metallurgy

1.1 Technical classification of elements 1.2 Raw material sources for producing nonferrous metals

1.2.1 Classification of ores and minerals 1.2.2 Secondary raw materials and recycling 1.2.3 Ore dressing

1.3 Processes in metal producing 1.4 Purity of produced metals

2 Pyrometallurgical processes

2.1 Drying and calcination 2.2 Roasting

2.2.1 Oxidizing and sulphating roasting 2.2.2 Reduction roasting

2.3 Sintering 2.4 Smelting

3 Hydrometallurgical processes

3.1 Importance of hydrometallurgy 3.2 Basic hydrometallurgical processes and used equipment

3.2.1 Leaching and ores washing 3.2.2 Leaching methods 3.2.3 Separation of liquid and solid phases 3.2.4 Extracts cleaning

3.3 Special hydrometallurgical process 3.4 Principal characteristics of leaching 3.5 Separation of metals from aqueous solutions

4 Electrowinning process

4.1 Definition of electrolysis 4.2 Faraday’s laws of electrolysis 4.3 Electrolysis of aqueous solution 4.4 Electrolysis of melted salt bath 4.5 Electrorefining

5 Preparing pure metals

5.1 Chemical refining processes 5.2 Physical refining processes

6 Heavy metals

6.1 Basics of heavy metals 6.2 Copper 6.3 Nickel

6.4 Lead

7 Noble metals

7.1 Basics of noble metals 7.2 Silver 7.3 Gold 7.4 Platinum and platinum group metals

8 Light metals

8.1 Basics of light metals 8.2 Aluminum 8.3 Magnesium

9 Refractory metals

9.1 Basics of refractory metals 9.2 Titanium 9.3 Tungsten 9.4 Molybdenum

10 Dispersed metals

10.1 Basics of dispersed metals 10.2 Scandium 10.3 Lanthanum 10.4 Lanthanoids

11 Radioactive metals

11.1 Uranium

Introduction to metallurgy

1 Introduction to metallurgy

Before we start defining metallurgical processes, you should acquire the names for non-ferrous metals, which can be found in the tables. Currently, there are 91 known and named metals. However, it is necessary to mention that superheavy metals ranging from the atomic number 104 are very fragile and their preparation is the result of economically and time-intensive scientific experiments. A superheavy element will decay in an instant, so the technical applications for these elements as well as those ranging from the atomic number higher than the Pu (94) could not be expected so far. Their preparation is more important in terms of a study on the boundaries of atomic core stability and on finding evidence, to answer when the last set of protons and neutrons will hold together in a measurable period of time, and how the last element of the chemical elements table will look like.

1.1 Technical classification of elements Organizing elements in the periodic system, which respects the periodicity of properties and electron structure, can be found in the so-called Periodic table. For technical applications it is, however, more appropriate to distribute elements according to certain criteria, as it follows from Table 1.1. It is clear that these criteria are not unified, and that they relate to their physical, chemical, and nuclear characteristics, as well as to their occurrence in nature. It is possible to include some of them into two or more different groups, depending on what criteria are considered, see the schematic representation in Fig. 1.1. By comparing Table 1.1 with the periodic system of elements (Figure 1.2 ) you can also understand the relation of element positions in the table, and their grouping according to their characteristics. We will provide more detailed characteristics of each metal group in the following chapters.

Fig.1.1 Classification of selected metals according to specific critera

Study time: 2 hours

Objective When you have completed this module, you will be able to:

• classify the elements to groups according technical classification; • describe input materials in metallurgy • define different grades of purity of metals • define metallurgical processes

Lecture

Low density Corrosion resistance

High temperature strength

Noble metals (Au, Pt, Ag)


Fig.1.2 Mendelejev short table with elements / Tabulka ©2007 Jaromír Drápala, VŠB-TU Ostrava /, transactinoids are updated using [1]

Rg280

Cn 285

Uut284

114

Fl289

118

Uuo294

117

Uus294

116 Lv

293

115

Uup288

281 276 277 270 271 268 265


Table 1.1 Technical classification of elements [2, 3]

Group Metals

A. Iron and alloys Fe, steels, cast irons, Fe based alloys

B. Nonferrous metals and alloys

1. Heavy metals a) medium melting temperature: Cu, Ni, Co, Mn b) low melting temperature: Zn, Cd, Hg, Pb, Bi, Sn, Sb, Ga, In, Tl

2. Light metals a) medium melting temperature: Al, Mg, Be, Ca, Sr, Ba b) low melting temperature: Li, Na, K, Rb, Cs Note: sometimes Ti (4,5 g/cm3) is included

3. Noble metals a) medium melting temperature: Ag, Au b) high melting temperature: Ru, Rh, Pd, Os, Ir, Pt

4. High‐melting temperature metals

a) body centered cubic lattice: W, Ta, Nb, Mo, V, Cr b) hexagonal closed packed lattice: Ti, Zr, Hf, Tc, Re

5. Dispersed metals and lanthanoides (lanthanides)

a) dispersed metals: Sc, Y, La b) lanthanoides (at.No. 58‐71): Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,

Dy, Ho, Er, Tm, Yb, Lu

6. Radioactive metals, transuranium metals, actinoides ad transactinoides (actinides and transactinides)

a) natural radioactive metals: Po, Fr, Ra, U, Th, Pa, Ac b) transuranium metals and actinoides (at.No. 93‐103): Np, Pu,

Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr

c) transactinoides and superactinoides (at.No. 104‐168): Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg, Cn, Fl, Lv….?*

SEMI‐METALS (semiconductors)

B*, Si, Ge, As, (Se), Te, (Sb)*, (At+)*

NON‐METALS AND GASES

a) metaloides: H, C, N, O, (P, S), (B) b) non‐metals: P, S, Se* c) halogens: F, Cl, Br, J, (At+) d) inert gas: He, Ne, Ar, Kr, Xe, Rn+

Note: + radioactive elements (At, Rn) * www.webelements.com

1.2 Raw material sources for nonferrous metals producing Raw materials for producing metals may be ores or secondary metals (recycled wastes), which

are processed metallurgically either separately, or together, as shown in Figure 1.3). According to the content of metal (the metal of interest), which is to be extracted from ore (waste), the method of treatment is determined, as will be mentioned in the following chapters.


In addition to the resources in the earth, sea-water can be used for production of metals. However, the contents of metals in it are in relatively small concentrations, and thus the only metal that is obtained from seawater so far is magnesium.

Fig.1.3 Simplified schema of treatment

of primary or secondary sources

1.2.1 Classification of ores and minerals Ore as a complex raw material in its natural state contains minerals of interest, or eventually

other metals (e.g. galenite PbS, chalcopyrite CuFeS2), as well as slag (or gangue, i.e. a non-usable admixture of minerals or rocks). The representation of different minerals, their types and content, is determined on the basis of mineralogical analysis. From chemical analysis, the composition and the percentage of the metal of interest (the metalliferousness) is determined. From this follows the economy and efficiency of the further processing of the ore.

Some metals may be present in nature in their pure form. On the other hand, some of them are highly reactive and in the crust or in seawater they may occur only as compounds, e.g. as oxides, phosphates, etc. From the mineralogical point of view these compounds form minerals and systematic mineralogy divides them in accordance with their chemical composition and crystallographic structure into several groups (Strunz classification):

1. Elements 2. Sulphides (and sulfosalts) 3. Halides 4. Oxides, hydroxides (and vanadites, arsenites, antimonites, etc.) 5. Carbonates, nitrates, uranylcarbonates, sulfites, borates) 6. Sulfates, chromates, molybdates, tungstates, etc. 7. Phosphates, arsenates, vanadates etc. 8. Silicates, zeolites, germanates 9. Organic matter

For simplification we can classify minerals according to their chemical composition into four groups, as shown in Tab. 1.2.

In case the ore contains more metals of interest, it is a polymetallic ore, and it is possible, through successive dressing and metallurgical processes, to obtain these metals. In accordance with the metalliferousness in the ore they are divided into ores with high metal content, which are used for metal production with a minimum of additional treatment, and poorer ores, which are further refined to concentrates, or poor, whose processing is uneconomical. In general, ores with higher metal content are processed pyrometalurgically, poorer ores are proceeding into hydrometalurgical processes.


Table.1.2 Classification of minerals according to chemical composition

Forma Sloučeniny Příklad složení Pure metallic form Au, Ag, rarely Bi, Cu, Pt

oxides Cu2O, SiO2, Al2O3.nH2O, Fe2O3, SnO2, MnO2, TiO2 silicates Al2O3.2SiO2, LiAlSi2O6, Be3Al2Si6O18

carbonates CaCO3, MgCO3, BaCO3 SrCO3, ZnCO3, Na2CO3, CaCO3.MgCO3

sulphates PbSO4, CaSO4.2H2O, BaSO4 nitrates NaNO3, Ba(NO3)2

Compounds of oxygen

phosphates (La,Ce,Nd)PO4; Compounds of sulphur, arsenic and antimony

sulphides, arsenides, antimonides

Cu2S, CuFeS2, MoS2, PbS, ZnS, Ag3(SbS3), NiAs

Compounds of halogens chlorides, fluorides, etc. NaCl, CaF2, MgCl2.6H2O, AgCl, Na3AlF6 Some minerals are characteristic for their colours or interesting tradition, so that they are not

used only for metal production, but also in their pure form, or in different combinations in jewellery, in the manufacture of decorative items, as shown in Figures 1.4 to 1.8. A typical example is beryl with its chemical formula Be3Al2Si6O18, which is a raw material for the production of metal beryllium, and in its dark green variety it is known as the gem emerald (Figure 1.7 ); zirconium with chemical formula ZrSiO4, which is used to manufacture metal zirconium, or in its yellow-orange form as the germ hyacinth, and in its white form as a jargon in jewellery or technical industries.

Fig.1.4 Minerals of copper: a) chalkopyrite and b) cuprite

Fig.1.5 Mineral of magnesium magnezite a) natural form, b) decorative and c) jewellary applications

a)

a)

b)

b) c)


Fig.1.6 Aluminum ore: a) deposit of bauxite in Guinea –Conakry and b) compact piece of bauxite composed of minerals of: Al, Fe, Si, V etc. (collection of dpt. Of Geology - Brigham Young University, Provo, Utah)

Fig.1.7 Mineral of beryllium: a) common beryl a b) and c) different variety of beryl (dark-green emerald)

Fig.1.8 Mixed minerals a) dolomite (extraction of calcium or magnesium) and b) coltan (tantalum and niobium)

In nature mixed minerals often occur as well, such as dolomite or coltan (Figure 1.8 ). Dolomite

is a carbonate mineral containing calcium and magnesium (CaMg(CO3)2), from which metals are gained after treatment using electrolysis or thermal reduction.

The term coltan is used for a matted black mineral (Figure 1. 8b) which is formed by columbite tantalite, from which we obtain niobium and tantalum. A mineral containing niobium is called columbite (therefore the first part is „col“), and tantalum is contained in tantalite, which represents the

a) b)

b)

c) a)

b) a)


other half of this term. Niobium and tantalum are gained using leaching, extraction, and mutual separation and subsequent reduction. Coltan is considered to be a bloody mineral and the reason of many conflicts; for more details see below. Niobium and tantalum are currently being used on a large scale in the production of electronics for capacitors (mobile phones, computers, games consoles, etc. ).

Why coltan is called a bloody mineral? On the basis of a UN report, coltan is considered to be a so-called conflict mineral. First, it is necessary to be aware that both tantalum and niobium are used to produce capacitors, which are the parts of small electronic components, in particular mobile phones, notebooks, gaming consoles, and other electronic devices. With the growing progress and expanding market this lucrative trade with valuable coltan is also growing for these products. This mixed mineral is located in large quantities in the Congo, from where 80 % of this mineral comes from world mining. Mining is a highly organised, systematic industry, but in many cases it is illegal.

The first negative fact associated with coltan is the fact that in the Congo they use child labour for mining. This work is very poorly paid, and working conditions are devastating for a child's organism.

Another downside is that the mining and sale of these minerals enrich and finance various parties, playing their roles in local civil wars in this area. For example, according to one UN report the army of neighbouring Rwanda earned by the sale of coltan 250 millions of USD in less than 18 months, although no coltan is being mined in Rwanda. Military groups in Uganda and Burundi are also involved in the sales of smuggled coltan. This coltan is then sold to Belgium. Also companies producing mobile phones (Samsung, Sony, Motorola, Nokia, Alcatel, etc. ) cannot confirm that their suppliers of small electronic components, which occur in mobiles, did not use for the production the"bloody" coltan from the Congo.

Finally, a third and equally important dark side is the impact on the environment and the live nature. The mining of coltan threatens gorillas, elephants, and other rare species, not only in African War Zones, but also areas protected by law, such as e.g. Kahuzi-Biega National Park (KBNP) in the Democratic Republic of the Congo. Deposits of coltan are located in numerous places in Kahuzi-Biega Park itself and for the local communities living around the park its mining is a highly lucrative job. Thousands of people are moving to these areas, to mine both around and inside this park. Up to 12,000 people mine in the park illegally. At the same time the people of the Congo receive only a fraction from the sale of raw materials. As it was already mentioned above, this commercial and material profit from the mining primarily motivates various military groups, which are involved in civil wars in this region. In the occupied areas, people experience looting, plundering, and extortion, and the other activities of criminal cartels with international contacts, which is a very serious security problem, not only for a given area. No one can count exactly how many of the 3,600 elephants and 8,000 gorillas have survived the massacre of animals in this area. We can only hope that endangered populations have survived or retreated into less accessible and mining-free areas. According to the official data from this area they say that 350 elephants were killed and half of the 258 gorillas. Indirect data shows, however that the stock of gorillas only in Kahuzi-Biega and Kasese has decreased below 1,000 individuals! This represents a loss of 80 to 90 percent! Also other protected areas are in a very similar situation. Mining and poaching has also an enormous impact on biodiversity (the diversity of species), which was very seriously damaged in Kahuzi-Biega, if not irrevocably destroyed.

But in fact, by recycling, these requirements for the mining of primary raw materials can be significantly reduced. A relatively well-known campaign of collecting mobile phones, organised by non-profit organizations in cooperation with zoological parks, by which the UN increases awareness of this problem, gives everyone an opportunity to participate actively. For every mobile phone, collected in this campaign, a certain part of this amount sponsors various projects to save gorillas. Functional phones are for example resold, non-functional ones are recycled, and valuable minerals are used again. This step alone can contribute to a reduction in demand for coltan.

1.2.2 Secondary raw materials and recycling Waste utilization in metal manufacturing brings considerable savings in power. In some cases,

this may represent more than 80 % of the initial costs (Table 1.3 ). The most significant savings are in aluminium production, where the use of recycled materials brings up to 95 % of energy savings. After steel, aluminium scrap is the most reused scrap material. In addition, with the increase in prices of


metals the recycling of those metals pays off, even for those whose processing was unprofitable before. New technologies are also contributing to a better use of metals.

Table 1.3 Proportion of recycled metals in new produced metals and energy saving [4]

Recycled metal New metal produced using

recycling (%) Energy saving

(%)

Aluminum 39 95

Copper 32 85

Lead 74 60

Steel 42 62‐74

Zinc 20 60

Recycling of scrap metal currently represents up to 50 per cent of the return on metals. According to the phase of waste formation we can divide them into three types (Fig. 1.9): Production or circulation waste comes from a company´s own production (slag, meissens, fly

ashes, solutions) Processing or new production waste, resulting from further processing (splinters, chips, scraps) Consumer waste or depreciation waste, including appliances and devices from households or

from businesses

Among the most important consumer waste containing metals, which have been successfully recycled, are:

• Packaging: each year billions of beverage cans made of steel or aluminium alloy are recycled. • Cars: more than 75 % of materials in the car are made from different metals. Approximately half

of the recycled materials comes from used cars (Fig 1.10a to 1.12 ). • WEEE (waste electrical and electronic equipment): the majority of discarded household appliances

is now being recycled. Electrotechnical and telecommunication appliances contain a significant share of various non-ferrous metals (Cu, Al, AG, au, PT, Hg, Pb, lanthanides, etc. ). The biggest problem is currently represented by those energy-saving compact fluorescent lamps (so-called energy saving bulbs) (Fig. 1.10c ) and sources with LED diodes, which are like linear fluorescent lamps with a mercury content (one compact seems to contain 5 mg Hg), and other heavy metals (Pb, Cu, Ni etc. in electronic chips for sources with LED diodes). They should also be recycled as hazardous waste. Unfortunately, knowledge of this problem is at a very low level among consumers, according to the sources of EKOLAMP [5], s.r.o. in 2011 some 23 % of households disposed of linear lamps, and 27 % of compact lamps, and 14 % light sources with LED diodes. In a year 902 tonnes of light sources were handed over for recycling, under which we can imagine more than 6 million linear and compact fluorescent lamps, tubes, LED lamps and light sources. Compared to 2012 , a million more light sources were collected, so calculated in toxic mercury, some 30 kgs less of this toxic metal got into wild nature.

• Batteries: An EU directive is valid since 2008, but previously lead-acid car batteries and other industrial batteries were recycled. The main problem has been and still remains the personal responsibility of citizens to submit batteries and accumulators (NiCd, NiMH, Ni-Fe, Ni-Zn, Li-ion, Li-Pol, RAM, Na-S etc.) as hazardous waste to collection points.

In theory, any metal can be regained from scrap metal and used again, but the recycling technologies and obtained purity differs according to the metals, as specified in the following overview:


Steel scrap is processed in the steel industry as the main charge in electric arc furnaces, and the obtained recycled material is used to produce high-quality tool steel or stainless steel. A smaller quantity of scrap may be used for production in blast furnaces. Copper scrap is reused by primary and secondary producers; technologies include melting in

the shaft, reverberatory furnaces, or electric arc furnaces. The latter allows to process charges with up to 75-80 % of copper scrap. Aluminium scrap is melted in a crucible furnace, rotary drum, or shaft furnace at

approximately 660°C, which is significantly less than for primary production using reduction electrolysis (above 900 °C, Hall-Heroult´s process). Recycling one ton of aluminium material saves approximately 4 tonnes of bauxite (the main raw material for aluminium production), 95 % of the energy needed for the production of primary aluminium, and 9 tons of CO2 emissions. Recycling aluminium currently saves more than 80 million tonnes of greenhouse gas emissions per year. This is equivalent to approximately 15 million cars[6]!

The availability of secondary aluminium is still very low. Of all sectors, the rate of aluminium recycling is highest within the construction industry, ranging between 92 and 98 %, followed by the automotive industry with 95 %, and 50 % in the packaging industry. So far, only 40 % of the demand of the world market for recycled aluminium is met. More than 75 % of aluminium material produced in the last 100 years is still in circulation. Recycled aluminium is used e.g. for construction materials, food packaging, components for the automotive industry, etc.

Recycling of magnesium is much more difficult than the previous cases. The majority of magnesium scrap comes from foundries (from pressure casting) and allows a reduction of demand on primary input material for foundries up to 50 %. The quality of scrap, especially ones originating from the automotive industry (ELV scrap) must be checked, as magnesium can be contaminated by Fe, Ni or Cu, which have a very negative effect on its corrosion resistance. Reduction of Fe content is carried out by adding Mn; Ni and Cu concentrations are reduced by using distillation or dilution, both of which represent economic demands on energy and new material. Remelting magnesium alloys with a controlled content of ingredients and impurities will consume only 50 % of the energy necessary for the distillation. The development of magnesium recycling and a recycling line are shown in Figures 1.13 and 1.14.

Lead scrap is melted in a shaft furnace or a minor-waste drum with a content of lead in a drum furnace. At present, the most important source of recycled lead are lead-acid batteries, both in our country and on a global scale. Over 50 % of the world´s lead is produced by recycling (60 % in Western Europe and 70 % in the US). They estimate that recycled lead production in percentage is much higher than that of paper, plastic or glass, which is often associated with differences between the prices of raw materials and the cost of processing waste material for the latter mentioned. In manufacturing lead from recycled materials the need for energy is only for 35-60 %, in contrast to production using ores Recycling car batteries (Figure 1.15 ) is also a significant environmental step, as it reduces the undesirable transition of lead into the environment, and it maintains mineral resources for the future. Although it would be possible, according to some estimation, to recycle at least 85 % of the consumed lead, in reality this volume of recycled lead is lower. There may be several reasons for that, the main role is played by economic profitability and practical side of the process. Here are some issues to get an idea of the importance of the largest consumer of the lead, which is the battery industry nowadays. For example, for the production of accumulators (not only for cars) there is used in Western Europe 57 % and in the USA 80 % of produced lead. Average European car batteries weigh 13 kg, of which more than half (7.6 kg) is lead, and their life expectancy is usually approximately 4 years (for stationary batteries the lifetime is longer up to 10 years). From these figures it is clear that the recycling of lead is very important. It must be added that the rate of collection and the return of the accumulators is very high in most states of the EU, even though the data on the quantity of recycled lead-acid batteries are available only in a few countries [7].


Recycling noble metals is currently a very important process, because they are used not only in jewellery, and as a reserve or an investment commodity, but also in other technical sectors of human activity. In the present industry, for its specific qualities all noble (also called precious) metals have been applied to a certain extent, i.e. , silver, gold and platinum group metals (Ru, Rh, Pd, Os, Ir, Pt). Relatively large quantities of these metals are to be processed in the automotive industry, namely 35 % of their total annual consumption, and then manufacturing products for electrical engineering. Noble metals are also applied in medicine, which uses e.g. the anti-allergic or anti-bacterial properties or silver or cytostatic effects of platinum in the treatment of cancer. Silver is the most processed metal. For example, in the Czech industry its consumption reaches around 150 tonnes per year, followed by gold (10 tonnes), platinum (8 tons), palladium and rhodium. Because of the high price of these metals their recycling is very important, which means recycling equipment and objects containing them. In 2012 in the Czech Republic a hundred tons of silver were recycled, as well as five tons of platinum, three tons of gold, 2.5 tonnes of palladium, and 0.2 tonnes of rhodium. More than half of our domestic demand for silver and platinum is covered by recycled metals, in the case of gold it is roughly a third. The volume of precious metals recycling in the last ten years has grown, for example, in the company Safina, a.s. the increase is around 20-25 %. Obtaining precious metals and other metals from electrical waste and electronic equipment (WEEE) uses procedures today, which are at the same time able to meet all parameters of WEEE material recovery, stipulated by Law No 7/2005 Coll., on waste. Treatment of WEEE shall be preceded by a relatively technologically and investment undemanding pre-treatment, which includes mainly manual dismantling, subsequent removal of WEEE substances, and their presorting, as required by the law on waste. From these devices all printed circuits must be removed, together with the cables, and all dangerous substances, which may cause contamination during the subsequent mechanical processing of the whole batch. Pre-treated waste is crushed and ground, subsequently separated using magnetic and Foucault separators, with ultimate sorting by a fluid vibration vanner. This introduced procedure allows us to recycle not only the required share of metals, but also to reuse plastic materials that constitute a relatively significant percentage of WEEE weight. The subsequent processing of metallic fractions can be performed using either pyrometallurgical technologies (Varta - in a shaft furnace), hydrometallurgical (cyanide leaching), or electrometallurgical (electrolytic refining). Progressive processing of discarded products is shown in Fig. 1.16, in which there is a chart showing the processing of old catalytic converters using Tetronics plasma technology, which enables the processing of car catalytic converters and the catalysts in the chemical and petrochemical industry containing metals of the platinum group (e.g. platinum, palladium, and rhodium), with the lowest impact on the environment. In our country a company dealing with the recycling of precious metals is SAFINA, a.s. in Vestec. In recent years, the big challenge is the mastering of technological operations for efficient and

cost-effective recycling concerning very strong magnets based on rare-earth metals (Nd, Sm), into which the producers are pushed due to price increases and restrictions on exports of the metal from China.


Fig.1.9 Schema of exploitation and processing of primary and secondary sources


Fig. 1.10 Exemple of waste recycling on the base of Fe, Al and Cu: a) wreck cars, b) beverage cans and c)

electro-waste.

Fig. 1.11 Utilisable waste material of different car details

Fig. 1.12 Schema of wreck car recycling

a)

b)

c)

1-sedadla (polymery, vlákna) 2-okna (sklo) 3-kapota (oceli, hliník) 4- motor (oceli, hliník, hořčík) 5- dráty vodičů (měď) 6-motorové oleje 7-chladiče (měď, hliník) 8-chladicí kapalina 9, 14 – nárazník (plasty) 10- bateria (olovo) 11-převodovka (ocel, hliník) 12-plechy (ocel, hliník) 13-kufr (ocel, hliník) 15, 21-pneumatiky (kaučuk) 16- dveře (ocel, hliník) 17-katalyzátor (Pt kovy) 18-olej převodovky 19-pérování (ocel, hliník) 20- kola (ocel, hliník)


Fig. 1.13 Graph of world primary producing and recycling o Mg from twenties of 20 th Century

with prognosis to 2150 [8,9]

Fig. 1.14 Schema of EFRS-500 recycling line of Mg and Mg alloys. Electrotherm Fluxless technology is used in recycling of automotive Mg materials (AZ91D (Mg-Al-Zn), AM60 (Mg-Al-Mn) and new Mg alloys alloyed with alkali metals or lanthanoids) [10]


Fig. 1.15 Schema of recycling process of lead auto battery

Fig.1.16 Schema of recycling noble metals from catalytic converters [11]

Výrobce baterií

Blok olova

Kontrola jakosti

Neutralizace kyseliny

Olověný ingot

Polypropylen

Kovové olovo

Nová baterie

Oxid olovnatý

Přední nárazník

Separátor

PecAfinace

Odlití

Drcení a mletí

Stará baterie


Why metal recycling is important?

Recycling metals is a fast growing sector, which stands at the top of the imaginary pyramid of all industrial sectors. It contributes more than any other, by collecting products after their lifespan, to achieve an objective based on prevention in waste policy, and maintains a clean environment not only for human society, but also for animals and plants. In the United Kingdom you can find employed over 8,000 people in the industrial sector processing non-ferrous and ferrous metal scraps. The number of employees engaged in recycling metals in the Czech Republic is currently not known, but the significance of this sector is increasing. On the worldwide scale, more than 400 million tonnes of metals are annually recycled. Authorised packing company EKO-KOM, which has been founded by industrial companies producing packaged goods in 1997, effectively operates, as a non-profit joint-stock company, a statewide sorting system, recycling and recovering packaging waste up to a high-quality European level. For the whole complex of activities undertaken by this company the term "EKOKOM system " was generally accepted. As packaging materials we use metals, paper, glass, plastics and the others, as shown in Figure 1.17. The percentage representation of the different materials used by clients of the EKOKOM system to pack their products has not changed over the years. Thanks to the cooperation between industry, cities, and towns in the Czech Republic one-fifth of household waste and over two-thirds of all packaging is recycled. In the Czech Republic, the most recycled packaging is paper, followed by glass, metals, plastics, and beverage cartons, as shown in Figure 1.18. The total rate of recycling packaging waste by the EKOCOM system is equal to 72 % of packages placed on the market. As we have stated in the preceding paragraphs, waste processing and recycling includes not only their sorting, but in particular chemical and metallurgical operations. At the end we get sorted materials, which can be re-used for the production of various products. Our technical civilization, which is based on science and technology progress, more and more hustle and bustle in the consumer carousel, which unfortunately brings in more and more waste. After the handling of all necessary technological operations and a highly mature approach of citizens our society should be able to produce and recycle products in a closed cycle with great energy savings, as well as raw materials savings and the reduction of CO2 emissions, and with an environment-friendly attitude to the outside world. Unfortunately, this is not the case yet, and so a large percentage of unsorted waste ends up in landfills, waste banks or in the sea, as shown in Fig. 1.9 The ecological aspect of recycling is required not only in relation to nature and the environment, but also with respect to ourselves, because the vast majority of non-ferrous metals is somehow toxic to animals or plants. Waste, which ends in the soil, may with wrong placement contaminate ground water or plants, and wastes floating in the sea or oceans are falling to the seabed, intoxicating the food chain of all marine organisms. In all of these cases we are standing at the imaginary top of the consumption of these contaminated natural resources for our livelihood! So we should keep in mind that with each PET bottle, appliance, battery, or energy saving bulb discharged to a landfill we increase a risk of contamination for the environment, and increase the risk of diseases with cause tumours.

Fig. 1.17 Structure of disposable packages in 2013 [12]


Fig. 1.18 Structure and recycling rate in 2013 [12]

1.2.3 Ores dressing Non-ferrous metal ores are less metalliferous, part of its ore constitutes a barren rock, or tailings,

so the direct metallurgical processing is uneconomical and technically difficult. As we have mentioned before, ores of non-ferrous metals are complex polymetallic, and they must be treated before the processing (Fig. 1.19). Treatment of mineral sources does not alter the chemical composition of ores, but by removing spoils it increases the percentage of the metal of interest. Among the fundamental treatment processes of ores belong the following operations:

Grinding - mechanical disconnection of minerals and spoils in an ore by crushing and milling, with possible subsequent sorting, depending on particle sizes in the semiproduct.

Separation - the process of enriching, based on the various properties of each constituent of the processed ore (e.g. according to its density, magnetic properties, wettability etc.), which increases the metalliferousness of the ore.

Agglutination - or sintering, which represents the treatment of tconcentrate for pyrometallurgy.

Grinding With grinding or milling the size of rocks or ore particles is reduced. The biggest pieces, which

come for treatment, can reach 1,000 - 1,500 mm, but the final grain size can be only several micrometers. From this it is clear that the fineness of graining can be reached by milling and grinding during several phases, and it is done using various types of devices (Fig. 1.20). In the following Table 1.4 the grain-sizes of individual types after crushing or grinding are summarised. Table.1.4 Methods of crushing or grinding and resulting granularity of ores

Separation (disintegration) of the solid body into pieces using mechanical methods, is done by mechanical forces acting on the particle cohesion forces of the body. The basic principles of crushing include spalling (strikes), mashing (pressure), spreading and splitting. A brief specification of the devices that are using the different principles of material desinteraction, is shown below:

Jaw crushers - grind the material between stable and movable jaws. Cone crushers - continuously grind material between two concentric cones. Cylindrical grinders - material is disintegrated between two cylinders rotating against each other. Hammer crushers - process ore using the strikes of hammers or rods. Edge-runners - continuously grind and spread material by rotating heavy wheels on a solid circular plate. Ball and rod mills - material is crushed by freely falling balls or rods.

Type of comminution Final granularity (mm) Coarse crushing > 125 Middle crushing > 25 Fine crushing < 25 Grinding < 1.25 Fine grinding < 0.08


Fig.1.19 Schema of copper ore dressing

Fig. 1.20 General view of crushing and

grinding line with separation [8]


Degree of grinding (milling) with (Table 1.5.) is expressed by the ratio average of the largest pieces before grinding (milling) to the average of the largest pieces after milling (grinding):

dDs =

where D - is a diameter of the largest pieces or grains before disintegration, d - diameter of the largest

grains in the resulting product

Table 1.5 Grade of grinding for different types of milling devices

Sorting the ore into classes based on grain-size is done when material is falling down though

the area with regular holes, i.e. through grates or sieves in wet or in dry conditions. Grates are composed of fixed or movable parallel profile rods, sieves are formed by either a perforated steel plate or wire mesh. The class of grain, which falls through the holes of the grates of sieves, is called sieve fraction, or sub-sieve class (factions), the ones which remain in the sieve or grate are oversized particles (fractions).

Sorting can be divided according to purpose into several types: 1. Auxiliary - before a crusher there are grate or sieve places, which sorts out grains smaller than the

size of the dump hole of the crusher, and thus increases the efficiency of crushing (Fig. 1.20).

2. Preparatory- milled ore should be divided into classes according to the size of grains and each class should be treated separately.

3. Final - ore is sorted into classes according to sizes. 4. Selective - in case a mineral differs from the spoils as to its hardness, it is possible to perform

sorting by dissociation.

Effectiveness of sortingη t (in %) is defined as the ratio of the quantity of the sub-sieve B to the quantity of the same size (as the sub-sieve) A of the material at the start of the process. If the sieve has the size openings d then in the sieve there will be an amount of oversized particles greater or less than in d:

100⋅=AB

tη

The effectiveness of sorting is determined on the basis of the sieve analysis of average samples for an input ore and oversized fractions:

( )( ))100

10000ba

bat −

−=η

Where a is the content of grains smaller than d in the starting ore (in % ), b is volume of grains smaller than d in oversized fractions.

Device Grade of crushing (grinding)Jaw crushers 5 ‐ 6 Cone crushers 5 ‐ 20 Crushing rolls 3 ‐ 10 Hammer crushers 10 ‐ 15 Rod mills 12 ‐ 30 Ball mills 50 ‐ 100


Separation In separation useful minerals are separated from the spoils on the basis of different physical and

physical-chemical properties and a concentrate is formed. The chemical composition of a mineral or a state of matter will not change, there is only significant ore enrichment, i.e. an increase of its metalliferousness. In the event that an ore contains more metals of interest (a polymetallic ore), it is a collective concentrate from which individual metals need to be obtained using combined methods. If such a concentrate can be further separated, it is necessary to prepare a selective concentrate, which will allow us to utilize every metal of interest by simpler processes. The selection of the method for separation depends on the

1. technical requirements for the products of selection 2. difference between composition and characteristics of the mined ore 3. dissemination of minerals 4. mineralogical composition of ore and characteristics of minerals 5. value of commercially used minerals

Dissemination is often uneven, for this reason, therefore, more than one method is used for separation.

Methods of separation

a) Manual sorting - the oldest and simplest method, based on the distiction of a mineral according to its colour, spar, or the shape of the pieces (directly in a mine, or on the belts);

b) Ore washing - removing clay ingredients using their distraction in water, which will allow its separation from bigger grains;

c) Gravitational separation on jiggers - based on the difference in the vertical speed of the minerals falling in an alternately ascending and descending flow of water; one condition here is a sufficiently large difference in the density between the spoil and mineral;

d) Gravitational separation on vanners - uses a different specific weight of ore ingredients, on which in the longitudinal axis a thin layer of water flows down the vanner plate with a slight tilt, equipped with grooves, which causes vibration movements.

e) Separation in heavy liquids - a liquid environment (aqueous solutions with salt, organic liquids, aqueous suspensions) has lesser density than the density of one component, and greater than the other components of ore. The lighter spoil or minerals float, heavier minerals fall to the bottom. The advantage is effective and accurate distribution, the great performance of separation devices, the easy adjustment of the density suspension; it does not require pre-sorting, with the possibility of the simultaneous sorting of grains from 5 - 100 mm, as well as regeneration of the suspension. The disadvantage is unsuitability for fine-grained materials. Heavy suspension separators: a pyramid with mechanical haulage, a rotary -internal thread conveyor, conic-haulage by compressed air.

f) separation in an electric field - uses different electrical properties (conductivity), separator types in accordance with an electric field: electrostatic discharge or brush discharge;

g) magnetic separation - based on different magnetic properties; the particles are brought into the magnetic share, fighting mechanical forces (gravity, friction, adhesion, environmental viscosity), (Fig. 1.21), example of usage: sorting Sn-W ores and separation of Fe;


Fig.1.21 Schema of dry electromagnetic separation device [8] h) flotation - based on the different physical-chemical properties of minerals and spoils in ores, and in

particular on different wettability; a process suitable in particular for poor polymetallic ores and for secondary raw materials.

The wettability In interfaces between a liquid and a particle so-called wettability takes place, which depends on the

surface tension of the given liquid and the character of the surface of a mineral particle, which is determined by the free surface energy of the atomic and molecular links. The quantity, by which we can determine whether or not the material is wetted, is a tangent angle θ between a liquid and substrate (spoils, mineral). When a drop of liquid is applied to the the material surface it takes a shape in which all forces acting on the phase interfaces are at equilibrium (Figure 1.22):

Θ⋅+= cosLGSLSG γγγ

whereγ LG is the surface energy between the liquid and air, γSG is a surface energy between the mineral (spoil) and air andγ SL is the surface energy between a mineral (spoil ) and liquid.

Fig.1.22 Angle of the wettability of a liquid on the mineral surface Depending on the size of angle we distinguish: θ = 0° ……perfect wettability θ < 90 ° ……..good wettability θ > 90 ° ……. bad or no wettability

Flotation

Flotation as a separation process for minerals is based on different abilities of mineral grains to adhere and stabilize itself on the interface of the phase boundary. The position, which the particle takes as to the phase boundary, is determined by only the value of specific surface energy in existing phases. At the same time, in agreement with the second theorem of thermodynamics the whole system must reach a state corresponding with the minimum of free energy (Fig. 1.22). The varied ability to keep mineral grains on the surface of the different phase interface results from the differences of specific surface energy values. The value of the specific surface energy is a function of a chemical composition and of a structural matrix construction .

In practice, most important is foam flotation, in which used for measuring the difference in specific surface energy for coexisting phases in the non-plane surface interface - i.e. in the whole volume of ore pulp, saturated with air bubbles, which connect with ore grains and takes them to the surface of pulp creating the mineralized foam = flotation foam. For the floatation of ore we need: pulp - an aqueous suspension of finely grained ore, of granulation smaller than 0.1 mm.


flotation reagents - increasing the necessary properties of metalliferous grains, as well as the flotation environment;

air supply - for the aeration of pulp.

Classification of hydrophylicity (good wettability) and hydrophobicity (bad wettability) of solid substances surfaces in the air is based on the contact angle θ (Fig. 1.22):

1. an absolutely hydrophilic surface - on which the aqueous drop completely melts and pushes air out (θ =0, cos θ=1);

2. a partly hydrophilic surface - water partial pushes air out, θ the angle is sharp; 3. a partly hydrophobic surface - air partly pushes water out and θ the angle is obtuse; 4. an absolutely hydrophobic surface - complete spreading of air, (θ= 1800 , cos θ = - 1 ),

practically such surfaces do not exist.

During flotation the following actions take place: 1. flotation agent shell the grain of material with a thin monomolecular film 2. similarly, flotation agents shell the air bubbles, pulled into pulp 3. ore grain with a coating of flotation agents becomes attached to the air bubbles 4. an air bubble carries the ore grain into the surface foam 5. spoil grains remain, also wettable in the pulp 6. the foam with ore grains is separated from the rest of the pulp

During the flotation process flotation additives play an important and decisive role, which are divided into three groups, according to their characteristics and the effect during flotation:

collectors - organic substances, which use absorption performed on the surface of a mineral to create a film, which decreases wettability; foamers - agents which reduce surface tension at the interface of gaseous and liquid phase,

stabilizes air bubbles and thus the foam on the surface of pulp. As foamers synthetic alcohols, oils, organic acids are used; controlling additives that affect selective flotation, which also include:

o depressors - agents suppressing the floatability of certain minerals o activators - agents revitalizing

flotation ability to violate the layer of depressors

o regulators - agents modifying flotation ability by regulating the oncentration of hydrogen ions in pulp. Alkalinite adjustment using hydroxides or whitewash, acidity using using H2SO4.

The process of flotation is significantly affected not only by the selection of appropriate flotation agents, but also by their dosage.

Devices which are used for flotation and which allow for continuous process by the fluid supply of pulp and draining of the foam product, are so-called flotators. Types of flotators can be divided according to their air inlet for the creation of foam:


agitational (mechanical) - with a stirrer, which absorbs the air pneumatic - pressure injection of air combined - air supply and stirrer.

Fig.1.23 Schema of flotation device [8]

By combining several flotators we get a flotation battery. The technology of flotation procedures can usually be varied, in principle it is subject to the general schemas of selective and collective flotation ( Fig. 1.23). After flotation drainage and drying is carried out, the liquid is piped out for recirculation.

Flotation is carried out for very finely ground particles 0.2-0.1mm, and according to their floating ability we can divide the minerals into: - easily floated: copper ore, stibnite, molybdenite, galena, sphalerite, pyrite, argentite; - floatable: magnesite, cobaltine, Fe-ores, cerussite; - hard floating: bauxite, V, and W ores, oxide copper ores, rutile; - very hard to float: cassiterite, chromite, titanite.

Agglutination Processing of the products after treatment, which contain dust particles and which would be

inappropriate for further pyrometallurgical processing, is carried out using agglutination (the sintering) of fine-grain ores and mineral concentrates):

1. Briquetting 2. Pelletising 3. Sintering (agglomeration)

Briquetting

The agglutination process of fine-grain ore is carried out by applying high pressure up to 150MPa, with the possible introduction of additives (binders). Suitable binders cause not only the agglutination effect, but also enables the reducution of the consumption of fuel or slag-forming additives (for example pitches, tars, limes).

Pelletizing

Very fine-grain ores and concentrates (lumpiness under 0.5 to 0.2 mm) are suitably wetted and put into spherical formations (pellets) in a peletization device (with a rotating drum or plate). Good pelletising is the result of capillary forces, so initial humidity plays an important role, optimally with the quantity of water ranging at about 10 %. The strength of pellets is increased by adding binders (Fig. 1.24), and in particular by burning or by sintering (with added 2 % of coke).


Přívod materiálu

Odvod aglomerátu

Ohřev

skrubr

Fig.1.24 Pelletization process [9]

Sintering

Sintering (agglomeration) is a heat-chemical process, in which ore grains melt, agglutinate, and cake. The heat source is represented by burning sulphur, contained within the material. If the material does not contain sulphur, the material is mixed with fuel (coke, mazut, etc.) before its agglomeration.

The aim of the sintering process is to cake batches into pieces suitable for further processing and eliminate excess sulphur from the concentrate, but a required content of S must be maintained, which has to be enough only for agglutination and not to melt down.

The whole process takes place on a caking belt on which dust particles of ore or concentrate lie. These are at first blown on the surface e.g. with a gas flame, and gradually, as they move through the air, the hot zone moves slowly across the entire layer of the charge. The charge is moving slowly on the belt, the grains on the surface soften, creating bridges between one another, they stick together and at the end of the machines we get a sinter (Fig. 1.25).

Between the gas and solid phase during agglomeration there are exothermic reactions, during which heat necessary for sintering and desulphurisation is released:

2MeS + 3O2 = 2MeO + 2SO2 MeO + SO3 = MeSO4

Sintering processes include thermal processes, involving also a change in the chemical composition of the core ore components into a soluble chemical compound. In these cases the main objective is a change of chemical composition.

Fig.1.25 Schema of sintering line Requirements for the agglomerate: • sufficient porosity - permeability for reducing gas emissions • high strength • resistance to crushing and abrasion • self-density - corresponding composition for further processing (required sulphur content, slag-

forming additives to ensure self-melting and maintaining slag basicity) • required sulphur content - for further processing Charges in lumps and dust forms are represented by: • metalliferous raw material (ore, concentrate), • returnable material (waste, intermediate products - dust, ash, sludges), • additives affecting the progress of sintering (limestone, sand, pyritic spent grain), • or fuel

1.3 Processes in metal producing Main processes Secondary processes

Dressing processes (removal of mine debris and accompanying elements)

Hydraulic washing Gravity separation Flotation Magnetic separation


Ore concentration without chemical reactions Chemical separation

Přeměna upravených surovin na jiné sloučeniny (oxidy, chloridy, ….)

Calcination (carbonates, hydrates…) Pražení (sulfidů,…)

Reduction of compounds (oxides, ..) to metal

Roasting – HgS +O2 = Hg + SO2 Reduction – reducing agents of higher oxygen affinity then reduced metal Electrollytic reduction

Refining

Electrorefining – Cu, Au, Ag, Sn, Pb, Cr, Ni. Sweating – Sn, Pb, Bi Distilling ‐ Zn,Hg Oxidizing – Fe, Cu

Processes, in which the metal, which was chemically bound, is separated from the ore, or further deprived of an admixture (refining) is part of metallurgical operations. Processes are carried out due to physical and chemical reactions under certain conditions. For instance, pure metal may be obtained in the form of powder, sponge, melt or condensate. In Table 1.6 there is a basic summary of processes carried out in metallurgy. These processes will be dealt with in more detail in the following chapters.

1.4 Purity of produced metals After melting we get a raw metal that contains a certain amount of unwanted ingredients of

metals, non-metals or gases, which may interfere with the properties of metals, metal alloys, or other materials that are prepared on the basis of these metals. From these properties, which depend on the content of unwanted elements, we can mention e.g. electrical, mechanical, corrosion, and other properties. It can be further treated and cleaned, and thus we receive a metal of a higher purity. The following tables show the characteristic contents of impurities for a given semi-product or a resulting metal (Table 1.7). Refining (cleaning) is possible to carry out using various methods (using fire refining, electrolysis, distillation, directional crystallization, etc.), which of course further increases the utility value ofa metal, but at the same time also its price. Table 1.7 Grades of purity in produced metals

Denotation of metal (type of process or refining) Content of impurities

Raw metal (melting) 3‐5 %

Technically pure metal (pyrometallurgical refining) Up to 1 %

Electrolytically refined metal (electrolysis) Up to 0.5 %

e.g. cathodic Cu, Ni, Co, Zn, …

Metals for purpose‐made (special methods of metal preparing or refining )

spectral, physical, semiconductor or nuclear purities

Purity levels and impurities can be indicated as a percentage, but it is often possible to find it in

commercial areas and in scientific activity labelling using N in the case of a basic metal or using ppm or ppb in the case of impurities, as it is shown below, to transfer relations (Table 1.8 and Table 1.9 ).

Table 1.8 Van Arkel denotation of purity, so called nonary designation Denotation Centent of besic metal in wt.%

Above Below 1N 90 99 2N 99 99.9 3N 99.9 99.99


4N 99.99 99.999 5N 99.999 99.9999 6N 99.9999 99.99999 7N 99.99999 99.999999

Table 1.9 Denotation of impurity content (extra low concentrations)

Summary of terms

Periodic system, ores, concentrates, waste, recycling, crushing, milling, separation methods, flotation, agglutination, agglomeration, pelletizing, briquetting, metallurgical processes, purity of metals

Question to the topic

1. Which groups of metals you can list from point of view of technical applications?? 2. Which metals are called light metals? 3. Which natural radioactive metals do you know? 4. Which group of metals represent Au, Ag and Pt? 5. Can you list two basic raw sources for producing nonferrous metals? 6. Can you designate the types of minerals? 7. What is the raw ore? 8. Why is necessary to make dressing of ores to concentrates?

What resources can you use to help?

[1] DRÁPALA, J., KRIŠTOFOVÁ, D., PEŘINOVÁ, K. Těžké neželezné kovy. Návody pro cvičení. Skripta

VŠB Ostrava, 1986,197 s. www.Webelements.com [Cit. 2013-08-15] [2] KUCHAŘ, L. Hutnictví neželezných kovů. Ostrava, VŠB 1987, 335 s. [3] http://www.recyclemetals.org/about_metal_recycling) [4] http://www.ekolamp.cz/ [Cit. 2013-08-15] [5] Recyklace hliníku. Online na http://www.reynaers.cz/cs-CZ/noviny/recyklace-hliniku/, [Cit. 2013-08-15] [6] www.olovo.eu/soubor/vlastnosti-olova [Cit. 2013-08-15] [7] http://www.intlmag.org/magnesiumsustainability/recycling.cfm [Cit. 2013-08-15] [8] http://www.roperld.com/science/minerals/magnesium.htm [Cit. 2013-08-15] [9] http://www.electrothermindustry.com/efrs-500 [Cit. 2013-08-15] [10] Tetronics Platinum Group Metal Recovery Process. Online na http://www.azom.com/article.aspx?

ArticleID=10922 [Cit. 2013-08-15] [11] http://www.ekokom.cz/cz/ostatni/vysledky-systemu/vyrocni-shrnuti [Cit. 2013-08-15] [12] ŠTOFKO, M., ŠTOFKOVÁ, M. Neželezné kovy, Košice, 2000, 293 s.

1 ppm (corresponds to 6 N purity of basec metal) 10-4 wt. % of impurities 1 ppb (corresponds to 9 N purity of basec metal) 10-7 wt. % of impurities

http://www.recyclemetals.org/about_metal_recycling

http://www.olovo.eu/soubor/vlastnosti-olova

http://www.intlmag.org/magnesiumsustainability/recycling.cfm


[13] Agglomeration. Dostupné z <http://www.ipc-dresden.de/ index.php?option=com_content&view =article&id=40&Itemid=19&lang=en> [Cit. 2013-08-15]

[14] DRAPALA, J., KUCHAR, L. Metalurgie čistých kovů-Návody do cvičení. Skripta VŠB Ostrava, 1990, 165 s.

[15] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [16] SCHMIEDL, J. Hutníctvo neželezných kovov. Bratislava: Alfa, 1984. 280s. [17] http://www.intlmag.org/magnesiumsustainability/recycling.cfm [Cit. 2013-08-15] [18] http://www.roperld.com/science/minerals/magnesium.htm [Cit. 2013-08-15] [19] http://www.electrothermindustry.com/efrs-500 [Cit. 2013-08-15] [20] Tetronics Platinum Group Metal Recovery Process. Online na http://www.azom.com/article.aspx?

ArticleID=10922 [Cit. 2013-08-15] [21] http://www.ekokom.cz/cz/ostatni/vysledky-systemu/vyrocni-shrnuti [Cit. 2013-08-15] [22] Video linky na recyklace autovraků http://www.faguspraha.cz/zemedelska-technika/drtice-a-separatory-

hammel_/jemne-drtice-na-kovovy-odpad-hammel-rady-hem_.htm [23] HABASHI, Fathi. Handbook of extractive metallurgy, VOL. 2-4. Weinheim: Wiley-VCH, c1997, ISBN 3-

527-28792-2. [24] Gupta Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.

KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6 [25] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5 [26] Schlesinger, M E., King, M. J., Sole, K.C., Davenport, W. G. Extractive Metallurgy of Copper 2011

Elsevier Ltd., 472 s. ISBN: 978-0-08-096789-9 [27] ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys Edited by J.R. Davis, ASM International,

2000, s. 362-370. ISBN: 0-87170-685-7 [28] Handbook of Aluminium. Volume 1. Physical Metallurgy and Processes. Ed. by TOTEN, E.G., Mc

KENZIE, D.S. New York, 2003, 1296 s. ISBN: 0-8247-0494-0 [29] Friedrich, H. E., Mordike B.L. Magnesium Technology. Metallurgy, Design Data, Applications. Springer-

Verlag Berlin Heidelberg, 2006. ISBN-10 3-540-20599-3 [30] Titanium and Titanium Alloys. Fundamentals and Applications. Ed. by Cristoph Leyens and Manfred

Peters. Wiley-VCH GmbH&Co.KGaA, 2003. ISBN 3-527-30534-3 [31] LASSNER, E., SCHUBERT, W-D. Tungsten .- properties, chemistry, technology of the element, alloys,

and chemical compounds 1999, Kluwer Academic / Plenum Publishers, New York 434 s. ISBN 0-306-45053-4

[32] MOSER, K.D. The Manufacture and Fabrication of Tantalum. JOM, April 1999, s. 29-31 [33] DRÁPALA, J. and KUCHAŘ, L. Metallurgy of Pure Metals. Cambridge International Science Publishing

Ltd., 2008. [34] Rare Earth Elements online na http://www.bgs.ac.uk/downloads/start.cfm?id=1638 ‎ [Cit. 2013-08-20] [35] GUPTA, Ch. K. Extractive Metallurgy of Rare Earths 2005, CRC Press, s.484. ISBN 0415333407

http://www.intlmag.org/magnesiumsustainability/recycling.cfm

Pyrometallurgical processes

2 Pyrometallurgical processes

The aim of the pyrometallurgical processes is to transfer a required material using physical

processes at higher temperatures to one phase and separate the impurities (the non-miscible phase, other components of the same state). This operation is used for processing simple compounds and raw materials with higher metalliferousness Among basic pyrometallurgical processes (Fig. 2.1) are: 1. Drying and calcination 2. Roasting 3. Sinting (agglomeration) 4. Melting 5. Sublimation and distillation 6. Thermal degradation (thermic reduction) 7. Refining (e.g. by change of solubility solidification)

2.1 Drying and calcination Concerning the elimination of water from the ore we must distinguish between drying and

calcination processes. Drying is the elimination of free water, or another solvents, and thus it is lowering the wetness and creating so called. dry matter.

During calcination (also dehydration, dissociation) we remove chemically bound (crystal, hydrate) water or eventually chemically decompose some hydrates, carbonates, sulphates and other compounds, or eliminate volatile components. As an example we can take the following equation for calcination: removal of chemically bound water (dehydration) – an example here is the dehydration of

bischofite MgCl2.6H2O → MgCl2.4H2O → MgCl2.H2O 117 ˚C 185 ˚C thermal decomposition – or dissociation of compounds- is the dissociation of compounds to

simpler ones in a system of solid states (s)/gas (g) at higher temperatures. This is a endothermic reaction. As an example we can mention the reaction of the carbonate (magnesite) decomposition to oxides:

MgCO3 → MgO + CO2 The rate of decomposition is determined by the diffusion of components and size of a reaction area. A basic parameter to determine the feasibility of reaction is dissociation (disintegrative) temperature, at which the tension of a released gas corresponds to the atmospheric pressure (1atm. = 0.1 MPa):

Tdis = ΔH/ΔS lnKp = ln[pCO2] = - ΔG/RT

Study time: 2 hours


• define the aim of pyrometallurgical process; • describe basic classification of pyrometallurgical processes; • list the types of smelting processes; • describe melting products.

Lecture


Fig..2.1 Row of pyrometallurgical processes

Fig. 2.2 Dissociation pressure of selected carbonates and hydroxides in function of temperature


From the thermal dependence of the partial pressure of CO2(H2O) for the mentioned compounds in the Figure 2.2 is possible at pCO2(H2O)=1 atm to read disintegrative temperatures e.g. for carbonates MgCO3 (410°C) or CaCO3 (910°C).

2.2 Roasting During this process there is a change in the chemical composition and physical properties of the

basic raw material (ore or concentrate), necessary for further metallurgical processing (pyrometallurgically or hydrometallurgically). The roasting process is carried out at elevated temperatures, but such in which no melting of material is taking place. During the process there is a reduction of the sulphur content, the valency of elements may vary, converting from complex to reducible compounds. Roasting is a reaction between the gas and condensed phases (heterogeneous reaction), therefore, its progress affects mainly the atmosphere within the furnace. According to the nature of the gaseous atmosphere in a furnace, or to the composition of the resulting products we divide roasting into:

1. oxidation 2. sulphation 3. reaction

chloridation segregation chlorination and fluoration

4. reduction

Parameters of roasting

The efficiency of the roasting process depends on the following factors: thephysical and chemical properties of the roasted material (e.g. , humidity of starting raw

materials) degree of grinding (particle size) temperature of the process quantity of air or gas (e.g. the amount of oxygen needed for the combustion of sulphur and

oxidation can be calculated stoichiometrically, with regard to the composition of charges) the mixing of roasted material the technical parameters (output) of the furnace

It is necessary to control and monitor the process, roasted ore is monitored for its e.g. desulphurisation level, presence of sulphidic sulphur, physical properties, etc.

2.2.1 Oxidizing and sulphating roasting The process of the oxidation roasting belongs among the widespread processes. The objective

here is to convert metal sulphides with the access of air in an appropriate furnace to oxides, which are reduced to metals under further metallurgical operations. Sulphation roasting is carried out in the case that the subsequent step in processing the raw material is a hydrometallurgical operation (leaching), since most of the sulphates are water-soluble.

The higher the affinity for oxygen, the more easily will the roasting reactions be held. According to the temperature and atmosphere of roasting we can divide roasting into: • the direct oxidation of simple sulphides (or arsenides and antimonides) to oxides with a general

equation of exothermic reaction: MeS + 3/2 O

2 → MeO + SO

2 + Q

2 MeAs + 5/2 O2 → 2 MeO + As

2O

3 + Q

• oxidation to sulphates or sulphation, which is performed similarly to oxidation roasting; the final step, however, is the emergence of a sulphate in compliance with the summary equation:


2/32

2

Opp

K SOp =

log

p SO

2

log p O2

2 MeS + 4 O2 → 2MeO + 2SO2 + O

2 → 2MeSO4

Equilibrium of the process, which is expressed by the equilibrium constant:

is shifted to the right side of the equation, oxidation roasting is therefore at commonly used temperatures (500-1,000 degrees °C) an irreversible process. The process of oxidation can continue, but gases must be continuously conducted away from the reaction space.

The equilibrium and predominant area for the complex system Me - S - O at a constant temperature is displayed in Kellog´s diagrams which allow, if necessary, the selectection of the gas phase composition for roasting. In the diagram (Fig. 2.3 ), the condensed phases MeS, MeO , Me, MeSO4 and the gaseous phases O2, SO2.

Fig.2.3 Equilibrium and

predominant areas in Me-S-O system at constant temperature

Obr.2.4 Příklad výskytu predominantních oblastí v systému Cu-S-O při různých teplotách: 727, 827 a 927°C.(Převzato z databázového výpočtového systému FactSageTM,

http://www.crct.polymtl.ca/factsage/fs_predom.php)


Lines in the diagram, which represent the balance between any two condensed phases at a given

temperature (Fig. 2.4 ), represent the reaction in the system described by the following equations: Me + SO2 = MeS + O2 2 Me + O2 = 2 MeO 2 MeS + 3 O2 = 2 MeO + 2 SO2 2 MeO + 2 SO2 + O2 = 2 MeSO4 MeS + 2 O2 = MeSO4

Side processes in oxide roasting

1. Complex sulphides are decomposing (dissociate) and the pollutants of degradation are oxidising (an example can be the roasting of chalkopyrite CuFeS 2)

2. Certain metal sulphides may change during dissociation to the pure state of a metal at the release of sulphur (e.g. vermilion HgS and occurrence of mercury)

HgS → Hg + 1/2 S2 3. Sulphation of oxides at the formation of complex compounds

SO2 + 1/2 O2 = SO3 MeO + SO3 = MeO.SO3 = MeSO4

4. Vaporizing of volatile oxides (e.g. As2O3) 5. Lower oxides are oxidising to higher 6. Metal oxides may be reacting with SiO 2 at the forming of silicates

MeO + SiO2 = MeO. SiO2 = MeSiO3 7. Metal oxides may react with Fe2O 2 duringthe formation of ferrites (ferrates, MeO.Fe2O 3), which

may have a negative impact on the further processing of roasted ore using the hydrometallurgical method.

8. Roasting reaction processes, during which a proportion of non-oxidised sulphide in reaction with oxides or sulphates reduces to the metal. This process is undesirable, because in the case of metals with a low melting temperature (Pb) the furnace grates may be flooded with a new liquid metal.

Conditions during sulphation roasting

In the course of this type of roasting the sulphide concentrate it is necessary to control the temperature and gas phase composition. The emergence of sulphates takes place predominantly at lower temperatures than in the case of oxidation roasting, because lower temperatures allow the emergence of SO3 oxide, which is an important and controlling link to form sulphate.

2.2.2 Reduction of roasting Gradual reduction of the oxides valency up to reducing metals takes place during reduction

roasting in an environment of reduction gases (CO, H,2, CH 4 .) According to the theory of adsorption-catalysis we can divide roasting in terms of the process mechanisms into three stages:

1) reduction gas is absorbed on the surface of an oxide 2 ) from he metal oxide the oxygen is separated and it is transferred into the reduction gas (CO, H 2)

with formation of CO 2 (or H2 O), and the crystalline network of a new metal Me phase 3 ) release (desorption) and displacement of the reduction products CO 2 (or H2 O) from the surface

of a new phase The whole process is expressed by equations:

MeO(s) + CO(g) = MeO(s).CO(ads.) MeO(s).CO(ads.) = Me(s).CO2 (ads.) Me(s).CO2(ads.) = Me(s) + CO2(g)

Summary: MeO + CO (H2) = Me + CO2 (H2O).


Reduction is a reversible process and the reaction, which represents the reduction from the left to the right and oxidation from the right to the left, defines the size of this value Δ G:

2MeO ⇔ 2Me + O2 (ΔG1) 2CO2 ⇔ 2CO + O2 (ΔG2)

Summary: MeO + CO ⇔ Me + CO2 (ΔG) For reduction of oxides (ΔG < 0, kdy ΔG2 > ΔG1) is valid:

.)()(22

rovnppg

pp

CO

CO

CO

CO > a )()(22

MeOpgP OO <

At oxidation of metals (ΔG > 0, kdy ΔG2 < ΔG1) is given:

.)()(22

rovnppg

pp

CO

CO

CO

CO < a )()(22

MeOpgP OO >

For effective reduction the reaction equilibrium must be shifted to the right in the direction of metal and CO 2 occurrence.

Reduction gas is a mixture of reducing components (CO, H2 ) and oxidation (CO2 , H2O); therefore, by regulating the components in this mixture we can regulate this reaction intensity. Metal oxides have different dissociation pressures, which are used to choose a correct reduction atmosphere for selective reduction.

Reduction roasting by hydrogen is carried out at relatively low temperatures, the purity of the reduced metal depends on the purity of the starting oxide. The product of hydrogen reduction is a powdered metal, and water vapour.

Equipment for roasting

a) b)

Fig. 2.5 Roasting furnaces: a) storey and b) fluidization furnaces


Roste hustota

Devices used for roasting are universal and may be used for each type of roasting. Regarding the lumpiness of the final product we can divide it into those in which the product is a powdered roasted ore, and those in which the roasted ore is formed in pieces. For effective roasting we must ensure the good contact of a roasted ore with the gas.

For the preparation of powdered roasted ore we use furnaces (Fig. 2.5 ): Storey Rotary For roasting in levitation melting For roasting in a turbulent layer (fluidization)

2.3 Sintering The sintering process or agglomeration has been already dealt with in Chapter 1.2.3, but we

must not forget the thermal processes, which are included in sintering processes, as they are used to treat poor ores for further hydrometallurgical processing. In this process there is a change of the chemical composition and the transition of the metal of interest into a soluble compound. As an example we can mention the processing of bauxite ores by sintering to prepare oxide Al2O3, which goes on further to electrolysis (Chap. 8,.2 ), the sintering of wolframite concentrates with soda during the formation of soluble sodium wolframate, which is further processed into powdered tungsten (Chap. 9.2 ).

2.4 Smelting To separate metal components from the spoil the raw material is heated up over the melting

temperature T m of the metal of interest, so there are physical and chemical changes taking place, the metal of interest undergoes a reduction, and its particles concentrate into the melt, spoils are removed which goes into the slag. The two main stages are, therefore, a reduction of metal and the removal of spoils.

The products of melting are typically two liquid phases (the interest metal melt and slag). Sometimes (depending on the content of elements in the raw material), there are three or more liquid phases (Speise, Matte), which are separated from each other based on different physical and chemical properties: specific weight, melting temperature, viscosity, mutual solubility and miscibility, the surface tension on the interface of phases. Fig. 2.6 shows a diagram of the deposit of emerging liquid products of melting depending on their density. Other products may be gases and fly ashes. Smelting products (in a state): 1. metal (solid, liquid): with a certain content of impurities; 2. slag (solid, liquid): a mixture of oxides of metal and non-metal elements, a small

quantity of metals, metal sulphides and gases; 3. matte (liquid): results from the concentrated

melting of sulphides as an alloy of metal sulphides with a great affinity to sulphur;

4. speise (liquid): arises from concentrated melting rather as an undesirable product consisting of the antimonides and arsenides of metals, which cannot be easily recovered (metal losses);

5. fly ashes (gaseous, liquid); 6. gases ((gaseous): CO2, H2O, SO2, N2, SO3.

Fig. 2.6 Liquid products of smelting We divide the smelting processes depending on whether the final product is a metal compound or a raw metal:


(a) Smelting with metal compounds formation 1. concentration smelting 2. coagulation smelting 3. dissociative smelting

(b) Smelting with metal formation 1. thermal reduction processes 2. reaction smelting 3. reducing displacement smelting 4. oxidation smelting - converting 5. refining melting and remelting 6. electrolytic melting and others.

(a) Smelting with compounds formation

Concentration smelting

In this way of melting unroasted or partially roasted raw materials, the metal concentration occurs in the form of compounds in semi-finished product, which must be further processed. The concentration of melting is used with heavy non-ferrous metals having a high affinity for sulphur, or with antimony and arsenic. - heavy non-ferrous metals with high affinity to S concentrate into the sulphidic semi-final product - matte. Practically for all mattes a common component is sulphide FeS, and a certain amount of oxygen bound to FeO. Types of mattes

Copper - Cu2S + FeS Nickel - Ni3S2 + FeS Copper-nickel Lead-copper

Basic reactions in matte between metals Me1 and Me2 is Me1O + Me2S = Me1S + Me2O Practically, with copper matte the reaction takes place: Cu2O + FeS = Cu2S + FeO The resulting oxides enter the slag. In addition to copper the noble (expensive) metals also enter the matte, e.g. tin, lead, part of antimony, arsenic and bismuth, which does not evaporate, and also a greater part of nickel. Approximately half of cobalt and zinc, and the vast majority of iron passes into slag. - non-ferrous metals with a high affinity to Sb and As concentrate to speise - a semi-finished product, formed by antimonides and arsenides. The formation of compounds As and Sb (Ni3As2, Ni5As2, Ni5Sb2) is usually undesirable, as their processing is both economically and technically demanding, and dangerous in terms of the environment.

Coagulative melting

In this type of melting the agent excludes a certain part from the melt, which is obtained and further processes. Among operations that are using precipitation process are included: Kroll-Betterton method - removal e.g. Bi from lead - PbBi(tav) +Ca → Pb + Bi3Ca (Pb3Ca) Jollivet method - (Mg, K) → Bi7Mg6K9 Parkes method (Parkes process) - removal of Ag and Au from lead

PbAuAg (liq) + Zn → Ag2Zn3, Ag2Zn5 , AuZn, Au3Zn5, AuZn3

These compounds have a higher melting temperature, lower density and do not mix with each other, so they are floating up and are wipped off (so-called scums) from the surface of the wash.

Dissociative smelting

By adding assistants (a so-called flux) there is a change of state of the matter and a change of chemical composition in ores and concentrates. For this type of melt the ores must be pre-processed as for


hydrometallurgal processes, therefore, there must be a transfer of an insoluble mineral into soluble and infusible compounds. According to the nature of fluxes we divide melting into acid and alkaline.

(b) Smelting with metal formation

Thermal reduction smelting

To recover metal we use reducing agents (reducers), predominantly at high temperatures. This way mainly reduces metals from their oxides (Fe, Sn, W, Ta, Ni, Mn, Cr) or from halides (Ti, Zr). If the metal occurs in sulphide form, at first it should be converted to oxides (Pb, Zn, Mo), and only then their reduction into metal will take place. Reducers (R) are all substances capable of withdrawing oxygen from anoxide:

MeO + RO(g) → Me + RO2 MeO + R(s) → Me + RO Gaseous reducers - H2 for the reduction of pure highly-meltable metals -W, Mo, Re from their pure oxides or preparation

of pure Fe, Ni, Bi and Co, more effective at a higher temperature; – CO for the reduction of Ni, Cr in a carbornylic process, more effective at lower temperatures; – methane CH4;

Solid reducers - C, CaC and other metals with higher electronegativity than reduced metals Dissociation pressure in response to the degradation of oxides according to the equation may be calculated using an equilibrium constant: where aMeO2 and aMe are the activities of oxides and the pure metal and P O2. is the partial pressure of oxygen. During thermal dissociation of the equilibrium pressure of oxygen, which is in equilibrium with the decaying compound, it is represented by dissociation stress. If the participants of the process will be only the pure components, then their activities are in a solid form of the constant and, Kp applies

Standard change of free energy: ΔGo = - RT ln Kp = - RT ln pO2 ΔG = RT (ln p*O2 - ln pO2)

For decomposition the dissociation temperature T dis is determined, which represents the temperature at dissociative pressure pO2 101,325 Pa (atmospheric pressure). The stability of oxides is the measure of a metal´s nobility; the higher the dissociation pressure, the more noble the metal is (Au, Ag, Pt). If the metal is able to constitute more oxides, then gradually the thermic decomposition occurs:

MeO2 → Me2O3 → Me3O4 → MeO → Me Binding of the released oxygen is done using reduction substances, which have greater affinity for oxygen than the reducing metal. The ability of substances to bind oxygen can be evaluated using the Δ G emergence of oxides at different temperatures.

In order to determine the stability of a given metal and temperature of degradation using various reducing agents we base it on the Ellingham-Richardson diagram (Fig. 2.7), which indicates the temperature dependency of the standard molar free energy (Gibbs energy) ΔGO for formation of the oxide. Ellingham diagrams (Ellingham, 1944) are phase diagrams, which use for their construction

2

2

2

2

OMeO

MeOp p

aap

K =⋅

=

2Op pK =


two chemical potentials (oxygen O2and RTlnpO2 ) and temperature. The more negative the value ΔGO of the reaction is, the more stable the oxide is. If the element is formed by several oxides, the lowest are always the most stable: e.g. FeO in case of Fe→ FeO → Fe3O4 → Fe2O3.

The less stable oxides in the diagram in Figure 2.7 only occur in the upper part, the medium stable in the middle part, and the very stable occupy the lower part of this diagram. Even in the least stable oxides by mere thermal decomposition it is possible to reduce only the oxides of the precious metals (Ag, Pt, Pd); all the other oxides need for their reduction to metal is to add a reduction reagent.

Basically, any element, which the Ellingham line is situated below the Ellingham line of a given element, is able to reduce the oxide of a given element to its elemental form. In practice, for the reduction of metal oxides there are used in particular non-metals (such as carbon or hydrogen), semimetals (Si), or some of the selected metals (such as Ca, Mg, and Al). Diagram represents the thermodynamic driving force of the specific reactions throughout a whole range of temperatures. Ellingham-Richardson diagrams are used to determine systems with the following properties:

1. Relative thermodynamic stability A-AOx-B-BOy 2. Thermodynamic stability A-AOx, degradation pressure O 2 3. Thermodynamic stability A-AOx-CO-CO2 4. Thermodynamic stability A-AOx-H2-H2O

The reaction rate during the reduction of metals can be controlled using the following factors: 1. the properties of charges with reduced metal oxide in terms of mineralogical composition,

lumpiness and porosity of the ore, the homogeneous content of a metal oxide in the processed ore. 2. temperature reduction 3. composition of the reducing gases (or mixtures of gases) 4. the speed of gas penetration through the charge and piping out resulting CO2 from the non-reacted

CO. Reducing processes of metals and alloys production, which are using solid reduction agents and take place at high temperatures, can be divided regarding the possible intake and heat consumption into autothermic processes (with own reaction heat) and electrothermic (using electric furnaces). In terms of reducing agents we can divide thermal processes into: 1. Carbothermic processes The reducing agent is carbon in the form of coke, coal, graphite, or the pure soot. The reduction of metal oxides difficult to reduce using carbon at high temperature follows the reaction:

MeO + C ⇔ Me + CO Application: o preparation of metal Nb, or eventually V and Mo o preparation of Ti and Zr alloys, or pre-alloys with other transition metals o production of ferro-alloys- FeCr, FeMn, FeW, FeSiCr o preparation of pre-alloys of transition metals by reduction from the mixture of oxides Ta-V, Ta-W,

V-Cr, Nb-V etc. o use in connection with the chlorination - production of Ti, Zr Reduction of metal oxides by carbon may take place either as

o Direct reduction - reaction between solid metal oxides MeO and carbon: or as

o Indirect reduction - reducing by gaseous reducer CO; • it is much faster than reduction using solid carbon, because gas covers particles and at the same

time it penetrates their pores • consuming CO at occurrence of CO 2 • CO regenerates from CO 2 by adding solid reducers (carbon, coke, etc. ). - Boudouard reaction • kinetics of this reaction is determined by either the chemical reaction speed (low temperatures), or

the diffusion speed (high temperatures)


Fig. 2.7 Richardson- Ellingham’s diagram with plots of oxide stabilities for different metals


2. Metalothermic processes Reducing agent to reduce compounds of metals from their oxides or halides is another metallic element with a higher affinity for a given element of compound (oxygen, chlorine, sulphur, etc. ):

o Al – aluminothermic process, o Mg – magneziothermic process, o Si – silicothermic process, o Ca – calciothermic process, o Na – sodiothermic process.

Application: Magneziothermic process - preparation of Be, Ti, Zr, Hf, U, Sk, Th and others. Calciothermic process - reduction of oxides of V, U, Cr, Ti, Th, Pu

reduction of halides U, Th, Pu, Sk, dy, Nd, Ga, La, Z, Ce Silicothermic process - production of Mg using ferrosilicon - Pidgeon process

Summary of terms

Drying, calcination, roasting, matte smelting, reduction smelting, dissociative smelting, matte, speise, Ellingham-Richardson diagrams, metalothermic processes.


1. Can you explain the differences between the drying and calcination? 2. Can you define the principle of smelting? 3. Which product is formed during concentration smelting? 4. What is expressed by plots in Ellingham-Richardson diagrams? 5. Which product of smelting do you know?


[1] HABASHI, Fathi. Handbook of extractive metallurgy, VOL. 2-4. Weinheim: Wiley-VCH, c1997, ISBN 3-

527-28792-2. [2] ELLINGHAM, H. J. T. Reducibility of oxides and sulfides in metallurgical processes. Journal of the Society

of Chemical Industry, London 63, 1944, s. 125-33. [3] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [4] RICHARDSON, F.D.; JEFFES, J.H.E. The thermodynamics of substances of interest in iron and

steelmaking from 0 to 2400°. I. Oxides. Journal of the Iron and Steel Institute, London, 160, 1948, s. 261-70.

[5] Ellingham Diagrams. http://www.doitpoms.ac.uk/tlplib/ellingham_diagrams/partial_pressure.php [Citation 15/8/2013]

[6] Gupta Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6

[7] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5

[8] WILLIS, G. M., TOGURI, J. M. Yazawa’s Diagram. The AusIMM Metallurgical Society Special Paper, September 2009, s. 1-8

[9] Schlesinger, M E., King, M. J., Sole, K.C., Davenport, W. G. Extractive Metallurgy of Copper 2011 Elsevier Ltd., 472 s. ISBN: 978-0-08-096789-9

Hydrometallurgical processes

3 Hydrometallurgical processes

3.1 Importance of hydrometallurgy Hydrometallurgy is the process of extraction from poor or complex ores (Cu-ore, Ni-ore,

obtaining U, V, Au,..). Hydrometallurgical procedures are also used in recycling metals from scraps. Principle

Processes of hydrometallurgy represents the extraction (the washing out) of one or more commercially used metals from raw ore or modified ore using solvents. One condition must be the increased solubility of metals, which we want to extract, or the increased solubility of undesirable ingredients that would spoil solutions.

Preparation of material for leaching 1. Mechanical ore dressing - crushing, grinding (below 0.5 - 0.1 mm) 2. Roasting heat treatment (sulphation, chloridation, oxidation, reduction or sintering with chemical

ingredients), so that the metal is transferred to a soluble compound, the solubility of undesirable ingredients is limited

Classification of solvents by chemical character: 1. water - leaching metals in the form of sulphates (Cu, Zn) 2. acid - diluted acids

H2SO4 - extraction of oxygenic compounds or metal components HNO3 - leaching Mn HCl - Zn, Ni-Co-ores

3. principles NaOH, Na2CO3, - Cr, U

diluted solutions (NH4)2CO3 - leaching metals 4. salt aqueous solutions

cyanides (NaCN), - leaching Au, Ag chlorides (NaCl, FeCl3) leaching Pb, Cu

Choosing the right leaching solution (solvents) according to the following requirements: quick dissolving of leached minerals (the economic point of view) minimum corrosion effects on leaching apparatus minimum dissolving of spoils eventual selectivity in regard to the leached ore low price ability to regenerate (only the refilling of losses)

Study time: 2 hours


• define the aim of hydrometallurgical processing; • describe basic principles of hydrometallurgy • list the types of solvents • explain basic hydrometallurgical processes

Lecture


3.2 Basic hydrometallurgical processes and used equipment Schematically the hydrometallurgical processing is shown in Figure 3.1 and includes the following processes:

1) leaching and washing ores 2) separation of the solid and liquid phase (leachate and leach residue) 3) cleaning of leachate 4) extracting metals from solutions

Fig.3.1 Schema of hydrometallurgical processes


3.2.1 Leaching and ores washing (a) in leaching the components of desired ore transferred into the solution, and the metal in its soluble form dissolves in a suitable solvent. Starting materials of this process are, therefore, the leach solution and enriched ore, the product of leaching is the leachate and leach residue.

In order for the metal concentration in the extract to be as high as possible, the ratio between the solid and liquid phase (K: p) must be as small as possible. The ratio K:P of slime = ratio of the liquid and solid phase

The following physical parameters have an impact on the course of leaching

temperature pressure concentration of agent granularity of material and surface conditions of the solid phase intensity of contact between an ore and solution (agitation)

(b) by washing leached ore the trapped leaching solution is removed from the waste sludge Efficiency of leaching processes will be increased through the following parameters:

1) intensive mixing of the slime (suspension in the leaching solution) 2) granularity of material under 1 mm

3.2.2 Leaching methods As to the method of leaching and devices (or other agents) we can implement leaching as: 1. Underground (in-situ) leaching, which is used in particular for poor deposits of Cu, U and Au, it

is possible only under specific and favourable geological conditions.

2. Heap leaching using sprinkling with water or diluted H2SO4, e.g. for poor deposits of U.

3. Leaching by solutions leakage, or percolation (as well as diffusion) is used for ores with greater granularity or for pellets, which can be easily leached in tanks.

4. Agitation leaching, which is carried out in tanks, is more efficient than the previous processes. A significant influence is the ratio of K:P.

5. High-pressure leaching is carried out in a closed pressure vessels - autoclaves with different structures and different heating.

6. Bioleaching when under the co-action of leach and micro-organisms the hard soluble sulphides are oxidizing and transfer to easily soluble sulphates. Among micro-organisms, used in leaching, there belong thiobacillus ferrooxidans, thiobacillus thiooxidans, parasitic micro-organisms, molds, yeasts, algae, and other organisms.

Equipment

mixers - covered or open cylindrical tanks with a stirrer pachuka - high cylindrical tanks, the supply of the compressed air in the form of bubbles stirs

the slime, also called air lift reactors. percolators - closed cylinders, its perforated bottom is covered with ground ore leaching columns autoclaves - pressure vessels

Terms: lixiviant (leaching reagent) = leaching solution leachate = solution obtained after leaching leach by-product = insoluble residue of leaching


According to the motion of the leaching solution the leaching process can take place as: uniflow - solution is advancing through a device in the same direction as the ore counterflow - solution is advancing through a device against the direction of the ore

movement Washing takes place as a counterflow process.

Fig.3.2 Underground leaching of uranium ores (http://powerofnuclear.blogspot.cz/2010/10/nuclear‐fuel‐cycle.html) Fig.3.3 Typy autoklávů: a) svislý autokláv s mechanickým mícháním; 1-dávkovací trubka, 2-výpustní trubka, 3-ohřívací had; b) vodorovný jednokomorový autokláv; c) baterie autoklávů s mícháním a dopravou rmutu pomocí reakčního plynu: 1-míchač, 2-čerpadlo, 3- výměník tepla, 4-odlučovač, 5-kolonový autokláv, a-čerstvý rmut, b-kyslík nebo vzduch, c-pěna, d-plyn a pára, e-vyloužený rmut


3.2.3 Separation of liquid and solid phases The solid phase is represented by undissolved ore remains, various precipitatea, etc. The separation process of this phase from the liquid should be ensured using:

sedimentation which is carried out in settling tanks, thickeners, hydrocyclones, in which the thickening of fine dissolved particles takes place (coagulation and floculation), during the process it is possible to use a floculation agent (electrolytes or organic agents) filtration, which divides the slime into filter cake and filtrate by passing it through a porous

barrier (filter) and it may take place as o pressure in a sludge press or in leaf filters o avacuum with the vacuum filters

centrifugation - advantageous if the quantity of the solid phase is significantly larger than the liquids

o filtration, which is carried out using pressure filtration and centrifugal force o sedimentation, which according to the different specific weight of the particles and of

the solution splits both phases into the cake and the fluid refining solutions shall be carried out before the precipitation of metals by chemical agents or

before reducing through electrolysis using sand filters, sludge presses etc.

Concepts: filtrate = filtration solution cake = particles on the filter

3.2.4 Extracts cleaning Before the subsequent processing of leachate and the extraction of metal(s) from solutions, cleaning should be carried out using the following methods:

o By precipitation the harmful ingredients are converted to insoluble compounds and filtered. This method is used for a hydrolytic type of metal precipitation.

o The liquid-liquid extraction based on the different solubility or reactivity of individual metals in organic solvents.

3.3 Special hydrometallurgical processes Autoclave processes - are all carried out at increased temperature and pressure, thus accelerating chemical processes and some of them cannot take place at all

o leaching under pressure o precipitation of metals under pressure

3.4 Principal characteristic of leaching • The speed of leaching increases with decreasing granularity (the smaller the particles, the greater

the specific or reaction surface). • If leaching is controlled by diffusion, the leaching speed depends on the intensity of mixing,

which must maintain levitating the solid share. • The speed of leaching increases with increasing temperature. • With an increasing concentration of the leaching agent the speed of leaching is also increasing

(NOTE: optimum concentration). • The speed of leaching depends on the share of solid content in the slime, it grows with a

decreasing share of K: P. • If during the leaching process there are insoluble products occurring, the speed of leaching

depends on their character. Leak-proof products reduce the leaching rate.


3.5 Separation of metals from aqueous solutions Obtaining metals from aqueous solutions after leaching should be carried out using the following methods:

1. Crystallization, which represents the cooling of a saturated solution or solvent evaporation with a consequent loss of crystals from the oversaturated solution

2. Distillation precipitation, in which there is heat degradation e.g. the amino carbonates of copper and nickel, carbonates up to the oxides.

3. Sorption of metal by sorbents, whether physical (using van der Waals forces) or by chemical reactions and the surface of solid phase, for example, on coal.

4. Cementation, which is the process of metals precipitation in a solution, in which the nobler metal is driven out from a solution of its salts by a less nobler metal , which is dissolved. The process is an oxidation/reduction electrochemical process, which is expressed by the following equation:

Me1 + +Me2 0 = Me2 + + Me1 0 E2 < E1

where eE 1 and E 2 are the electrode potential of metal Me 1 and Me 2.

Metals are sorted according to their potentials into the so-called Beket series of elements potentials: Li Rb K Cs Ba Sr Ca Na Mg Be Al Mn Ti Zn Cr Fe Cd In Tl Co Ni Sn Pb H2 Bi Cu Os Ru Ag Hg Pt Au The problem will be explained in more detail in Chapter 4 (Electrometallurgy).

5. Reduction of metals by gases (H2, CO, SO) is carried out at high temperatures and pressures

6. Electrolysis of aqueous solutions, in which using insoluble anodes brings a current into the electrolyte solution, and they reduce on the cathode the metals of interest.

7. Ion exchange, which uses ion exchange capacity (or cation exchange resin, or anexy) to exchange in contact with aqueous solution ions of the same sign.

8. Solvent extraction, in which the substance of interest is gained from the aqueous solution in the form of the liquid organic phase (solvents), which should not be mixed with water, and then the metal is extracted by re-extraction into the aqueous solution.

Summary of terms

Leaching reagent, autoclave leaching, bioleaching, leachate, filtrate, leaching parameters, Beketov serie of elements potentials, ion exchange, solvent extraction.


1. Describe the stages of hydrometallurgical process. 2. What is the principles of hydrometallurgy? 3. Define the difference between the leachate and leach by-product? 4. Which factors are influencing the leaching rate? 5. Co je principem cementace?




527-28792-2. [2] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [3] Gupta Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.



Elsevier Ltd., 472 s. ISBN: 978-0-08-096789-9

Electrowinning processes

4 Electrowinning processes

During oxidation-reduction chemical reactions there is a transfer of electrons between

substances, so we can say that there is a link between chemical processes and electrical processes that are simultaneously taking place. The impact of an external electric field causes chemical changes in a range of substances. This process is called electrolysis. By electrolysis it is possible to induce such responses, which would not take place on their own. For example, the electrolytic precipitation of metals from the salt solutions or melts. The advantage of such electrolysis is the metal (or alloy) with a high purity, which is, however, paid for by a high demands on electricity consumption. Yet, this process is used both in the production of metal from ore infusions, melted salts, and from metallurgical semi-products or waste, as well as in refining metals from both the aqueous solutions and from melts.

4.1 Definition of electrolysis Electrolysis is the process of oxidation and the reduction (redox reaction) of substances on

electrodes, caused by an electrochemical reaction by passing a DC current through an electrolyte.

In contrast, if the chemical reaction takes place spontaneously, it is possible to use it to produce

electricity. Upon this principle mobile sources of power are based, such as the batteries and accumulators.

Electrochemical reactions are carried out primarily in the electrodes submerged in the electrolyte. On a negative electrode - cathode only a reduction of ions takes place (the cathode is a donor of electrons), which become electrically neutral and settle down as atoms in a lattice on this electrode. On a positive electrode - anode only oxidation takes place, the ions of electrons get lost, and they are accepted by the anode and forwarded to the outer circle.

As an example, here is the redox reaction: Zn(s) + Cu2+ (aq) = Zn2+ (aq) + Cu(s) spontaneous reaction (ΔG° = -212 kJ.mol-1) which we can leave to take place in a Daniell galvanic cell. As the current passes through this cell, on the zinc electrode there is oxidation taking place and on the copper electrode the reduction process:

Study time: 2 hours


• define the aim of electrowinning process; • describe základní princip hydrometalrugie • list typy rozpouštědel • explain základní hydrometalurgické pochody • define rozdíly ve zpracování v různých typech loužení

Lecture

Terms: electrolyte = electrolyte solution, in which the reacting substances dissociate into ions (solutions

of alkalis, acids, or salts, molten salt bath) electrode = conductor electrodes immersed in an electrolyte conductors = enable the connection of electrodes and an external source of power


oxidation Zn(s) = Zn2+ (aq) + 2e– reduction 2e– + Cu2+ (aq) = Cu(s) Cations in the crystal lattice of the metal electrodes make an effort to pass into the solution, in

which it is immersed. The solution is, however, "preventing" the acceptance of cations and the result of these two events is equilibrium, in which the interface metal-solution creates an electrode potential. Electric potential alone is not to be measured. However, it is possible to measure the difference of potentials on two different electrodes. If we apply one electrode as the base - the standard hydrogen electrode (a platinum electrode covered with a platinum sponge immersed at 25 °C in a solution of unit activity of oxonium ions – pH=0 and hydrogen is added to it with a standard pressure of 101.3 kPa), then the potentials of electrodes measured against this electrode are called the standard redox (electrode) potentials E. Potentials E are tabulated and we can use them to build so-called electrochemical series of metal voltage, which refers to the reduction properties of metals and allows you to calculate the voltage of an electrochemical cell built from the selected electrodes. General information on the influence of reaction components concentration on the oxidation-reaction potential for any redox pair

ox + n e- ⇔ red is provided by the Nernst equation:

ox

red

aa

nFRTEE log0 −=

where E - is electrode potential corresponding to the ion concentration in the solution (V),

E 0 - standard electrode potential (v), R - universal gas constant (8,314 kJ/ (kmol. (k) ), n - the number of exchanged electrons F-Faraday constant (96485 C/mol) a - activity of oxidised or reduced forms T - temperature (K)

If E0 of this system is known (e.g. , from an electrochemical series of voltage), it is possible to use the Nernst equation to calculate the redox potential for any concentration. For two redox pairs it is then possible to predict the resulting voltage for any concentration ratios.

If we immerse two electrodes in an aqueous electrolyte solution (Figure 4.1 ) and we apply a sufficiently large external voltage to them, there will be an electrochemical reaction, i.e. electrolysis. During electrolysis the inverted progress of the redox response is enforced by the delivery of electricity , which would unintentionally take place during the release of electrical energy, in the galvanic cell. This phenomenon is used for the electrolytic production of metals from solutions (such as Cu, Ni, etc. ) from the salt melts (e.g. , alkali metals, magnesium, aluminium), the electrolytic cleaning of metals (the refining of crude copper), galvanization (chromium plating, silver plating, gold plating, coppering) in order to provide anti-corrosion protection, for anodic oxidation (electrolytic oxidation of aluminium) to create a protective oxide coating on objects of aluminium and its alloys, for the production of chlorine, sodium hydroxide, and hydrogen gas through the electrolysis of brine, etc.

Fig. 4.1 Schema of electrolysis process


Definition:

Standard electrode potentials characterize the reduction or oxidation ability of particles in aqueous solutions. The more negative the standard potential, the stronger the reducing agent. The standard electrode potential of a hydrogen electrode is agreed to be zero. A hydrogen electrode is able to measure the activity of H+ ions, thus pH. It is used as the primary standard for the measurement of pH. Hydrogen electrode Electrode process: Electrode potentia: Metallic electrode: Electrode process: Electrode potential: Metals with a negative standard potential (Tab. 1.3 ) are called unprecious metals and metals with a positive standard potential are called noble metals. Below you can see the Beket electrochemical series of elements voltage, which gives an overview of the selected metals position in relation with the hydrogen electrode: Beketov serie of elements potentials - reduced Non-noble metals Noble metals Li Rb K Cs Ba Sr Ca Na Mg Be Al Mn Ti Zn Cr Fe Cd In Tl Co Ni Sn Pb H Bi CCuu OOss RRuu AAgg HHgg PPtt AAuu (electropositive) (electronegative) Metals, which are standing on the left in an electrochemical series of voltage (alkaline and alkaline earth metals) are particularly strong reducing agents and they are easily oxidizable, any metal standing on the left is able to reduce metal (in a positive oxidized state) standing on the right and it oxidized on its own. A metal standing on the left in front of H is able to reduce (from acids) hydrogen (in a positive ox. state) and it oxidizes on its own. Metals that are very far before H will reduce it even from water. A metal (in a positive ox. state) standing on the right is able to oxidise the metal standing on the left black and reduce itself. A metal (in a positive ox. state) standing on the right behind hydrogen is able to oxidise it and reduce itself.

Fig.4.2 Electrolysis in hydrogen processing: electricity crossing through the water with solved salt, the hydrogen and oxygen are collected in container. Process is irreversible.

)()( sMeenaqMen ⇔+ −+

[ ]++≈−=+

200 lnln2

MenFRTE

aa

nFRTEE Me

Me

MeMeMe

)(2)(2 2 gHeaqH ⇔+ −+

( ) +

+

=−= HH

H aF

RTaa

FRTEE log303,2ln2 2

0 2


Table 4.1 Standard electrode potentials at 25°C (row of potentials) ( http://sk.wikipedia.org/wiki/)

Cathode Elecrode potential E°

(V) Feature Reactivity

Li+(aq) + e‐ → Li(s) ‐3,04

Rb+ + e‐ → Rb (s) ‐2,98

K+(aq) + e‐ → K(s) ‐2,93

Cs+(aq) + e‐ → Cs(s) ‐2,92

Ba2+(aq) + 2e‐ → Ba(s) ‐2,91

Sr2+(aq) + 2e‐ → Sr(s) ‐2,89

Ca2+(aq) + 2e‐ → Ca(s) ‐2,76

Na+(aq) + e‐ → Na(s) ‐2,71

Mg2+(aq) + 2e‐ → Mg(s) ‐2,38

Metals react With water

intensively and produce hydrogen

Al3+(aq) + 3e‐ → Al(s) ‐1,66

Mn2+(aq) + 2e‐ → Mn(s) ‐1,19

2H2O(l) + 2e‐ → H2(g) + 2OH

‐(aq) ‐0,83

Zn2+(aq) + 2e‐ → Zn(s) ‐0,76

Cr3+(aq) + 3e‐ → Cr(s) ‐0,74

Fe2+(aq) + 2e‐ → Fe(s) ‐0,41

Cd2+(aq) + 2e‐ → Cd(s) ‐0,40

Co2+(aq) + 2e‐ → Co(s) ‐0,28

Ni2+(aq) + 2e‐ → Ni(s) ‐0,23

Sn2+(aq) + 2e‐ → Sn(s) ‐0,14

Pb2+(aq) + 2e‐ → Pb(s) ‐0,13

Fe3+(aq) + 3e‐ → Fe(s) ‐0,04

Non

‐nob

le m

etals

Ion H+ (H3O+) concentration in

water is insufficient for reacting with

metal, increasing H+ concentration is

needed. Acides are applied, stroger acide is, intensive

reaction is produced.

2H+(aq) + 2e‐ → H2(g) 0,00 reference electrode

Sn4+(aq) + 2e‐ → Sn2+(aq) 0,15

Cu2+(aq) + 2e‐ → Cu+(aq) 0,16

Cu2+(aq) + 2e‐ → Cu(s) 0,34

Cu+(aq) + e‐ → Cu(s) 0,52

Fe3+(aq) + e‐ → Fe2+(aq) 0,77

Ag+(aq) + e‐ → Ag(s) 0,80

Hg2+(aq) + 2e‐ → Hg(l) 0,85

2Hg2+(aq) + 2e‐ → Hg22+(aq) 0,90

Au3+(aq) + 3 e‐ → Au (s) 1,37

Ce4+(aq) + e‐ → Ce3+(aq) 1,44

Au+(aq)+ e‐ → Au (s) 1,68

Co3+(aq) + e‐ → Co2+(aq) 1,82

Nob

le m

etals

Difficult or none reaction with water

and acides

http://sk.wikipedia.org/wiki/


4.2 Faraday’ laws of electrolysis The first Faraday’s law expresses that the m quantity of electrolytically excluded substances

from an aqueous solution or melted salts is directly proportional to electrochemical equivalent q, electric current I (A) passing through the electrolyte per unit of time t (s):

m = q ⋅ I⋅ t (g) Electrochemical equivalent q represents the quantity of substance excluded by electric flow 1 C .

According to the second Faraday law it applies that if the same amount of electricity passes through several different conductive solutions, the quantities of substances transformed on electrodes are in the same proportion as their electrochemical equivalents.

tIFz

Mm ⋅⋅⋅

= (g)

where M is the relative atomic weight of the excluded metal, z is the ionic charge, F is the Faraday charge of 1 moll electrons, 1F = NA . e- = 6.022.1023.1.602.10-19 = 96,487 C.

Faraday´s law has no exceptions, but in practice deviations from this law may be caused by a number of reasons, which will affect the current efficiency of the electrolysis. Most often we refer to cathodic current efficiency η It is the ratio of actually excluded metal to the theoretically possible amount:

100⋅⋅⋅

=tIq

mη (%)

among the factors that affect the precipitation of metals belong: • the type of electrolyte • the presence of colloid substances in an electrolyte • electrolyte concentration • current density

4.3 Electrolysis of aqueous solution This process is used for reduction electrolysis from leachate. An electrolyte must be well

cleaned before electrolysis (see cleaning of liquor), in which case the high purity of an excluded metal can be achieved. As an example we can use exclusion of Zn from the ZnSO solution 4 . when an insoluble anode is from lead and the cathode from aluminium. This process can be expressed by the equation:

ZnSO4 + H2O = Zn + H2SO4 + 1/2 O2 Anode reaction: 2 OH

- - 2e = H2O + 1/2 O2

Pb – 2e = Pb2+

Cathode reaction: Zn

2+ + 2 e = Zn

2 H+ + 2 e = H2

4.4 Electrolysis of melted salts bath Metals with exclusionary potential E more negative than is the potential of hydrogen E(H2/H

+)

cannot be theoretically excluded from aqueous solutions, because hydrogen will be excludes preferentially (acidic solutions with pH=0). If we increase pH (pH =10) then the potential E (H 2/H

+)

shifts by 0.6 V to negative values. For precipitation of metals with negative E the over-voltage of hydrogen is crucial, up to a certain size of E these metals can be excluded from acidic solutions (Zn/Zn2+ = - 0.763 and Mn/Mn3+

= - 1.05).


Many metals (alkali metals, alkaline earth metals) have a very negative potential E, so that, despite the above mentioned potential options, it cannot be excluded from aqueous solutions. For example it is aluminium, whose production through electrolysis will be described further on. These metals are produced through the electrolysis of melted salts.

Problems with the electrolysis of melts

Voltage losses in power supplies calls for higher effective voltage and this leads to higher energy consumption. Multi component electrolytes require high temperature T m > T el- precipitation of metal crystals T m < T el- molten metal may dissolve in the electrolyte, which leads to a loss of metal and higher

electricity consumption The anodic effect is an unfavourable side effect, it means a sudden increase of voltage on the

electrolyzer An electrolyte in aluminium production is formed by cryolite Na 3 AlF 6 and Al oxide 2 O 3

with added fluorides and chlorides to adjust the physical properties. Anodes are blocks of graphite (C) and the cathode is made of a steel tank with a graphite lining, at the bottom the aluminium is precipitated (Fig. 4.3 ).

Anode reaction: 2AlO33- - 6e

- = Al2O3 + 3/2 O2

Cathode reaction: Al3+ +3e- = Al

Fig. 4.3 Schema of electrowinning device

4.5 Electrorefining If different ions are present in the electrolyte , the first ions to be precipitated are to be the ones

with a higher potential. In refining, which means separating ions of admixture from the base metal and increasing its purity, the selective ion division is carried out. If these ions have potential E close to its size, then there is a very real danger that they will be precipitated jointly. Refined metal is classified as the anode, which is dissolved, and on the cathode, which is formed by a pure basic metal, the refined metal is excluded (reduction of ion Me 2 + ). Depending on the size of excluded E potentials the impurities are divided: in the electrolyte the less noble ingredients remain with more negative E, and into the anodic sludge the more noble impurities are transferred with more positive E.


As an example we can mention the refining of copper, where the solution CuSO 4 ,, and the anode is fire refined copper and the cathode is represented by sheets of electrolytic copper

Anode reaction: Cu – 2e = Cu2+

Cathode reaction: Cu

2+ + 2e = Cu

Under the electrode potential it is possible to divide admixture elements in anode copper into: 1. Electrically more positive - Au, Ag, Pt - do not produce ions and settle down on the bottom of electrolyzer as sludge. 2. Electrically more negative - Zn, Ni, Fe etc. - are moving into the solution, and on the cathode they

get from the electrolyte, so their concentration in the electrolyte must be checked, Pb and Sn are leaving the solution in the form of insoluble PbSO 4 and Sn(OH)4.

3. The standard potential of elements is close to the potential of copper - As, Sb, Bi. 4. Electrochemically neutral admixtures - they create compounds with copper: Cu2O, Cu2S, Cu2Se, Cu2Te.

Problems in refining electrolysis:

If electrolyte concentration reaches a critical level of ingredients, it is necessary to replace it. On the anode an insoluble layer may arise, which will increase voltage and power consumption.

Fig. 4.4 Schema of electrorefining process

Summary of terms

Elektrodový potenciál, elektrolyt, anodový efekt, katodová účinnost, Faradayovy zákony, redoxní děj, rafinační elektrolýza, elektrolýza roztavených solí.



1. Vysvětlete princip elektrolýzy. 2. Jaká reakce probíhá na katodě? 3. Co je to anodový efekt? 4. Proč některé kovy nejdou vyloučit z vodných roztoků? 5. Jaké jsou rozdíly mezi elektrolýzou z vodných roztoku a z roztavených solí?



527-28792-2. [2] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [3] Gupta Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.



Elsevier Ltd., 472 s. ISBN: 978-0-08-096789-9 [6] ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys Edited by J.R. Davis, ASM International, 2000,

s. 362-370. ISBN: 0-87170-685-7 [7] Handbook of Aluminium. Volume 1. Physical Metallurgy and Processes. Ed. by TOTEN, E.G., Mc

KENZIE, D.S. New York, 2003, 1296 s. ISBN: 0-8247-0494-0 [8] Friedrich, H. E., Mordike B.L. Magnesium Technology. Metallurgy, Design Data, Applications. Springer-

Verlag Berlin Heidelberg, 2006. ISBN-10 3-540-20599-3 [9] DRÁPALA, J. and KUCHAŘ, L. Metallurgy of Pure Metals. Cambridge International Science Publishing

Ltd., 2008.

Preparing pure metals

5 Preparing pure metals

A raw metal that has been prepared by a pyrometallurgical or hydrometallurgical process, is

mostly inappropriate for further use. Indeed, it contains impurities, which are either reduced together with it during its production, or different gases and inclusions, which got into it during production. Refining is a process of removing impurities on the basis of different chemical, electrochemical, and physical properties. The process can be carried out at elevated temperatures, it can use different tensions of vapours and gases, or chemical refining agents.

5.1 Chemical refining processes It takes place during the melting of metals with added reagents on the basis of different

thermodynamic characteristics and the following takes place: oxidation (with the following deoxidization), chlorination, sulphidation; removal of impurities, which have a higher affinity for oxygen, chlorine or sulphur than the base

metal.

An example of this can be the removal of Cu from the lead using sulphur, the dezincification of lead using chlorine after Parkes process, Harris process of As, Sb and Sn from lead.

5.2 Physical refining processes These processes use different tensions of vapour and partial pressures of gases (distillation,

sublimation, vacuum metallurgy), or the different mutual solubility of metals in liquid and solid form (liquation, segregation refining, directional crystallization, zone melting).

The process of vacuum metallurgy is based on different boiling temperatures of the base metal and ingredients or impurities, which are to be removed from the metal. In a vacuum it may be carried out as metal production, their refining, degassing and deoxidization.

Refining based on the different solubility of ingredients in a solid and liquid state - refining by liquation - precipitation melting - directional solidification (crystallization) - zone melting

A basic material parameter that is the distribution rate of admixtures and impurities in crystallization processes, is an equilibrium distribution coefficient k0, which is defined as the isothermic ratio of concentration X of the admixture element B in a solid (S) and liquid phase (L) of the basic substance:

Study time: 2 hours


1. define refining process 2. describe refining methodes 3. explain basic differences of methods

Lecture


LB

SB

XXk =0

Directional solidification

A melted ingot of refined material with a length l 0 and the initial concentration of admixtures C 0 slowly shifts the phase interface of crystal-meltage (S/L). At the same time in the solidifying interface the reallocation of admixture and impurities occurs in the basic substance.

Fig. 5.1 Schema of directional solidification Depending on the size of k0, (greater than 1, less than 1 ) it is possible to record concentration profiles after passing (passageways) of the directional crystallization: Fig. 5.2 Concentration profiles of directional crystallization a) after one pass of melting for different k0 and b) for four passes of directional crystallization with k0 = 0.1

Zone melting

With zone melting process an ingot of a length l0 is partially melted only its defined part melted, i.e. the narrow zone of a width b. The molten zone with an admixture concentrations CL, which is advancing through the ingot, has two interfaces between the meltage and solid phases: - front of melting - (x+b), where the original solid phase with concentration C 0 is melted into the zone - front of solidification - at the point (x), where the molten zone and by convection in the meltage homogenised material with a concentration CL solidifies again, but with the new concentration C 1 (x).

Fig. 5.3 Schema of zone melting


Fig.5.4 Concentration profiles of zone melting a) after one pass of zone melting for different k0 and b) after first to tenth passes of zone melting with k0 = 0.5

Summary of terms

Refining, vacuum metallurgy, zone melting, distribution coefficient, directional crystallization, concentration profile.


[1] Jak byste definovali čistotu? [2] Zopakujte si, jak se čistota označuje pomocí van Arkelova označování? [3] V čem spočívají rozdíly mezi chemickými a fyzikálními rafinačními postupy? [4] Který parametr se využívá pro rozdělování příměsí při krystalizačních procesech? [5] Čím se liší zonální tavení od směrové krystalizace?


[1] DRÁPALA, J. and KUCHAŘ, L. Metallurgy of Pure Metals. Cambridge International Science Publishing

Ltd., 2008 [2] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [3] Gupta Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.


edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5

Heavy metals

6 Heavy nonferrous metals

6.1 Main features of heavy metals Between the general or heavy non-ferrous metals we include metals, which have a density

greater than 3.5 g/cm3 to about 12 g/cm 3 and melting temperatures do not exceed the melting temperature of iron.

They can be further divided into two groups according to the melting temperature a) with mean melting temperature: Cu, Ni, CO, Mn b) with low-temperature of melting: Zn, Cd, Hg, Pb, bi, SN, SB, GA, in, TL

Further allocation may take into account various criteria, thus not only its density, but also e.g.

proton number, atomic weight, or toxicity (Ni, Cd, Hg,..). Between heavy metals we could include also other transition (transitive) metals (Pt, W, etc.), but in view of the specific characteristics they already meet criteria to be included in other groups of technical division (Tab. 1.1 in Chap.1 ). Furthermore, we will mention only the selected properties and applications to certain metals.

Most heavy metals are very toxic Hg, Pb, Sb, Ni, Cd, Co, some of which occur in the human body as so-called biogenic trace elements - Cu, Zn. Yet, it is necessary to consider them as a potential source of allergic reactions, if they are in contact with the human body in quantities greater than trace.

Table 3.1 Physical properties of heavy nonferrous metals

Metal Property

Cu Ni Pb Zn Hg Sn

Atomic mass (g/mol) 63.55 58.69 207.2 65.38 200.59 118.71 Density (x103 kg/m3) 8.96 8.9 11.34 7.13 13.56 7.3 Melting temperature (°C) 1085 1455 327.5 419.,6 -38 232 Boiling temperature (°C) 2835 2730 1740 906 357 2602

6.2 Copper

Properties:

• high electrical and thermal conductivity • good corrosion resistance

Study time: 2 hours


1. define vlastnosti vybraných obecných neželezných kovů (Cu, Ni, Pb); 2. describe jednotlivé technologie výroby těžkých kovů 3. list slitiny těchto kovů a jejich vlasnosti 4. explain oblasti použití těžkých kovů a jejich slitin v souvislosti s jejich

vlastnostmi

Lecture

Heavy metals

• high formability (A=50%) • good weldability, soldering

Raw meterials:

sulphidic: Cu2S – chalcosine CuFeS2 – chalcopyrite CuS – koveline

oxidic: Cu2O – cuprite CuCO3.Cu(OH)2 – malachite chlorides, arsenides, antimonides Vyrábí se z primárních surovin pyrometalurgicky i hydrometalurgicky, čistota vyrobené mědi se pohybuje od 99,9-99,98 hm. %. Nečistoty (Ag, As, Sb, Ni, Fe, Pb, Se, Te, O, S) výrazně snižují elektrickou i tepelnou vodivost, ale zvyšují tvrdost.

A. PYROMETALURGICKÁ VÝROBA 1. Roasting

CuFeS2 + 4 O2 = CuSO4 + FeSO4 do 400 °C

4 CuFeS2 + 15 O2 = 4 CuSO4 + 2 Fe2O3 + 4 SO2 při 400 až 600 °C

4 CuFeS2 + 13 O2 = 2 (CuO.Fe2O3) + 2 CuO + 8 SO2 při 700 až 800°C

FeS2 + O2 = FeS + SO2

4 FeS + 7 O2 = 2 Fe2O3 + 4 SO2 do 800 °C

6 Fe2O3 = 4 Fe3O4 + O2 nad 800 °C

2. Tavení koncentrátu na kamínek

reakcí mezi oxidy mědi a sulfidem železnatým se převádějí oxidy mědi zpět na sulfid, který přechází do kamínku, oxid železnatý přechází do strusky (viz schéma Outokumpu procesu)

2 CuO + 2 FeS2 = Cu2S + 2 FeS + SO2

Cu2O + FeS = Cu2S + FeO

uvolněný FeO se váže na SiO2 přítomný ve vsázce:

FeS2 + 5 Fe2O3 = 11 FeO + 2 SO2

FeS + 3 Fe2O3 = 7 FeO + SO2

Podle způsobu tavby rozeznáváme tři druhy tavení v šachtové peci:

- pyritové - používá se ke zpracování kusových rud, obsahující nejméně 25 % pyritu a určité množství křemene, rovnoměrně rozloženého v rudě. Zdrojem tepla je spalování pyritu na FeO a SO2. Dosahuje se odsíření více než 80 %.

- polopyritové - používá ke zpracování kusové rudy nebo briket s přidáním 4 – 12 % koksu. Pracuje se až se stoprocentním přebytkem vzduchu. Dosahuje se 40 až 80 % odsíření.

- redukční - používá ke zpracování aglomerátu. Zdrojem tepla je hoření koksu, kterého se přidává 12 – 15 %. Při tomto pochodu nastává poměrně nízké odsíření (30 až 40%).

Heavy metals

3. Besemerování měděného kamínku

Dělí se na dvě etapy:

I. Nejdříve se oxiduje sulfid železnatý na oxid, který se převádí do strusky přísadou oxidu křemičitého

2 FeS + 3 O2 = 2 FeO + 2 SO2

II. Oxidace sulfidu měďného a nastává reakce mezi oxidem a zbylým sulfidem za vzniku kovové mědi:

Cu2S + O2 = 2 Cu + SO2 2 Cu2S + 3 O2 = 2 Cu2O + 2 SO2 souhrnná rovnice Cu2S + 2 Cu2O = 6 Cu + SO2 Konvertorová měď se nazývá surová nebo blistr. Fig. 6.1 Outokumpu proces of smelting of Cu 4. Rafinace mědi

a) žárová rafinace:

- odstranění prvků s vyšší afinitou ke kyslíku než Cu – dmýchání vzduchu - následná dezoxidace:

- polování na husto – odstranění SO2

- polování na kujnost – redukce oxidů Cu zplodinami suché destilace

b) elektrolytická rafinace: U= 0,2-0,4V, A=2,2A.dm-2, η = 90%

- výroba Cu vyšší čistoty – elektrovodná Cu, pro vakuovou techniku - odstranění drahých kovů a stopových prvků (Se, Te, ev.Bi)

anoda: Cu0 – 2e = Cu2+ katoda: Cu2+ + 2e = Cu0

elektrolyt: okyselený roztok CuSO4, T= 50-60°C chování příměsí: E+ (Au, Ag, Pt, Se, Te, Bi) - nerozpouštějí se a přecházejí do kalů

E- (Zn, Fe, Ni, Co, Mn, As) - rozpouštějí se do elektrolytu nebo zůstávají jako

Heavy metals

B. HYDROMETALURGICKÁ VÝROBA - zpracování i chudých rud (oxidické) - použití H2SO4, rozt. Fe solí, NH4OH - výhoda, že většina příměsí tvoří málo rozpustné sírany

Loužení:

Cu2O + H2SO4 = CuSO4 + Cu + H2O Cu + Fe2(SO4)3 = CuSO4 + 2 FeSO4 Cu2S + Fe2(SO4)3 = CuS + CuSO4 + 2 FeSO4

Získávání Cu z roztoku: cementace : CuSO4 + Fe = Cu + FeSO4 elektrolýza : U= 2-2,5V, 0,5-1,2 A.dm-2,T = 35-45°C, η = 65- 90%

Čistota vyrobené mědi: 99,9-99,98 hm. % - nečistoty: Ag, As, Sb, Ni, Fe, Pb, Se, Te, O, S - výrazně snižují elektrickou i tepelnou vodivost

- zvyšují tvrdost dezoxidační prvky: Si, Zn, Sn, Al a P (avšak jejich přídavek může ve zbytkovém množství snižovat vodivost) Li, Ca borid Rozdělení slitin mědi :

1) mědi a slitiny s vysokým obsahem mědi 2) mosazi Cu-Zn 3) bronzy Cu-Sn 4) slitiny Cu-Ni

ad1) Čistá měď kov s více než 99,3 % mědi a není legován, měď je často odlévána s řízeným obsahem kyslíku (např.

0,04 %) Použití: - elektrotechnický průmysl - součásti manometrů, spínače

- tepelná technika – chladiče, výměníky - strojírenství – pružiny, ložisková pouzdra

Slitiny Cu-Be „beryliová měď “ Tvařitelná vysokopevnostní : 1,6-2,0 % Be (+ Ni, Co, Fe, Al, Si do 1,0 %) , Rm v tahu až 1479 MPa

a Rp0,2 =1344 MPa „vysokovodivostní“ slitiny : 0,2-0,7 % Be (+ Co, Ni, Fe do 2,8 %) středně vysoká elektrická

vodivost (min. 45 % IACS). Vlastnosti: dobrá až výborná odolnost proti korozi, výborná obrobitelnost za tepla, dobrá tvářitelnost

za tepla, dobrá odolnost proti otěru. Použití: vysokopevnostní - pružící vlnovce, Bourdonovy manometry, membrány, přítlačné pružiny

pojistek, pružné podložky, pojistky, pružiny, součásti spínačů, upínací kolíky, ventily, vybavení pro svařovací techniku. C17200 a C17300 je využívána zejména pro své nejiskřivé vlastnosti -bezpečnostní nástroje. vysokovodivostní - pružiny pojistek, pojistky, pružiny, elektrické vodiče, části spínačů a relé,

vybavení pro svařovací techniku, kokily pro plastové součásti, pouzdra, ventily, součásti čerpadel, převodová kola, součásti pro počítače, pro přenos dat a telekomunikace

Heavy metals

ad 2) Mosazi Cu-Zn (tombaky – nad 80%Cu) - obsah Zn od 5 – 44 % a) binární (Cu-Zn) b) legované: Pb (do 3 % zlepšuje obrobitelnost a tvářitelnost za tepla.

Al (korozivzdornost), Si (zatékavost pájek), Mn (otěruvzdornost), atd.

Tvářené mosazi - 3 hlavní skupiny : 1) Cu-Zn slitiny - červené a žluté mosazi 2) Cu-Zn-Pb slitiny - olověné mosazi 3) Cu-Zn-Sn slitiny - cínové mosazi - plechy, pásy, trubky, profily Odlévané mosazi - 4 hlavní skupiny : 1) Cu-Zn-Sn slitiny -červené a žluté mosazi 2) "manganové bronzy" vysokopevnostní žluté mosazi 3) olověné "manganové bronzy" olověné vysokopevnostní žluté mosazi 4) Cu-Zn-Si – křemíkové mosazi - tvarové lití: armatury, součásti čerpadel, ozubená kola Tvrdé pájky ad 3) Bronzy Cu-Me Tvářené bronzy - 4 hlavní skupiny: 1) Cu-Sn-P bronzy (fosforové) 2) Cu-Sn-Pb-P (olověné fosforové) 3) Cu-Al (hliníkové)- (do 11% Al) - těžko namáhaný ložiskový materál, součásti čerpadel, ventily,

elektrické kontakty, nejiskřivé nástroje, šnekové převody 4) Cu-Si (do 4 % Si) - pružiny a pružící součásti pro teploty do 250 °C a v agresivním prostředí

Odlévané bronzy - 3 hlavní skupiny: 1) Cu-Sn bronzy (cínové) ozubené a šnekové převody, ložiska, lodní armatury, pístní kroužky,

součásti čerpadel 2) Cu-Sn-Pb bronzy (olověné cínové)- kluzná ložiska 3) Cu-Sn-Ni bronzy (cínové niklové) pro elektrotechnický průmysl, ložiska a pouzdra, šnekové

převody, šoupátka ventilů, rotory 4) Cu-Pb bronzy (olověné)- kluzná ložiska Rozdělení cínových bronzů podle obsahu Sn: Cín v mědi způsobuje její rychlé zpevňování, takže moderní průmysl zpracovává tvářením cínové bronzy pouze do 8%, ostatní se používají v litém stavu, vysoký obsah cínu již způsobuje vysoké zpevnění, ale zároveň křehkost slitiny vlivem vylučování sekundárních fází (intermetalických sloučenin). Podle mechanických vlastností rozdělujeme: 1) do 8 % Sn – tvořeny jen tuhým roztokem, jsou tvářitelné za studena

Použití: plechy, dráty, aj. 2) 8-12 % Sn – vylučují se precipitáty, proto převážně v litém stavu, korozivzdorné, snesou vysoké

namáhání, Použití: strojní části, ložiska, armatury 3) 12-20 % Sn – vylučují se precipitáty nebo eutektoidní struktura, pouze v litém stavu pro ložiska 4) 20-25 % Sn – tvrdá a křehká slitina, eutektoidní struktura – používá se pouze v litém stavu, známá

je jako zvonovina

Heavy metals

ad 4) Slitiny Cu-Ni 1) konstantan – 45 % Ni Vlastnosti: vysoký elektrický odpor, velmi nízký teplotní koeficient el. odporu Použití: termočlánky 2) kupronikl – 10 - 30 % Ni + do 1,5 % Fe, zbytek Cu Vlastnosti : velmi dobré antikorozní vlastnosti, dobrá odolnost vůči napadání mořskými organismy,

dobrá pevnost a plasticita Zpracování : tváření za tepla i za studena Použití: chemický průmysl

v námořnickém průmyslu-čerpadla, ventily, chladiče v elektrárnách, zařízení pro demineralizaci, trupy lodí, výměníky tepla, chladiče • s 10 % Ni – pro lodě • s 30 % Ni – pro ponorky (vyšší tlaky)

3) niklové stříbro – 55- 65 % Cu, 10-30 % Ni, zbytek Zn Vlastnosti: bílé zbarvení, dobrá tvářitelnost, střední pevnost, velmi dobrá korozivzdornost i vůči

mořské vodě, vysoký obsah Ni brání odzinkování- nahrazuje mosazi v korozním prostředí slané vody, příznivé zabarvení (jako Ag)

Použití : plátování; ventily, armatury další součásti běžného vybavení, dekorativní a architektonické prvky

6.3 Nickel

Properties:

- M = 58.69 g/mol; ρ = 8.88 g/cm3; Tm =1445 °C; Tv = 2730 °C - mechanical strength at low and even at high temperatures - good corrosion resistance - stable in air, it oxidizes in heat - alkalic solutions resistant, low acidic solutions resistance - pozor! alergenní, mutagenní, teratogenní a karcinogenní

Suroviny: sulfidy (Ni, Fe)9S8 pentlandit NiS millerit křemičitany (Ni,Mg)6(OH)6Si4O11 garnierit (směs minerálů s obsahem Ni a Mg) arsenidy NiAs nikelin

NiAs2 chloantin Vyrábí se z primárních surovin pyrometalurgicky i hydrometalurgicky. A. PYROMETALLURGICAL PROCESSING- základní schéma:

1. Oxidační pražení - snížení obsahu S o 10 – 15 %

2. Koncentrační tavení na kamínek (Ni, Fe, Cu, S) – v pecích šachtových, plamenných, elektrických

3. Příprava jemného kamínku – odstranění Fe

- dmýcháním vzduchu oxidace železa: Fe → Fe3O4 → FeO přechází do strusky

Heavy metals

reakce mezi 3Fe3O4 + FeS + 5SiO2 = 5(2FeO.SiO2) + SO2 přechází do strusky

Fig.6.3 Fournace of concentration smelting sulfidického koncentrátu v letu kyslíkem způsob: a) finský b)

kanadský

4. Separation of Ni-Cu - Orford method – the formation of binary melting with Na2SO4 →

liquid

→ Cu → Ni

- flotation method – the use of separate crystallization Cu2S, Ni3S2 and CuNi alloys with precious metals when slow cooling:

920°C Cu2S

700°C Ni3S2 + CuNi(S) - oddělení magnetickou separací

575°C modifikace Ni3S2

magnetic portion is floated at pH 11-13

5. Processing of Ni fraction

- odlévání sulfidických anod – rafinace sulfidu:

Ni3S2 –6e = 3Ni3+ + 2S, elektrolyt Cl-, SO2-

- pražení – NiO - redukce H2 - Mondův způsob - slouží k přípravě velmi čistého niklu z jeho oxidů. Principem je

redukce oxidů vodíkem na surový kov a jeho následná reakce s oxidem uhelnatým, která poskytuje plynný tetrakarbonyl niklu. Ten se následně vede na tablety z čistého niklu, kde se při teplotě 230 °C rozloží na nikl a oxid uhelnatý, který se odvádí zpět do reakce. Proces má tři etapy:

NiO (s) + H2 (g) → Ni (s) + H2O (g) Ni (s) + 4 CO (g) → Ni(CO)4 (g) Ni(CO)4 (g) → Ni (s) + 4 CO (g)

Ni + 4CO ⇔ Ni(CO)4(g) - redukce v tekutém stavu uhlíkem s následnou rafinací

Ni3S2 + Na2S

Cu2S + Na2S

Heavy metals

6. Rafinace

- elektrolyticky (NiSO4, Na2SO4, HBO2, NaCl)

Parametry : Anoda : 1,2-2,3 A.dm-2, U=2,3-2,5V, T= 60-70°C

Fig. 6.4 Schema of electrorefining process of nickel.

B. HYDROMETALLURGICAL PROCESSES

1. Pressure leaching

equipment demands, high consumption of chemical agents, high production and quality, processing low-grade concentrates v H2SO4: T=230°C v NH3: T= 80°C + oxidace O2 contraction using H2S under pressure reduction of H2

2. Ammonia-turbid leaching

Fig.6.5

Schéma amoniakálního loužení

Heavy metals

Electrolysis: A= 3-4A.dm-2; U=4,5V; T= 90 °C; Pb anodes; electrolyt: NiSO4 + Na2SO4.

reduction roasting – metallic Ni, Co, Fe2O3

dissolving Ni, Co v rozt. NH3 + CO2 → dissolved salts Ni +1/2O2 + (NH4)2CO3 + 2NH4OH = Ni(NH3)4CO3 + 3H2O 5Ni(NH3)4CO3 + 3H2O = 2NiCO3.3Ni(OH)2 + 20NH3 + 3CO2

Použití:

– 65 % - výroba nerez ocelí – 12 % - výroba vysoce legovaných Ni slitin pro energetiku, letectví, automobilový průmysl

(turbíny, motory aj. zařízení pracující za zvýšených a vysokých teplot) – 23% -výroba jiných slitin, nabíjecích baterií, katalyzátorů a dalších chemikálií, keramiky,

mincí a odlitků, k barvení skla (na zeleno) a k pokovování (galvanické poniklování) Slitiny: TD -nikl – disperzně zpevněný Ni + 2% ThO2 (1100°C)

Slitiny

1. technický nikl – elektronické součástky, přepravní kontejnerypro ch. průmysl, součásti zařízení v potravinářském průmyslu, formy pro výrobu skleněných výrobků,…

2. Ni-Cu (monely) – odolné proti korozi, dobré pevnostní vlastnosti i za zvýšených teplot → kondenzátory, kondenzátorové plechy, destilační trubky, výparníky a tepelné výměníky, potrubí na mořskou vodu,…( Ni(65) - Cu(30) + (Si, Mn, Fe, Al) )

3. Ni-Fe-Mo-Cr – pro silně oxidační nebo redukční prostředí → námořní a petrochemický průmysl, oxidační prostředí za vysokých teplot (až 1200°C),

4. se zvláštními vlastnostmi - slitinys vysokou rezistivitou → termočlánky, topné články - chromel (Ni9-11%Cr), chromnikl (Ni-20%Cr ), nichrom (NiFeCr), konstantan (Cu-45%Ni-1%Mn), isotan (Cu-44%Ni-1%Mn), - magneticky měkké materiály – permalloy (80Ni-20Fe), supermalloy 80Ni-5Mo-zb.Fe) - s řízenou dilatací – s malou tepelnou roztažností → invar, kovar (36Ni-74Fe)

5. superslitiny- žárupevné - odolné vůči creepu princip zpevnění superslitin : precipitační vytvrzení fází γ´(Ni3(Ti,Al)) a karbidy → vysoká odolnost proti tečení (creepu) při zvýšených teplotách

Aplikace: plynové turbíny, rakety, letecké motory, chemický průmysl, metalurgické provozy, automobilový průmysl, … Tab.6.1 Mechanické a creepové vlastnosti pro vybrané superslitiny

Heavy metals

6.4 Lead Properties: vapor at T > 550°C metallic element, alloys and compounds are toxic RTG radiation absorption low thermal and electric conductivity low-temperature superconductor low hardness and strength, high ductility stable in an acidic environment (in non oxidant acids)

Suroviny:

PbS galenite PbCO3 cerussite PbSO4 anglesite

- they contain other metals (Cu, Zn, Sb, Fe, As, Bi, Sn, Au, Ag) - floation enriching to concentrate: selective: 40-75 % Pb

collective: Pb+Zn - processing secondary raw materials Processing: pouze pyrometalurgickými postupy, hydrometalurgické postupy náročné

3 možné způsoby: pražně redukční, pražně reakční - nepoužívá se, výroba olova srážením - nepoužívá se

1. Pražení a aglomerace

2. Tavení v šachtové peci – s přísadou koksu a vápence → redukce surového Pb (90-96%)

získání Pb + Ag, Au výroba chudé strusky s vysokým obsahem (vysoký obsah Pb, Zn → přepracování odkuřováním) oddělení Cu tvorbou kamínku

Reakce: PbO + CO = Pb + CO2 T=900°C PbSO4 + 4CO = 2PbO + SO2

PbS + 2PbO = 3Pb + SO2

3. Rafinace - pyrometalurgické postupy

- odměďování: a) hrubé – vycezování, využívá omezené rozpustnosti Cu v Pb b) jemné – přimíchává se elementární síra či koncentrát do roztaveného Pb, využívá vysoké afinity

Cu k S T = 350°C, Cu2S vyplouvá na hladinu - Cu (0,002%) - odstraňování Sn, As, Sb - využívá afinity ke kyslíku a) oxidace vzduchem – sběr klejtů při různých teplotách b) oxidace ledkem sodným NaNO3 – Na2O Na2O + SnO2 = Na2SnO3 - vznik čistých solí, oddělení na základě různé rozpustnosti v H2O a NaOH

Heavy metals

- odstraňování drahých kovů

Parkesování– přídavek Zn – za vzniku intermediálních sloučenin se Zn s ↑Tm a ↓ρ + omezená rozpustnost těchto sloučenin v Pb → stěry

- odstranění Bi a) do 1%Bi Krollův postup - tvorba sloučenin Bi s kovy II.sk. (Ca, Mg)- (↑Tm, ↓ρ)

b) při ↑%Bi – elektrolyticky v roztoku H2SiF6 + PbSiF6 Zpracování pochodem ISP:

do hermeticky uzavřené šachtové pece typu ISP se přidává vsázka (aglomerát s obsahem pod 1 % S a koks předehřátý na 800 °C), na ni se dmýchá vzduch předehřátý na 600-800 °C spalováním vznikají plyny obsahující i páry Zn, které odcházejí do kondenzátoru → Zn

zkondenzuje pomocí Pb rozstřikovaného míchadly Pb + zkondenzovaný Zn je odvedeno žlaby ochlazovanými vodou do rozdělovací vany → s ↓T → ↓ rozpustnost Zn v Pb vyloučená vrstva Zn se nepřetržitě odvádí k rafinaci Pb se odvádí zpětně do kondenzátoru plyny z kondenzátoru - 450 °C, obsahují až 5 % Zn → čistí se na skrubrech → Zn se oddělí v

podobě mokrého prachu (čistý plyn slouží k předehřívání vsázky a vzduchu) Pb obsažené ve vsázce se vyredukuje (spolu s Cu a ušlechtilými kovy) a vytéká z nístěje pece

spolu se struskou do předpecí → struska se oddělí a následovně zpracovává Použití Slitiny - všechny toxické!! stavebnictví : použití olova pro rozvodné trubky ve stavebnictví a pro výrobu elektrických kabelů se

nahrazuje plastickými hmotami. obaly a ochranné povlaky: hliník, cín, železo a plastické hmoty postupně vytlačují olovo z oblasti

balení a ochranných úprav výrobků. tvrdé olovo: Pb-6-7%Sb

- akumulátorové baterie (auta), chemický průmysl–odolnost proti H2SO4 - vykládání van a zařízení, pláště zemních kabelů

pájky: Pb-Sn (Cd, Ag, Cu) – s nízkou teplotou tavení (Tm) Sn: 4 - 90% podle účelu – radiotechnika, potravinářství ložiskové kovy: Pb-Sn-Sb (Cu, Ni) - babbity

- dobrá pevnost v tlaku, kluzné vlastnosti, dobrá tepelná vodivost, nízká teplota tavení, rovnoměrné rozložení složek

liteřina: Pb-Sb-Sn (dnes vlivem elektronické sazby knih na ústupu) - výroba písmen v tiskařství (↓Tm, měkká ale přitom odolává tlaku při tisku, slévatelnost)

Pb - jako přísada v jiných slitinách – zlepšení technologických vlastností (mosazi, automatové oceli, Pb- bronzy, ...) Sloučeniny všechny toxické!! - účinně nahrazovány jinými látkami Pb3O4 – ochranné nátěrové hmoty PbCO3 – krycí běloba (C2H5)4Pb – tetraetylolovo - antidetonační přísada do benzínů - dnes zakázána a nahrazována přísadami aromatických uhlovodíků

Heavy metals

Summary of terms

Blistr, měděný kamínek, bronzy, mosazi, dělení Ni-Cu kamínku, Mondův proces, techologie ISP, vycezování, stěry.


1. Jaké znáte suroviny pro výrobu mědi? 2. Popište pyrometalurgický způsob výroby mědi. 3. Jak je možné rafinovat měď? 4. Které bronzy znáte? 5. Vysvětlete princip Mondova způsobu zpracování niklového podílu. 6. Co je principem hydrometalurgické výroby niklu? 7. Které slitiny niklu znáte? 8. Co jsou to superslitiny a jaké vlastnosti mají? 9. Vysvětlete pyrometalurgický způsob výroby olova. 10. Jaký je princip techniloige ISP? 11. Co je to parkesování? 12. Jak se odstraňuje Bi z olova? 13. Jaké nežádoucí vlastnosti má olovo?


[1] HABASHI, FATHI. HANDBOOK OF EXTRACTIVE METALLURGY, VOL. 2-4. WEINHEIM: WILEY-

VCH, C1997, ISBN 3-527-28792-2. [2] www.Webelements.com [3] http://www.madehow.com/Volume-4/Tin.html [4] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5 [5] Schlesinger, M E., King, M. J., Sole, K.C., Davenport, W.G. Extractive Metallurgy of Copper, 2011,

Elsevier Ltd., 472 s. ISBN: 978-0-08-096789-9 [6] Gupta, Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.

KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6 [7] http://en.wikipedia.org/wiki/Zinc_smelting [5] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [6] ASM Specialty Handbook: Nickel, Cobalt, and Their Alloys Edited by J.R. Davis, ASM International, 2000,

s. 362-370. ISBN: 0-87170-685-7

http://www.webelements.com/

http://www.madehow.com/Volume-4/Tin.html

Noble metals

7 Noble metals

7.1 Main features of precious metals Among noble metals belong those, which are very resistant against the corrosive action of the

surrounding environment and oxidation in the air. From the chemical point of view it can be characterized as electrically positive (see the Beket series of elements voltage), and that is why we could also include copper, mercury or bismuth, which we have already assigned to the group of heavy metals. According to the melting temperature we can further divide them into:

a) with medial melting temperature: Ag, Au b) with high temperature of melting: Ru, Rh, Pd, Os, Ir, Pt

Table7.1 Physical properties of selected noble metals

Metal Property

Au Ag Pt Pd

Atomic mass (g/mol) 196,97 107,87 195,08 106,4 Density (x103 kg/m3) 19,28 10,49 21,45 12,02 Melting temperature (°C) 1063,7 960,5 1769 1555 Boiling temperature (°C) 2530 2212 3827 2927

7.2 Gold Properties:

měkké, houževnaté (pevnost ses dá zvýšit přidáním jiných kovů) tvárné: z 1 g Au→ 1 m2 fólie výborný tepelný a elektrický vodič dobré slévarenské vlastnosti chemicky a korozně velmi odolné → reaguje pouze s lučavkou královskou, se směsí

organických sloučenin (jodu, tetraetylamoniumjodidu a acetonitrilu) a s vodným roztokem jodidu draselného a jodu

čistota: ‰, karát=1000/24 ‰ ; 1 unce [oz] = 28,3495 g ; tradiční jednotka hmotnosti zlata : 1 trojská unce [Troy oz] = 31,1034807 gramů (→ 32,15

trojských uncí = 1 kg ) Suroviny a výskyt:

- poměrně vzácné → v zemské kůře v obsahu 4 – 5 μg/kg - ryzí forma (24 karátů) nebo jako elektrum (sloučenina s Ag)

Study time: 2 hours


1. define ušlechtilé kovy a jejich vlastnosti; 2. describe technologie výroby zlata, stříbra a platinových kovů 3. vybrat metodu pro získání stříbra z výroby olova 4. určit oblasti aplikací ušlechtilých kovů

Lecture

Noble metals

- polymetalické teluridy a selenidy, křemenné žíly - doprovází sulfidické rudy (Cu, Pb, Zn, Sb)- vedlejší produkt z výroby těchto kovů - jižní Afrika, Ural, Austrálie; Kanada, Sibiř.

Výroba:

Rozdrcené rudy se zpracují 2 způsoby:

1. Amalgamace:

rozpouštění Au v Hg → vznik amalgámu filtrace a destilace → surové Au –60-85% (Ag, Cu) rafinace pomocí solí (Na2CO3, NaNO3, borax Na2B4O7.10H2O)

2. Kyanidování:

loužení v roztoku kyanidu za přítomnosti vzduchu 4Au + 8KCN + 2H2O + O2 → 4KAu(CN)2 + 4KOH

vypírání, filtrace srážení pomocí Zn

2KAu(CN)2 + 2Zn + KCN + H2O → 2K2Zn(CN)4 + 2Au + 2 KOH + H2

Afinace:

odstranění příměsí a oddělení mědi a ušlechtilých kovů kvartace (Ag:Au = 3:1) → rozpouštění v HNO3 chlórování – Cl2 → odstranění chloridů elektrolýza – dva stupně (1.Ag, Au v kalech - tavení, 2. Au)

- rozt. AuCl3 + HCl, T=55-65 °C, 1,5V, 13A/dm3 - regenerace elektrolytu - Pt H2PtCl6 + 2NH4Cl = (NH4)2Pt + 2HCl Další postupy využívají: sorbce na aktivním uhlí, iontovou výměnu a extrakci – loužení v HCl + Cl2 a následnou extrakci v roztocích aminů Použití a slitiny:

- klenotnictví (změna barvy - slitiny s Pd, Ag, Cu, Ni, Pt ) - dekorace skla a porcelánu - součásti laboratorních přístrojů - trysky na výrobu umělého hedvábí - hroty per Ag-Au-Cu - zubní lékařství – Pt-Au - mechanické a galvanické pokovování - elektrotechnika – kontakty - fólie v kosmickém a lékařském odvětví - investiční kov

Noble metals

Obr. 7.1 Schéma technologického postupu úpravy zlatonosné rudy (Dinter, 1996)

7.3 Silver Vlastnosti:

nejlepší elektrická vodivost ze všech kovů výborná tepelná vodivost dobře tvařitelné vysoká odrazivost pro viditelné světlo poměrně stálé i ve slabších oxidačních činidlech a rozt. solí, zřeď. H2SO4 rozpouští se v konc. silně oxidačních kyselinách HNO3 a horké H2SO4

3 Ag + 4 HNO3 → 3 AgNO3 + NO + 2 H2O

za přítomnosti kyslíku se rozpouští v roztocích alkalických kyanidů za vzniku kyanostříbrnanového iontu [Ag(CN)2]- na suchém čistém vzduchu je stříbro neomezeně stálé, stačí však i velmi nízké množství

sirovodíku H2S, aby stříbro začalo černat (vznik vrstvy Ag2S na povrchu)

http://cs.wikipedia.org/w/index.php?title=Kyanid&action=edit

Noble metals

Suroviny a výskyt: - vzácné- v zemské kůře obsah cca 0,07 – 0,1 mg/kg - obvykle jako sloučeniny AgCl, Ag2S, komplexní rudy As, Sb - doprovází sulfidické rudy (Cu, Pb, Zn, Ni, Sn) - surovina z výroby těchto kovů –

Patinsonování, Parkesování - vzácněji jako ryzí kov - Mexiko, Kanada, Peru, Austrálie a USA.

Pyrometalurgická výroba:

1. Parkesování:

- při výrobě Pb, založeno na tvorbě intermetalických sloučenin Ag, Au se Zn - ↑Tm a ↓ρ, nerozpustné

přidání Zn při 500 °C, ochlazení na 350 °C – 1. pěna - bez Ag další Zn – 2. pěna hlavní část Ag odstranění Pb - vycezováním při 600°C

- lisováním + destilace Zn - shánění – oxidace Pb (1000-1100°C)

rafinace dezoxidací a redukcí dřevěným uhlím 2. Elektrolyticky z Cu, zpracování odpadů

Obr.7.2 Schéma postupu výroby stříbra ze stříbrnatého olova parkesováním

Hydrometalurgická výroba:

1. Amalgamace: rozpouštění Ag v Hg -vznik amalgámu,

Noble metals

z AgCl nejprve rozklad (Fe, Cu) na Ag – jinak ztráty HgCl filtrace a destilace

2. Kyanidování:

loužení v roztoku kyanidu za přítomnosti vzduchu 4 Ag + 8 KCN + 2 H2O + O2 = 4 KAg(CN)2 + 4 KOH

AgCl + 2 KCN = KAg(CN)2 + KCl - nebezpečí vzniku HCN - zamezení přísadou CaO vypírání, filtrace srážení pomocí Zn 2 KAg(CN)2 + Zn = 2 K2Zn(CN)4 + 2 Ag

Rafinace

– oddělení ušlechtilých kovů elektrolýza - roztok AgNO3 + HNO3, T=55-65 °C, 3V, 2-5A/dm3

Použití, slitiny a sloučeniny:

elektrotechnika - kontaktní slitiny -Ag-Cu-Cd, W, Mo, Ag-Ni - stříbrné pájky Ag-Zn-Cu(Cd), Ag-Sn-Cu - záznamová média – vrstvy v CD a DVD (u levnějších Ag nahrazeno Al)

galvanické pokovování stolní nádobí a příbory zubní technika – stříbrné amalgámy Ag-Sn-Hg, slitiny Pd-Ag, Au-Ag kvalitní zrcadla katalyzátory v organochemických reakcích spotřební průmysl - antibakteriální úpravy domácích spotřebičů pomocí nanočástic Ag klenotnictví- slitiny Au-Ag, Ag-Cu, pokovování rhodiem sloučeniny využívané v průmyslu: AgNO3, AgCl a AgBr (fotografický průmysl), AgI

Obr.7.3 Výroba stříbra v letech 2002-2006 podle států

Noble metals

7.4 Platinum and platinum metals group

Vlastnosti Pt:

ušlechtilý, odolný, kujný a tažný kov, elektricky i tepelně středně dobře vodivý snadno se rozpouští v lučavce královské, pomalu se rozpouští i v HCl za přítomnosti vzdušného kyslíku nebo peroxidu vodíku. společně s Os a Ir patří k prvkům s největší známou hustotou (Pt – 3x větší hustotu než Fe) pohlcuje značné objemy plynného H2 katalytické vlastnosti a to jak ve sloučeninách, tak ve formě kovu výjimečná chemická stálost těžkotavitelný elektricky vodivý

Suroviny a výskyt:

Jižní Afrika, Sibiř, Ural, Kanada, USA prakticky pouze ve formě ryzího kovu (téměř vždy jsou v menší míře přítomny i další Pt kovy-

Rh, Pd, Ir) uvnitř ultrabazických magmatitů zastoupení v zemské kůře velmi malé, průměrný výskyt činí 0,005-0,01 ppm (mg/kg). hromadí v říčních i mořských píscích - rýžování. sekundární suroviny (recyklace)- elektroodpad, kovový šrot, chemické roztoky, kal, různé filtry,

žáruvzdorné pecní vyzdívky, opotřebované autokatalyzátory, ostatní katalyzátory a jiné výrobky.

PtAs Sperylit 52 – 56 % Pt PtAs Cooperit 80 – 83 % Pt RuS Laurit Fe/Pt Feroplatina 10 % Fe/75 % Pt Os/Ir Osmiridium Pt Polyxen

Výroba:

Výroba Pt a separace Pt kovů – 2 postupy založené na: Pt, Pd, Au - rozpustné v kyselinách Ru, Rh, Ir a Os - v kyselinách nerozpustné

Použití a slitiny:

legura do slitin s Rh a Ir pro tavící a spalovací kelímky a vysokoteplotní zařízení materiál do speciálních pecí na tažení optických vláken ve sklářském průmyslu katalyzátor v chemickém průmyslu při organických syntézách autokatalyzátory cis-Pt ve velmi účinná cytostatikách elektrické kontakty Pt-Rh termočlánky pro sklářství a metalurgii Šperky pokovování méně ušlechtilých kovů součástí některých dentálních slitin především ve spojení s moderními keramickými materiály

Noble metals

Platinové kovy se vyskytují v různém množství spolu s Pt. Následující schéma znázorňuje získávání jednotlivých ušlechtilých kovů (Obr.7.3).

Obr.7.4 Zpracování surové platiny

pro výrobu dalších ušlechtilých kovů

Summary of terms

Kyanidování, amalgamace, parkesování


1. Jaké základní vlastnosti mají ušlechtilé kovy? 2. Jaké technologie se využívají pro výrobu zlata a stříbra? 3. Které kovy patří do skupiny platinových kovů? 4. Z jakých surovin se získávají platinové kovy? 5. Jaké použití mají ušlechtilé kovy a ve kterých oblastech? 6. Co je to parkesování? 7. Vysvětlete proces amalgamace. 8. Objasněte technologii kyanidování.

Noble metals


[1] ENGHAG, P. Encyclopedia of the Elements. Technical Data·History·Processing·Aplications, 2004,

WILEY-VCH Verlag GmbH & Co KgaA, 1243 s. ISBN 3-527-30666-8 [2] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5 [3] HABASHI, FATHI. HANDBOOK OF EXTRACTIVE METALLURGY, VOL. 2-4. WEINHEIM: WILEY-

VCH, C1997, ISBN 3-527-28792-2. [4] www.Webelements.com [5] Davis, R. METAL HANDBOOK. DESK EDITION, ASM INTERNATIONAL, 1998, 1521 S. [6] GUPTA CH. K. CHEMICAL METALLURGY: PRINCIPLES AND PRACTICE. 2003 WILEY-VCH

VERLAG GMBH & CO. KGAA, WEINHEIM, 795 S. ISBN: 3-527-30376-6


Light metals

8 Light metals

8.1 Basic characteristics of light metals Among light metals can be included metals, which have a density of 0.53-3.75 (g/cm 3 and its

melting temperature does not exceed the melting temperature of iron. they can be further divided into two groups according to their melting temperature: a) with mean melting point: Al, Mg, Be, Ca, Sr, Ba. b) with a low melting point: Li, Na, K, Rb, Cs. Further allocation may take into account physical and chemical properties of light metals: a) I. group: alkali metals - Li, Na, K, Rb, Cs, (Fr - radioactive). b) II. group: alkaline earth metals - Be, Mg, Ca, Sr, Ba.

Aluminium is placed alone - in III. group.

Structure and properties of light metals Properties of alkali metals

Table 8.1 Physical properties of alkali metals

Element Property

Lithium Sodium Kalium Rubidium Cesium

Atomic mass 6.94 22.99 39.10 85.47 132.91 Melting point Tm (°C) 180.5 97.7 63.4 39.3 28.5 Boiling point Tv (°C) 1342 883 759 688 671 Density (g/cm3) 0.53 0.97 0.86 1.53 1.88 Lattice KSC KSC KSC KSC KSC Lattice parameter (nm) 0.351 0.429 0.533 0.559 0.614 Atomic radius (nm) 0.152 0.186 0.227 0.247 0.266 Oxidizing number I I I I I Electronegativity (Pauling) 0.97 0.93 0.82 0.82 0.79

lightest from all known metals easily pass on positive monovalent ions from Li toward to Cs - metallic properties are increasing from Li toward to Cs - density is increasing (the first three are lighter then the water), but their

melting point is decreasing highly reactive, their appearance in the nature is only in the form of compounds they react vigorously or explosively with water with the hydrogen evolution

Study time: 2 hours


1. define the group of light metals 2. describe the properties of light metals 3. explain technologies of processing 4. list the alloys on the base of aluminum or magnesium 5. define the properties of aluminum or magnesium and their alloys

Lecture

Light metals

Properties of II.A group metals (Be, Mg) and alkaline earth metals

Table. 8.2 Physical properties of Be, Mg and alkaline earth metals Element

Property Beryllium Magnesium Calcium Stroncium Baryum

Atomic mass 9.01 24.31 40.08 87.63 137.33 Melting point Tm (°C) 1287 650 842 777 727 Boiling point Tv (°C) 2471 1091 1484 1382 1897 Density (g/cm3) 1.85 1.74 1.55 2.63 3.51 Lattice HTU HTU KPC KPC KSC

Lattice parameter (nm) 0.229 0.358

0.321 0.521

0.558 0.608 0.503

Atomic radius (nm) 0.112 0.160 0.197 0.215 0.215 Oxidizing number II II II II II Electronegativity (Pauling) 1.57 1.31 1.00 0.95 0.89 ability to form positive bivalent ions is growing with increasing atomic mass from Be toward to Ba metallic character, acidity, solubility and hydroxide stability is increasing from Be toward to Ba higher melting points compared to alkali metals (Be has the highest one: 1287 °C) they easily compound with halogens and at higher temperatures with nitrogen (nitrides), carbon

(carbides), and hydrogen (hydrides), etc. fast oxidizing in air with oxide layer formation all react vigorously with the water with evolution of hydrogen

Reactivity – reaction: 4 Li + O2 → 2 Li2O (Li2O2) 2 Na + O2 → Na2O2 2 Be + O2 → 2 BeO 4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2 Na2O2 + CO2 → Na2CO2 + O2 Na2O2 + CO → Na2CO3

CaCO3 → CaO + CO2

Raw materials Alkali metals

•• Li - ferro-magnesium minerals (substitution of Mg, LiAlSi2O6 - spodumen) • Na - NaCl (halite), Na2CO3.NaHCO3.2H2O (trona), NaNO3 (saltpeter), Na2B4O7.10H2O (borax),

kernite, Na2SO4 (mirabilite) • K - KCl (sylvite), KMgCl3.6H2O (carnallite), K2Mg2(SO4)3 • Rb, Cs – accompany Li, Cs4Al4Si9O26 (pollucite) • Fr – uranium and thorium minerals

Alkaline earth metals

•• Be - Be3Al2 (SiO3)6 (beryl, emarald) • Mg - MgCa(CO3)2 (dolomite), MgCO3,(magnesite), KMgCl3.6H2O, K2Mg2(SO4)3, (Mg,Fe)2SiO4 (olivine), Mg3Si2O5(OH)4 (amiant) • Ca - CaCO3 (limestone), CaF2 (fluorite), CaSO4.2H2O (gypsum), Ca5(PO4)F (apatite) • Sr - SrSO4 (celestite), SrCO3 (strontianite) • Ba - BaSO4 (barite), BaCO3 (witherite)

Light metals

Processing Alkali metals

•• Li - LiCl/KCl (55:45) fused salt electrolysis • Na - NaCl/CaCl2 (40:60) fused salt electrolysis • K - metalothermic reduction KCl + Na → K + NaCl (580°C) • Rb, Cs - metalothermic reduction RbCl (nebo CsCl) + Ca → Rb (Cs) + CaCl2

Be, Mg and alkaline earth metals

•• Be - metalothermic reduction: BeF2 + Mg → Be + MgF2, BeCl2 fused salt electrolysis • Mg - metalothermic reduction: (MgO.CaO) + FeSi → MgCa2SiO3 + Fe, MgCl2 fused salt

electrolysis • Ca - CaCl2 fused salt electrolysis • Sr, Ba - metalothermic reduction (Al), fused chloride salt electrolysis

8.2 Aluminum Physical properties: M = 26.98 g/mol ρ = 2.7.103 kg/m3 Tm = 660 °C Tv = 2270 °C

structure FCC, lattice parameter a=0.40412 nm electric resistenc 0,027-0,029 Ωmm2/m linear shrinkage 1.75%, volumetric shrinkage 6 % non magnetic

high thermal and electrical conductivity high corrosion resistence ( increasing with purity of Al, formation of Al2O3 layer ) značná afinita ke kyslíku (vznik Al2O3) low stability in strong alkalis low strength properties reduction properties

Raw materials bauxites Al2O3.3H2O hydrargilit Al2O3. H2O boehmit non-bauxites (Na, K)2O.Al2O3.2SiO2 nepheline

Production block diagram: bauxite → Al2O3 → electrolysis → refining → Al

ev. (termická redukce) ev. Al slitiny Pro výrobu hliníku elektrolýzou se musí připravit čistý oxid Al2O3 z rud. Nejčastější zpracovávanou rudou je bauxit, jehož kvalita se posuzuje nejen podle obsahu Al2O3, ale i podle obsahu SiO2. Criterium for selecting the method of production The quality of bauxite not only according to Al2O3 content, but also according to the silicon (bauxite) module:

Light metals

Silicon module: M = 2

32

.%.%

SiOwtOAlwt

It is possible to classify bauxite according to its density into :

a) M > 10 ⇒ high-quality, suitable for Bayer´s method, today the same as M > 6-7 b) 3 < M < 10 ⇒ low-grade, which is used for the sintering method c) M < 3 ⇒ unsuitable for the production of Al2O3

Production methods of Al2O3: a) alkaline (alkaline leaching) b) acidic (acidic leaching)

Alkaline production method are mostly used, possible to classify into 3 groups:

1. Bayer‘s method 2. Sintering method 3. Combined methods (Bayer‘s method + Sintering method)

Bayer’s method

- pro zpracování kvalitního bauxitu s 2-5% Al2O3 Podstata: tlakové loužení hydroxidem sodným při teplotě 110-230 °C, tlaku 0,1-3 MPa v autoklávech,

za vzniku roztoku hlinitanu sodného a nerozpustného zbytku, který se následně filtruje a hydrolyzuje

Al2O3.n H2O + 2 NaOH = 2 NaAlO2 + (n+1).H2O hlinitan sodný or Al(OH)3 + NaOH ↔ NaAlO2 + 2 H2O hlinitan sodný

Fig. 8.1 Autoclave

1- suspension input 2- suspension output 3- vapour input to heater 4- condensate output 5- stirring

Light metals

Fig.8.2 Srovnání obou zásaditých metod výroby oxidu hlinitého

Kalcinace probíhá v závislosti na teplotě v následujícím sledu: 250 °C 550 °C 1200°C

Al(OH)3 → AlOOH → γ-Al2O3 → α-Al2O3 boehmit diaspor

Spékací metoda

- pro zpracování bauxitu s vyšším obsahem SiO2 Podstata: rozemletý bauxit se spéká se sodou a vápencem za teplot 1150-1200°C za vzniku spečence

dle rovnice: Al2O3.n H2O + Na2CO3 = Na2O.Al2O3 + n. H2O

hlinitan sodný - Al2O3 zreagoval na pevný hlinitan sodný dobře rozpustný ve vodě, - louží se dále vodou za vzniku hlinitanového roztoku a nerozpustného zbytku, oxid železitý a oxid křemičitý se oddělí při loužení spečence horkou vodou ve formě nerozpustného hnědého kalu.

Elektrolýza oxidu hlinitého Elektrolytická výroba probíhá obecně podle chemických rovnic: 2 Al2O3 (elektr) + 3 C(s) → 4 Al (l) + 3 CO2(g)

Al2O3 (elektr) + 3 C(s) → 2 Al (l) + 3 CO(g)

Elektrolyt

Charakteristika elektrolytu: kryolit Na3AlF6, ve kterém je rozpuštěn Al2O3

Light metals

Přísady snižují teplotu tavení kryolitu na 920-970°C (viz bin.diagram soustavy Na3AlF6 -Al2O3) 3-10% CaO, který reaguje s kryolitem na CaF2 Al2O3, Na3AlF6, (kryolitový poměr NaF/ AlF3 )

Roztavený kryolit disociuje: Na3AlF6 → 3Na+ + AlF63−

- stupeň disociace závisí na kryolitovém poměru Hexafluorohlinitý iont se parciálně rozkládá v tavenině: AlF6

3− → AlF4− + 2F− Přídavek Al2O3 vede ke vzniku oxyfluoridových iontů: 4 AlF6

3− + Al2O3 → 3 Al2OF62− + 6F−

2 AlF63− + 2 Al2O3 → 3 Al2O2F4

2−

Fig.8.5 Schéma konstrukce elektrolyzéru Hall-Héroultova s předem vypálenými anodami Anoda: nerozpustná (grafit -C) - předem vypálená nebo samovypalovací Söderbergova reakce na anodě : C + 2O2→ CO2(g) + 4e−

Katoda:

ocelová vana s uhlíkovou vyzdívkou, na které se vylučuje (redukuje) zájmový kov:

reakce na katodě: Al3+ +3e- = Al

Anodový efekt Vzniká, existuje-li spád napětí mezi anodou a elektrolytem (vzrůst napětí na anodě). Negativní účinky: - prohřátí pece - ztráty energie

- natavení postranní garnisáže

Light metals

- snížení proudové účinnosti - emise škodlivých plynů (CF4 a C2F6)

Pozitivní účinky: - přímá indikace stavu nízké koncentrace Al2O3 - očištění povrchu anody, zejm. od uhlíkové pěny v elektrolytu

Rafinace hliníku Method of industrial refining

• ustálení (odstátí) taveniny Al • vakuová rafinace → rafinace od H, Na • probubláváním plyny→ rafinace od H, kovových nečistot (Ca, Na, Mg), inkluzí • solnými přísadami • filtrací

Special refining method • fraction crystallization → (3N6-4N) • three-layer electrorefining → (4N - 4N8) • electrolysis in organic media → (5N) • zone refining → (5N - 6N)

Fig.8.6 Schéma trojvrstvé metody rafinace Al

Elektrolytická rafinace: → čistota 4N - trojvrstvá metoda: anodické rozpouštění Al z jeho slitiny Al-25%Cu a vyloučení na katodě - teplota 760-800°C anoda: Al25Cu ( vysoká ρ = 3,2-3,5 g/cm3 → na dně vany) elektrolyt: 60% BaCl2, 19-23% AlF3, 17% NaF, 3-4% NaCl, ρ = 2,7g/cm3 katoda: grafit – ponořena v tavenině Al, ρ =2,3g/cm3

E+: Fe,Si,Mn,Cu – nerozpouštějí se → zůstávají v anodovém kovu E-: Mg,Ca, Na – rozpouštějí se, mají vyšší vylučovací potenciál → v elektrolytu

Karbotermická redukce hliníku Al2O3 + 3 C = 2 Al + 3 CO

Light metals

Karbotermická redukce je složitá, protože jsou třeba extrémně vysoké teploty kolem 2000°C a ztráty tepla jsou značné. Rovněž je tendence přednostní tvorby Al4C3 a plynného produktu CO a při přebytku Al2O3 i oxikarbidů.

2 Al2O3 + 9 C → Al4C3 + 6 CO(g) Al4C3 + Al2O3 → 6 Al(l) + 3 CO(g)

Proces: surovina na bázi jílu a bauxitů se redukuje koksem → cca 70 % Al a 30 % slitiny s Si. Výhoda:

náhrada dražší elektrické energie tepelnou energií. Nevýhoda:

při provozních teplotách - Al významný tlak par → snižuje účinnost reakce, tvoří se suboxidy přímá karbotermická redukce - ve vysoké peci (jako při výrobě Fe)

Jiný způsob redukce - v elektrické obloukové peci → tavený oxid hlinitý, odstraní se příměsi. Tavený oxid hlinitý se v další peci redukuje na čistý hliník za přítomnosti čistého uhlíku. Spotřeba energie v praxi - 9,07 kWh/kg Al je příznivá v porovnání s hodnotou 14,43 kWh/kg Al u Hall-Héroultova procesu (elektrolýza).

Fig. 8.7 Karbotermická redukce oxidu hlinitého

Příklady výrobků a použití Al : plechy, profily, tyče, pásy, trubky, dráty, výlisky nádobí, plechovky na nápoje, fólie dezoxidační přísada vinutí v transformátorech plátování hliníkem slitiny (s Si, Cu, Zn,Ti, Mg, Mn, Li)

Light metals

Rozdělení slitin hliníku

Hlavním důvodem k legování hliníku: zvýšení pevnosti, tvrdosti a odolnosti proti otěru, creepu, relaxaci napětí a únavě v praxi : slitiny hliníku = slitiny komplexní

což představuje odlišnost a komplikovanost mikrostruktury jednotlivých slitin - lze je však odvodit z několika základních binárních nebo ternárních slitin : Al-Cu, Al-Mg,Al-Mn, Al-Si, Al-Zn; Al-Cu-Mg, Al-Cu-Si, Al-Cu-Ni, Al-Cu-Zn, Al-Mg-Si, Al-Mg-Mn, Al-Zn-Mg, …

Základní rozdělení slitin: a) slitiny určené ke tváření:

za vyšších teplot - tvořeny homogenním tuhým roztokem (substituční tuhý roztok), který je pevnější a tvrdší než čistý Al; za nižších teplot - následkem změny rozpustnosti dojde k precipitaci další fáze, což znamená příspěvek ke zpevnění slitiny.

b) slitiny určené ke slévání: větší obsah přísad vede k heterogenitě a ke vzniku eutektik; s rostoucím množstvím eutektika klesá jejich tvárnost, ale roste zabíhavost; mají jen 15-20 obj.% eutektika (kromě slitin eutektických).

c) slitiny vyrobené práškovou metalurgií (SAP) struktura tvořena Al nebo Al slitinou a jemnými částicemi Al2O3 (6-22%) ; zvýšená pevnost; vysoká korozivzdornost; žárupevnost do 500 °C.

d) kompozity struktura tvořena Al nebo Al slitinou a Al2O3, SiC a j. zpevňujícími složkami (částicemi, vlákny ap.) způsoby přípravy – P/M, tlakové lití,… vlastnosti-vyšší pevnost a žárupevnost než Al a jeho slitiny

Hliník a slitiny ke tváření 1. Hliník - čistota 99,0 hm.% (A0) a vyšší (nečistoty – Si, Fe) ( A95, A999)

Vlastnosti : výborná korozivzdornost, vysoká tepelná a elektrická vodivost nízké mechanické vlastnosti, výborná tvařitelnost zvýšení pevnosti- deformačním zpevněním

Použití : chemie, elektrotechnika (vodiče vysokého napětí, vodiče elektrického proudu v domácnostech– 3x lehčí než Cu –1kg Al převede 2x více elektřiny než 1kg Cu; ALE dnes problémy se stárnutím vodičů) potravinářství – fólie, plechovky, obaly

2. Dural, Superdural ( Al-Cu, Al-Cu-Mg) (2-4,5 hm.% Cu, do 1,8 hm.% Mg)

TZ: rozpouštěcí žíhání + precipitační vytvrzení – zvýšení mechanických vlastností (meze kluzu) - vlastnosti přesahují leckdy vlastnosti nízkouhlíkových ocelí

Vlastnosti: omezená korozivzdornost, za určitých podmínek-mezikrystalická koroze – plátování čistým hliníkem, slitinami Mg-Si nebo slitinou s 1 % Zn (povlak tvoří 2,5-5% celkové tloušťky na každé straně) Rp0,2 300-350 MPa, Rm 420-450 MPa

Light metals

Použití : součásti a konstrukce vyžadující vysokou specifickou pevnost- kola nákladních aut a letadel, konstrukční součást aut, trupy letadel a pláště křídel, konstrukce a součásti požadující pevnost do 150°C

3. Al-Mn (do 1,5 hm.% Mn, příp.Mg)

TZ: slitiny se většinou jen žíhají (vytvrzení ne), zdroj zpevnění – zvýšení pevnostní úrovně základního tuhého roztoku, sekundární fáze přispívá minimálně

Vlastnosti : o 20 % vyšší pevnost než čistý hliník Použití: pro středně pevnostní požadavky ve spojení s dobrou obrobitelností

4. Al-Si (do 12 hm.% Si) TZ: nezpracovávají se Vlastnosti: nižší TM slitiny, Si nepůsobí na křehnutí, nízký koeficient tepelné roztažnosti, vysoká

otěruvzdornost , vyšší obsahy Si-tmavě šedé zbarvení Použití: pojidlo při svařování a pájení hliníkových slitin, které mají vyšší TM

architektura

5. Al-Mg, Al-Mg-Cu (do 2-7 hm.% Mg) TZ : nezpracovávají se Vlastnosti: dobrá svařitelnost, dobrá korozivzdornost v mořském prostředí, Použití: lodě, čluny, části jeřábů, pouliční svítilny, dělové lafety,..

6. Al-Si-Mg TZ: zpracovávají se, vytvrditelné, precipitáty Mg2Si Vlastnosti: dobrá tvařitelnost, svařitelnost, obrobitelnost, korozivzdornost, střední pevnost Použití: stavebnictví, mosty, zábradlí, svařované konstrukce,…

7. Al-Zn (1-8 hm.%) +Mg, Cu, Cr, Sc (malá množství) TZ: zpracovávají se

vysokopevné - nižší odolnost vůči koroznímu praskání pod napětím proto TZ mírně přestárnuté pro získání kombinace pevnosti, korozivzdornosti a lomové houževnatosti

Vlastnosti: středně až vysokopevné hliníkové slitiny Použití: letecké konstrukce, zařízení pro přepravu a zařízení s vysokou pevností při malé

hmotnosti

8. Různé : žárupevné slitiny – komplexní legování –P/M-disperzní zpevnění (Al-Fe-V-Si, Al-Fe-Ce) Al-Li- precipitační vytvrzení-nízká hustota, vysoká pevnost; letectví a kosmonautika Al-Sc – precipitační vytvrzení - letectví, rámy sportovních kol (ALE: vysoká cena Sc!)

Tepelné zpracování (TZ), tepelně mechanické zpracování: Tváření - zatepla i zastudena : válcování, protlačování, kování, tažení Výsledná struktura - závisí na celé tepelně-mechanické historii materiálu (výrobku) – pojmy : - struktura licí, deformační nebo žíhací, - sekundární fáze - mohou být fragmentovány a seřazeny do směru největšího protažení, - zrna mohou být protažena ve směru tváření (anizotropie vlastností), vznik textur, - rekrystalizace statická nebo dynamická, zotavení, atd.

Hliník a slitiny slévarenské - na bázi stejných binárních (ternárních) systémů jako slitiny ke tváření, ale obsah legur přesahuje

rozpustnost - přítomnost eutektik - dobrá tekutost, nízká náchylnost k segregaci, pórovitosti a vzniku licích trhlin - stejný princip zpevnění (kromě deformačního) - tepelně zpracovávané a nezpracovávané

Light metals

Mechanické vlastnosti a požadovaná pevnost u slévárenských slitin závisejí na faktorech: - velikost zrn - stupeň pórovitosti - přítomnost ostrých hran - možné cyklické zatížení při provozu 1. Hliník 2. Al-Cu 4-6 hm.%Cu, 0,25-0,35 hm.% Mg, + Mn, Cr, (Ag)

Vlastnosti: nejvyšší pevnost a tvrdost do 300°C z odlévaných slitin Al ve slitině vznikají hrubé intermetalické fáze na hranicích zrn �náchylnost ke křehkému

porušení 3. Al- Si siluminy 4,5-22 % hm. Cu

Podeutektické 4,5-10 hm.% Si; eutektické 11-13 hm.% Si; nadeutektické nad 13 % Si Vlastnosti : - Si tvoří již při malém podchlazení ostrohranné útvary a dlouhé jehlice � křehkost

slitiny, čím je chladnutí pomalejší – tím větší a hrubší útvary, pro zjemnění struktury a k potlačení nepříznivého vlivu Si- modifikace sodíkem (0,05-0,08 hm.% Na) – vznik Na2Si, který obaluje částice Si a zamezuje jejich růstu - zvyšuje tekutost, snižuje praskání a vznik ředin další legury : Mg, Cu, Ni, Be � žárupevné slitiny typu Al-Cu, Al- Si - vytvrzené fázemi Al2Cu, Mg2Si, Al2CuMg nebo jejich kombinací

Použití : vyšší obsahy Si – písty a bloky motorů 4. Al-Mg

Vlastnosti : nejhorší úroveň slévárenských vlastností, netvoří eutektikum vysoká obrobitelnost,korozivzdornost, nebezpečí vzniku intermetalických fází na hranicích zrn-křehké porušení – TZ : kalení do oleje

5. Al-Sn (do 6 hm.% Sn) + Cu, Ni

Použití : kluzná ložiska a pouzdra, ložiska klikové skříně u dieselových motorů Rozdělení Al slitin do tříd podle legujících prvků TAB.8.4 Označování slitin hliníku na tváření podle EN 573–1

8.3 Magnesium Vlastnosti : struktura HTU mez pevnosti v tahu 160-365 MPa modul elasticity 45 GPa elektrická vodivost 38,6 % IACS

Hlavní legující prvek Označení série Hliník (min.99% čistota) 1000 Měď 2000 Mangan 3000 Křemík 4000 Hořčík 5000 Hořčík a křemík 6000 Zinek 7000 Jiné prvky – Li, Sc, Fe 8000 Nepoužívá se 9000

Light metals

tepelná vodivost 154,5 W/m.K korozivzdornost na vzduchu dobrá

• ve vodě klesá

reaktivní – reaguje prudce s O2 a na povrchu rychle vzniká oxidická vrstva, vznětlivý nízké mechanické vlastnosti dobrá tvařitelnost za vyšší T tlumivé vlastnosti- výborně absorbuje elastické vibrace

Suroviny MgCl2.6H2O bischofit MgCO3. CaCO3 dolomit MgCO3 magnezit MgCl2.6H2O v mořské vodě

Production Největšími výrobci čistého hořčíku jsou Čína, USA a Rusko

Obr. 8.8 Světoví výrobci pro rok 2012 (zdroj "Magnesium Metal: Global Industry Markets & Outlook 2012", Roskill Information Services Ltd.)

block diagram: magnesium ore → anhydrous MgCl2 → electrolysis → refining→ Mg

příprava bezvodého MgCl2:

z magnezitu kalcinace (700-800°C) MgCO3 → MgO + CO2 chlorace (800-900°C) 2MgO + C + 2Cl2(g) → 2MgCl2 + CO2

z bischofitu dehydratace na MgCl2.6H2O konečná dehydratace v proudu HCl T > Tm MgCl2

Elektrolýza Podle reakce:

MgCl2(l) → Mg(l) + Cl2(g) elektrolyt: 10-12% MgCl2, 75-78%KCl, 6-8%NaCl, 4,5%CaCl2 katoda: ocel anoda: grafit

Složení elektrolytu → proces probíhá při teplotě 680 - 720°C → a to snižuje těkavost MgCl2

Rafinace:

a) přetavením s přísadami – ochrana před oxidací a zestruskování příměsi (chloridy alkalických kovů a KVZ)

Light metals

b) sublimací- využití různé tenze par Mg a příměsi (vakuum 600°C)

čistota 99,92 –99,98 hm.% Mg , zbytek-příměsi: Fe, Si, Ni, Na, Al, Cu,

Silikotermická výroba Kalcinace MgCO3.CaCO3 = MgO.CaO + CO2 - vliv na výtěžnost

Redukce 2MgO.CaO + Si = 2CaO.SiO2 +2Mg(g)

-od poloviny 20. stol.- výhradně pomocí ferosilicia (FeSi75) při T 1150 –1200 °C ve vakuu, + CaF2, (v šachtové odporové peci )

Kondenzace páry Mg kondenzují při 475-550°C do dutého bloku, získaná čistota 2N5

Fig.8.9 Schema of continous silicothermic reduction of magnesium konstrukce zařízení pro nepřetržitou silikotermickou redukci hořčíku, ohřev vsázky elektrickým obloukem, atmosférický tlak, teploty 1700-1750°C

/technologie Mintek Thermal Magnesium Process (MTMP)/ Použití čistého Mg (podle IMA (International Magnesium Association) v r. 2001) : 39 % primárního hořčíku - na legování Al slitin, 38 % primárního hořčíku - na výrobu Mg slitin, zejména pro přesné tlakové odlitky, 13 % primárního hořčíku - na odsíření surového železa směsí prášku Mg + CaO, 10 % primárního hořčíku - na protikorozní Mg anody, redukci jiných kovů (Zr, Ti), Mg prášky pro chemikálie a legování slitin jiných neželezných kovů, pyrotechnika.

Slitiny a jejich rozdělení slitin

1. cast – die casting Mg-Al (Elektron) - up to 10 % Al, upto 6 % Zn, up to 2,5 % Mn, up to 1 % Zr

Mg-Al-Zn-Mn (AZ)

Light metals

Mg-Al-Mn (AM) appication in sea water Mg-Al-Si-Mn (AS) automotive and aircraft industry

Properties: higher strength, low density, good corrosion resistance, high strength at elevated temperatures, good castability, weldability, impropriate for applications in gas contact 2. wrought - cold forming difficult – structure HCP with slip plane (0001) - at elevated temperatures – slip planes (1011) and (1120) are available - with lower deformation rate higher level of plasticity is achieved - výkovky, tyče, pásky, trubky, plechy. Mg-Mn – nízká pevnost, dobré plastické vlastnosti a svařitelnost Mg-Al-Zn - vysoké vlastnosti mechanické, není náchylná ke koroznímu praskání pod napětím Mg-Zn-Zr - vysoké vlastnosti mechanické, není náchylná ke koroznímu praskání pod napětím,

zvýšená tendence ke vzniku trhlin při deformaci zatepla, zhoršená svařitelnost Mg-Al-Mn +Th - náchylná ke koroznímu praskání pod napětím

Vlastnosti hořčíkových slitin Mechanické: většina slitin Mg má specifickou pevnost v tahu srovnatelnou s klasickými

konstrukčními materiály Tvrdost a otěruvzdornost : postačující pro všechny konstrukční prvky s výjimkou velkých abrazí Únavová pevnost : vyšší pro tvářené než pro slévárenské denotation of Mg alloys according to alloying elements

Application aircraft - převodové skříně, převodovky automotive industry – např. konzoly držáku sloupku řízení, konzoly brzdového a

spojkového pedálu, rámy opěradla a spodku sedadla, vana akumulátoru, atd. Electrotechnic industry - anodes, dry batteries, záložní články informační a komunikační technika – kryty a chasis pro audio-video techniku, PC, mobily doprava a překládání zboží - gravitační dopravníky, korečkové dopravníky průmyslové stroje (textilní, tiskařské) – funkčnost při vysokých rychlostech – lehké, aby

byly sníženy odstředivé síly pracovní nástroje jaderná technika – obálky palivových článků jaderných reaktorů

Summary of terms

Bauxit, Bayerova metoda, spékací metoda, tavná elektrolýza, elektrolyt, karbotermická redukce, anodový efekt, trojvrstvá rafinace, silikotermická redukce, silumin, bischofit, spodumen, fluoridový a síranový způsob výroby Be, beryliová měď.

2 písmena 2 číslice 1 písmeno specifikační skupiny (C – třetí skupina daného typu slitiny)

Typ tepelného zpracování AZ91C-T6

Light metals


1. Definujte základní vlastnosti lehkých kovů. 2. Jaká je reaktivita lehkých kovů? 3. Proč není možné vyrábět lehké kovy elektrolýzou z vodných roztoků? 4. Jaké dvě základní technologie se používají při výrobě lehkých kovů? 5. Popište Bayerovu metodu přípravy oxidu hlinitého. 6. Jaké jsou zásadní rozdíly mezi Bayerovou a spékací metodou? 7. Co je to křemíkový modul a k čemu se využívá? 8. Popište elektrolytický proces výroby hliníku. 9. Co je elektrolytem při výrobě hliníku? 10. Jaké jsou rozdíly mezi redukční a rafinační elektrolýzou při výrobě hliníku? 11. Jaké znáte slitiny hliníku? 12. Pro jaké aplikace se jednotlivé typy slitin hliníku používají? 13. Z jakých surovin je možné hořčík vyrábět? 14. V jakém skupenství se redukuje hořčík při silikotermické redukci? 15. Jaké znáte slitiny hořčíku? 16. V jakých oblastech se slitiny hořčíku aplikují?


[1] Periodická tabulka online na http://www.Webelements.com [Cit. 2013-08-20] [2] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5 [3] Gupta, Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.

KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6 [4] Handbook of Aluminium. Volume 1. Physical Metallurgy and Processes. Ed. by TOTEN, E.G., Mc

KENZIE, D.S. New York, 2003, 1296 s. ISBN: 0-8247-0494-0 [5] Handbook of Aluminium. Volume 2. Alloy Production and Materials Manufacturing. Ed. by TOTEN, E.G.,

Mc KENZIE, D.S. New York, 2003, 724 s. [6] Magnesium Alloys and their Applications. Edited by K. U. Kainer WILEY-VCH Verlag GmbH, Weinheim.

798 s. ISBN: 3-527-30282-4 [7] Davis, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [8] periodic.lanl.gov/56.shtml [Cit. 2013-08-20] [9] http://en.wikipedia.org/wiki/Periodic_table [Cit. 2013-08-20] [10] HTTP://WWW.TZB-INFO.CZ/2595-ZISKAVANI-ENERGETICKY-VYZNAMNYCH-PRVKU-Z-

OCEANU-ILITHIUM [CIT. 2013-06-20] [11] HABASHI, FATHI. HANDBOOK OF EXTRACTIVE METALLURGY, VOL. 2-4. WEINHEIM: WILEY-

VCH, C1997, ISBN 3-527-28792-2. [7] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5 [8] Friedrich, H. E., Mordike B.L. Magnesium Technology. Metallurgy, Design Data, Applications. Springer-

Verlag Berlin Heidelberg, 2006. ISBN-10 3-540-20599-3

Refractory metals

9. Refractory metals

9.1 Basic properties of refractory metals Among refractory metals we can include metals, which have a melting point higher then that

one of iron (1536°C) and are extraordinary temperature and wear resistant. Regarding to high melting point this metals and their alloys are creep resistant to relatively high temperatures. Refractory metals can be further devided into two groups according to their crystalline structure (lattice), although some of them submit to allotropic transition (e.g. Ti, Zr):

1. metals with BCC: W, Ta, Nb, Mo, V, Cr 2. metals withs HCP: Ti, Zr, Hf, Tc, Re

Table 9.1 Physical properties of refractory metals

Metal Property

Ti W Mo Ta

Atomic mass (g/mol) 47.9 183.85 95.94 180.9 Density (x103 kg/m3) 4.51 19.32 10.22 16.6 Melting temperature (°C) 1670 3395 2623 2996 Boiling temperature (°C) 3285 5930 4651 5425

9.2 Titanium Properties:

grey to silvery collored metal stable in air even at elevated temperatures (protected by TiO2 oxide layer) stronger by 30%and lighter by 45% then steels o 60% těžší a o 200% odolnější než hliník reaktivnost za ↑T s O2, H2, N2, C ⇒ hydridy, nitridy, oxidy, karbidy ⇒ křehkost S, halogeny ⇒ prchavé sloučeniny odolává mořské vodě a některým kyselinám, rozpouští se v HCl, HF, lučavce královské obecně: dobrá odolnost proti atmosférické korozi a většině průmyslových

a minerálních kyselin pevnost odolnost proti vysokým teplotám poměrně nízká měrná hmotnost

Study time: 2 hours


• define group of refractory metals • describe properties of refractory metals • describe technologies of processing refractory metals • explain methods of titanium processing • list application of refractory metals

Výklad

Refractory metals

Výskyt a suroviny:

Titan je 7. nejrozšířenější kovem v zemské kůře, jeho obsah je odhadován na 5,7 – 6,3 g/kg. Významné zásoby se nalézají v Austrálii, Severní Americe, Skandinávii a Malajsii. Horniny na měsíčním povrchu obsahují přibližně 12 % TiO2 (mise Apollo 17). FeTiO3 ilmenit (nejvýznamnější ruda)

TiO2 rutil (nejvýznamnější ruda) CaTiO3 perovskit CaO.TiO2.SiO2 titanit

Výroba: Titan se vyrábí Krollovou metodou jako tzv. Ti houba, což je porézní materiál. Ten se následně tavením zpracovává na ingoty kovového Ti nebo slitin. Ti reaguje snadno s kyslíkem za vysokých teplot, proto jej nelze redukovat z oxidu TiO2 a provádí se redukce TiCl4 pomocí Mg. Tato metoda- Krollova metoda -je shrnuta v následujícím schématu (Obr.9.1) a sled operací znázorněn na Obr. 9.2 a 9.3 :

Fig. 9.1 Sequencies of Kroll method for Ti processing

Refractory metals

Fig.9.2 Schema of titanium processing using Kroll method including recovery of MgCl2

Fig.9.3 Facility for processing of titanium by means of Kroll method

1- kelímek s víkem, 2- láhev s Ar, 3- termoelektrické články, 4- otvor na odpouštění MgCl2 s chladicím zařízením, 5- manometr, 6- trubka na vyrovnávání tlaku, 7- nádrž na TiCl4, 8- trubka na dávkování TiCl4, 9- ochranný uzávěr, 10- měřidlo množství TiCl4

Refractory metals

Použití:

Titan je kov s perspektivními aplikacemi a pokud by byly nalezeny úspornější metody jeho výroby, mohl by v budoucnu naléze mnohem širší uplatnění než je tomu dnes: Čistý nebo legovaný titan: - legování slitin Ni, Al, Fe aj. - šperkařství, obroučky brýlí, luxusní hodinky - nepřilnavé nádobí, kuchyňské spotřebiče - sportovní vybavení, rámy cyklistických kol - architektura Slitiny na bázi α, β a α+β struktury, jejichž použití je široké a různorodé:

a) konstrukce chemických zařízení - čerpadla, armatury, reaktory, nádrže, výměníky; b) letectví – lopatky turbín, kompresory : slitiny Ti-Al (Sn, Zr, Mo), Ti-V10(Fe, Al),

TiAl6V4 (nejdůležitější slitina s α+β strukturou); c) biokompatibilní materiály - stenty, kloubní náhrady, mikrodlahy, rovnátka,

chirurgické nástroje: TiAl6V4, Ti, Ti-Al, TiNi, aj. d) paměťové slitiny - NiTi, TiNb - jako biokompatibilní materiály, termostatické

součástky, termostatické baterie, aktuátory, materiály tlumicí vibrace, spojovací prvky a další

Sloučeniny: TiO2 – titanová běloba, TiC – slinuté karbidy

9.2 Tungsten Properties: ductile in pure state chemical stability even in moist air unstable in the presence of oxidizing agents oxidation in air at 600 °C → failure

Raw materials: (Fe, Mn)WO4 wolframite CaWO4 scheellite

Processing:

concentrates - by floatation and magnetic concentration: from 2-3% W → to 45-55% W roasting (removal of As, S),

from z wolframitu spékáním (Fe, Mn)WO4 + Na2CO3 = Na2WO4 + (Fe,Mn)O2 +CO teplota 800-900°C loužení v H2SO4 (odstranění P) příprava Na2WO4 - loužením v NaOH

- spékáním s Na2CO3 (800-900 °C) loužení v horké H2O - odstranění Fe, Mn výroba H2WO4 pomocí vroucí HCl Na2WO4 + HCl = H2WO4 + 2NaCl – žlutá sraženina

rafinace H2WO4 překrystalizací z parawolframanu amonného kalcinace → vznik WO3 redukce práškového W - pomocí C, H2, (protiproudně v peci)

I. stupeň: WO3 +H2 = WO2 +H2O (500 -700 °C) II. stupeň: WO2 + 2H2 = W + 2H2O (1000 -1100 °C)

Refractory metals

následné spékání prášku v redukční atmosféře H2 při 3200°C - pomocí Zn, 800 °C, následné loužení v HCl

Use:

• light bulb fibres, arc lamp electrodes, RTG lamps, electric contacts, electrodes of spark plugs, thermal couples for T > 2000 °C, heat resistance up to 2500 °C

• alloyed steels and other alloys • Wolfram Heavy Alloys (WHA) - výroba radiačního stínění,

kontejnery pro přepravu radioizotopů, kolimační systémy pro onkologické ozařovače, penetrátory probíjející vysoce pevné pancíře, vyvažovací závaží v letectví, vysoce tuhé držáky nástrojů s nízkou vibrací a vrtací tyče

Spotřeba wolframu ve světovém měřítku je rozdělena do následujících oblastí (Obr. 9.4): 38 % na výrobu legovaných ocelí, 25 % na výrobu slinutých karbidů, 9 % na výrobu litých karbidů, 14 % na výrobu polotovarů z čistého W a W slitin, 14 % na jiné účely.

Fig.9.4 Oblasti aplikací a spotřeby wolframu (údaj z r.2008)

9.3 Molybdenum Properties: ductile, it can be rolled and soldered chemical stability in air, alkaline or acidic solutions at room temeprature unstable in the presence of oxidizing agents oxidation in air at 800 °C → failure

Raw materials:

MoS2 molybdenit PbMoO4 wulfenit

- together with Sn, W, As, Cu, Bi - very low –grade raw ores

Processing: - flotace molybdenitu – na 90-95% MoS2 - pražením při 650-700°C připraven oxid molybdenový

2 MoS2 +7 O2 = 2 MoO3 + 4 SO2 - rafinace MoO3 - sublimace T= 1000°C - loužením v NH4OH, následně hydrolýza a kalcinace - redukce vodíkem za vzniku molybdenu a vody

I. stupeň: 2MoO3 + H2 = Mo2O5 + H2O II. stupeň: Mo2O5 + H2 = 2MoO2 + H2O (400-450°C) III. stupeň: MoO2 + H2 = Mo + 2H2O (1100°C)

Elektrolytická výroba: Molybden pro vakuovou techniku se vyrábí podobně jako wolfram metodou práškové metalurgie Elektrolyticky:

Refractory metals

- elektrolyt: tetraboritany, chloridy, fluoridy + MoO3 - Mo prášek se lisuje a spéká při 2200-2400°C

Použití:

- slitina (předslitina) ferromolybden, - legura žáruvzdorných ocelí a slitin, speciálních pevných a houževnatých ocelí, rychlořezných ocelí

(s Cr, Ni, Co a V), Mn oceli a slitiny odolné vůči kyselinám, - elektrotechnika – závěsy a jádra vinutí žárovek, součástky spojené se zatavováním do skla a křemene ve vakuové technice, stínítka elektronů, v - chemický průmysl - pletiva a dráty korozivzdorných sít, - legura do Mo dráty slouží jako nosiče wolframového vlákna v žárovkách, - MoS2 sulfid molybdeničitý - černá práškovitá sloučenina- jako mazadlo v extrémních teplotách

nebo tlacích.

Summary of terms

Kroll’s method, Ti sponge, reduction by hydrogen, wolfram heavy alloys


1. Vyjmenujte vlastnosti vysokotavitelných kovů. 2. U kterého vysokotavitelného kovu dochází k alotropické přeměně při poklesu z teploty tavení? 3. Popište Krollovu metodu výroby titanu. 4. Které slitiny titanu znáte? 5. Která nejznámější slitina titanu se používá v letectví i pro medicínské aplikace? 6. Popište technologii výroby wolframu. 7. Co jsou to wolframové pseudoslitiny? 8. Jakým redukčním činidlem se provádí redukce oxidu MoO3? 9. Uveďte oblasti aplikací molybdenu.


[1] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5

[2] Enghag, P. Encyclopedia of the Elements. Technical Data·History·Processing·Aplications, 2004, WILEY-VCH Verlag GmbH & Co KgaA, 1243 s. ISBN 3-527-30666-8

[3] Gupta, Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6

[4] Titanium and Titanium Alloys. Fundamentals and Applications. Ed. by Cristoph Leyens and Manfred Peters. Wiley-VCH GmbH&Co.KGaA, 2003. ISBN 3-527-30534-3

[5] Lassner, E., Schubert, W-D. Tungsten .- properties, chemistry, technology of the element, alloys, and chemical compounds 1999, Kluwer Academic / Plenum Publishers, New York 434 s. ISBN 0-306-45053-4

[6] Davis, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s.

Refractory metals

[7] periodic.lanl.gov/56.shtml [Cit. 2013-08-20] [8] http://en.wikipedia.org/wiki/Periodic_table [Cit. 2013-08-20 [9] HABASHI, Fathi. Handbook of extractive metallurgy, VOL. 2-4. Weinheim: Wiley-VCH, c1997, ISBN 3-

527-28792-2. [10] MOSER, K.D. The Manufacture and Fabrication of Tantalum. JOM, April 1999, s. 29-31

Dispersed metals

10. Rare earth metals

Rare earth elements (REE) or metals (REM) attained the name from the minerals from which they were isolated in past and which were uncommon oxide-type minerals unlike dolomite or magnezite. However, they are neither “rare” in abundance nor "earths”. Their appearance is relatively plentiful in Earth’s crust, for exemple cerium is the 26th most abundant element, neodymium is more abundant than gold and even thulium is more abundant than iodine. Because of their geochemical properties, rare earth elements are typically dispersed and rarely found in economically extractable concentrations. Moreover, their separation is difficult.

Table 10.1 Atomic numbers and densities of rare earth elements

Cerium group (light group metals)

Yttrium group (heavy‐group metals)

Atomic number

Density [g/cm3]

Symbol Element Atomic number

Density [g/cm3]

Symbol Element

21 2.99 Sc Scandium 39 4.47 Y Yttrium 57 6.15 La Lanthanum 64 7.90 Gd Gadolinium 58 6.69 Ce Cerium 65 8.23 Tb Terbium 59 6.77 Pr Praseodym 66 8.55 Dy Dysprosium 60 7.00 Nd Neodymium 67 8.80 Ho Holmium 61 7.22 Pm Promethium 68 9.07 Er Erbium 62 7.52 Sm Samarium 69 9.32 Tm Thulium 63 5.24 Eu Europium 70 6.97 Yb Ytterbium 71 9.84 Lu Lutecium

10.1 Scandium Properties: M = 44.96 g/mol ρ = 2.99 g/cm3 structure = HCP Tm = 1541 °C Tv = 2832°C lehký kov – obobně jako Al – ale vyšší Tm silně elektropozitivní stříbřitě bílý, měkký kov odolný vůči oxidaci (vrstvička oxidu chrání) odolný vůči vodě, vlhkosti a oxidačním kyselinám

Study time: 2 hours


• Define the group of rare earth metals • Specify basic properties of rare earth metals • Describe processing technologies • List applications

Lecture

Dispersed metals

Suroviny a výskyt: V zemské kůře je jeho obsah cca 18-25 ppm (srovnání např. s Co – 20-30 ppm), v oceánech 6.10-7 ppm. Země: Madagaskar, Iveland-Evje Region v Norsku, Syerston a Lake Innes v New South Wales- Austrálie, Čína, Rusko, Kazachstan Skandium je obsaženo v malých obsazích ve velkém počtu minerálů (cca v 800), větší obsah pouze v:

(Sc,Y)2Si2O7 thortveitit (35-40% Sc2O3 ) ScPO4·2H2O kolbeckit vedlejší produkt při zpracování uranových rud (0.02% Sc2O3) nebo rud jiných kovů (Ni, Co,

Fe, Sn, W)

Výroba: vedlejší produkt při výrobě jiných kovů ve formě Sc2O3 - produkce řádově 2 t za rok v r. 2003 – pouze 3 doly vyráběly Sc: uranové a železné doly Zhovti Vody na Ukrajině, doly na

KVZ v Bayan Obo v Číně a apatitové doly na poloostrově Kola v Rusku kovové Sc - produkce 10 kg za rok

princip výroby: 1. Sc2O3 → převedeno na ScF3

2. redukce ScF3 kovovým Ca → kovové Sc

Použití:

Light aluminium-scandium alloys –precipitation strengthening with 0.1 % and 0.5% of Sc for aerospace components, additive in metal-halide lamps and mercury-vapor lamps, 46Sc - radioactive tracing agent in oil refineries legování Al slitin – precipitační vytvrzení s 0,1% a 0,5% Sc →

- letecké slitiny pro Mig 21 a Mig 29 - sportovní vybavení - baseballové pálky, rámy kol, revolvery Smith & Wesson

Sc2O3 - výbojky s velkou svítivostí, ScI3 s NaI - rtuťové výbojky, – radioaktivní izotop – detekční činidlo při rafinaci ropy.

10.2 Lanthanum Vlastnosti: M = 138,91 g/mol ρ = 6,16 g/cm3 struktura = HTU (alotropie) Tm = 918°C Tv = 3470°C stříbřitě bílý, měkký polymorfie s teplotou (při 310 a 865°C) značně reaktivní - snadno oxiduje → La2O3 chemickými vlastnostmi podobný Al (stabilní oxid, který nereaguje s vodou, velmi obtížně se redukuje) s vodou reaguje zvolna → plynný H2 snadno se rozpouští v běžných minerálních kyselinách za zvýšené T - přímo reaguje s B, N, P, S a halogeny ve sloučeninách se vyskytuje pouze v mocenství La3+

Suroviny a výskyt : Lanthan přestože patří mezi rozptýlené kovy, není až tak vzácný. V zemské kůře se vyskytuje v obsahu 32 mg/kg. Vzhledem k vysokému zastoupení La v rudách KVZ , je v současnosti relativní nadbytek La (produkt při výrobě vysoce žádaného Eu nebo Sm). Nejdůležitější rudy:

(Ce, La, etc.)PO4 monazite sands - 2-3% Y

Dispersed metals

((Ce,La)CO3(F,OH) bastnäzite – higher content of La

Výroba: 1. loužení rudy ve směsi H2SO4 a HCl → roztok solí → + NaOH → hydroxidy.

2. separace jednotlivých kovů - metody: • kapalinovou extrakcí, • pomocí ionexových kolon • selektivním srážením nerozpustných komplexních solí.

3. získání kovového La a) redukcí solí kovovým Ca, Li, např. z fluoridu lanthanitého: 2 LaF3 + 3 Ca → 2 La + 3 CaF2 nebo z chloridu lanthanitého (připraveného z oxidu La2O3 + 6 NH4Cl → 2 LaCl3 + 6 NH3 + 3 H2O )

LaCl3 + 3 Li → La + 3 LiCl b) elektrolýzou při zvýšených teplotách – elektrolyt: bezvodý LaCl3 + NaCl nebo KCl

Obr.10.1 Schéma loužení monazitových písků, přípravy solí La3+ a oddělení Th

Použití:

- High refractive index and alkali-resistant glass, flint, hydrogen storage, battery-electrodes, camera lenses, fluid catalytic cracking catalyst for oil refineries

- - v metalurgii - vysoká afinita k O2 → dezoxidace roztavených kovů, - legura → optimalizace

mechanických vlastností slitin (oceli nebo litiny → vyšší tvárnost a kujnost, vyšší mechanickou odolnost proti nárazu, Mo slitiny → nižší tvrdost a vyšší odolnost proti náhlým teplotním změnám);

- sklářský průmysl - oxid lanthanitý La2O3 (→ sklo s vysokým indexem lomu a nízkým světelným rozptylem → výroba optických čoček v objektivech filmových kamer nebo dalekohledech), - s obsahem La → pohlcuje IR záření → optické filtry, propouštějící pouze viditelné světlo;

- petrochemie - krakování ropy - katalyzátory s obsahem La; - lékařství - Fosrenol, Shire Pharmaceuticals - uhličitan La pro absorpci fosfátů při ledvinovém

selhání - atomová absorpční spektrometrie - spektrální iontové pufry; - katoda do elektronových mikroskopů SEM; - NiMH baterie - LaNi3.6Mn0.4Al0.3Co0.7; - brusné a lešticí práškové materiály pro výrobu optických součástek.

Dispersed metals

10.3 Lanthanoids Lanthanoids (lanthanides) are the 14 metals following lanthanum in the periodic table that their

4f orbitals are usually being filled. They are termed as lanthanoids because the lighter elements in the series are chemically similar to lanthanum. Vlastnosti: velmi podobné chemické a fyzikální vlastnosti stříbrolesklá barva velmi měkké velmi reaktivní (Ce, Pr, Nd a Eu) → pokrývají se ox. vrstvičkou jejich reaktivita postupně klesá se stoupajícím atomovým číslem → ost.lanthanidy (Gd, Lu)

zachovávají lesk (neoxidují) s vodou reagují za vzniku plynného vodíku snadno se rozpouští v běžných minerálních kyselinách. za zvýšené teploty přímo reagují s běžnými nekovovými prvky jako N, B, Si, P, S, O a halogeny

→ křehnou chemické vlastnosti solí lanthanidů - značně podobné sloučeninám Al (tvoří vysoce stabilní

oxidy, které nereagují s vodou a jen velmi obtížně se redukují) ve vodě nerozpustné fluoridy a fosforečnany → separace lanthanidů od jiných kovových iontů nerozpustný šťavelan → gravimetrické stanovení těchto prvků po jejich vzájemné separaci Gd - ferromagnetické vlastnosti (podobá se tím Fe nebo Ni) Pr - v přírodě se prakticky nevyskytuje - žádný z jeho izotopů není stabilní a všechny se

radioaktivně rozpadají.

Suroviny a výskyt: (Ce,La,Nd,Th)(PO4,SiO4) monazite sands (Ce,La)CO3(F,OH) bastnäsite (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)2O6 euxenite (Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16 samarskite

Fig.10.2 World production of rare earth metals in 1994-2013 (http://geology.com/articles/rare-earth-elements/)

Dispersed metals

Production: Výroba všech lanthanidů probíhá podobným způsobem. 1. Základní operací je loužení lanthanidových rud směsí kyseliny sírové a chlorovodíkové. Ze

vzniklého roztoku solí se lanthanidy působením hydroxidů alkalických kovů vysráží ve formě svých nerozpustných hydroxidů.

loužení rud ve směsi H2SO4 a HCl → roztok solí → + NaOH → hydroxidy

selektivní oddělení Ce – hydroxid Ce(OH)4 hydrolyzuje z kyselých roztoků a k jeho vysrážení dochází nejdříve.

2. Separace jednotlivých kovů ze sraženiny se provádí různými metodami:

kapalinovou extrakcí, pomocí ionexových kolon selektivním srážením nerozpustných komplexních solí.

3. Získání jednotlivých kovů:

Poslední fází výroby kovových lanthanidů je redukce fluoridů nebo oxidů kovovým vápníkem nebo lanthanem:

v případě lehčích prvků - redukce fluoridů kovovým Ca

2 MeF3 + 3 Ca → 2 Me + 3 CaF2 v případě těžších prvků - redukce oxidů kovovým La

Me2O3 + 2 La → 2 Me + La2O3

některé kovy vzácných zemin se také vyrábějí elektrolýzou směsi roztavených chloridů MeCl + CaCl2 + NaCl

Vzhledem k velmi podobným chemickým vlastnostem a ekonomické náročnosti jejich separace, se pro technické využití některé lanthanidy nevyrábějí jako čisté kovy, ale v různých směsích, například oxidických.

Dispersed metals

Obr.10.4 Schéma výroby KVZ v Mountain Pass. Tučně jsou vyznačeny finální výrobky nebo skupiny výrobků. /Podle USGS Open-File Report 2005-1219/

Použití:

• military uses: night-vision goggles, precision-guided weapons, communications equipment, GPS equipment, batteries and other defense electronics.

¨

http://pubs.usgs.gov/of/2005/1219/of2005-1219.pdf

Dispersed metals

Table 10.2 List of percentage partition in applications of REM

Table 10.3 List of applications of lanthan and lanthanoids

Element Application

La High refractive index and alkali-resistant glass, flint, hydrogen storage, battery-electrodes, camera lenses, fluid catalytic cracking catalyst for oil refineries

Ce Chemical oxidizing agent, polishing powder, yellow colors in glass and ceramics, catalyst for self-cleaning ovens, fluid catalytic cracking catalyst for oil refineries, ferrocerium flints for lighters

Pr Rare-earth magnets, lasers, core material for carbon arc lighting, colorant in glasses and enamels, additive in didymium glass used in welding goggles, ferrocerium firesteel (flint) products.

Nd Rare-earth magnets, lasers, violet colors in glass and ceramics, didymium glass, ceramic capacitors

Pm Nuclear batteries, luminous paint Sm Rare-earth magnets, lasers, neutron capture, masers

Eu Red and blue phosphors, lasers, mercury-vapor lamps, fluorescent lamps, NMR relaxation agent

Gd High refractive index glass or garnets, lasers, X-ray tubes, computer memories, neutron capture, MRI contrast agent, NMR relaxation agent, magnetostrictive alloys such as Galfenol, steel additive

Tb Additive in Neodymium based magnets, Green phosphors, lasers, fluorescent lamps, magnetostrictive alloys such as Terfenol-D

Dy Additive in Neodymium based magnets, lasers, magnetostrictive alloys such as Terfenol-DHo Lasers, wavelength calibration standards for optical spectrophotometers, magnets Er Infrared lasers, vanadium steel, fiber-optic technology Tm Portable X-ray machines, metal-halide lamps, lasers

Yb Infrared lasers, chemical reducing agent, decoy flares, stainless steel, stress gauges, nuclear medicine

Lu Positron emission tomography – PET scan detectors, high-refractive-index glass, lutetium tantalate hosts for phosphors

Summary of terms

Loužení, separace, monazitové písky, kapalinová extrakce, selektivní srážení, magnety, lasery, katalyzátory luminofory.

Application % Catalytic converter 45 Petroleum refining catalysts 25 Permanent magnets 12 Galss polishing and ceramics 7 Metallurgy and alloys 7 Phosphors 3 Others 1

Dispersed metals


1. Definujte prvky ze skupiny rozptýlených kovů a kovů vzácných zemin. 2. Jaké jsou jejich vlastnosti? 3. Kde jsou v PSP umístěny? 4. Jaký je jejich výskyt na Zemi? 5. Kde se těží v současnosti? 6. Jakými metodami se tyto kovy vyrábějí? 7. Na čem je založena jejich separace? 8. Jaké jsou jejich současné aplikace?


[1] Rare Earth Elements: A Review of Production, Processing, Recycling, and Associated Environmental Issues, Engineering Technical Support Center, Office of Research and Development, Cincinnati, OH December 2012 Revised, EPA 6 EPA 600/R-12/572 | December 2012 | www.epa.gov/ord [Cit. 2013-08-10]

[2] Rare Earth Elements online na http://www.bgs.ac.uk/downloads/start.cfm?id=1638 ‎ [Cit. 2013-08-20] [3] ENGHAG, P. Encyclopedia of the Elements. Technical Data·History·Processing·Aplications, 2004,

WILEY-VCH Verlag GmbH & Co KgaA, 1243 s. ISBN 3-527-30666-8 [4] Periodic table. Online on www.Webelements.com [Cit. 2013-08-10] [5] http://www.usgs.gov/ [Cit. 2013-08-10] [6] http://rareearthelements.us/the_17_elements [Cit. 2013-08-10] [7] GUPTA, Ch. K. Extractive Metallurgy of Rare Earths 2005, CRC Press, s.484. ISBN 0415333407 [8] GUPTA, Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co.

KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6 [9] HABASHI, Fathi. Handbook of extractive metallurgy, VOL. 2-4. Weinheim: Wiley-VCH, c1997, ISBN 3-

527-28792-2. [10] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [11] periodic.lanl.gov/56.shtml [Cit. 2013-08-20] [12] http://en.wikipedia.org/wiki/Periodic_table [Cit. 2013-08-20] [13] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5


Radioactive metals

11. Radioactive metals

11.1 Uranium

Uranium is a very heavy metal which can be used as an abundant source of concentrated energy. As a relatively common metal, it is found in rocks and seawater. Indeed, economic concentrations of it are not uncommon. Properties : M = 238.02 g/mol ρ = 19.1 g/cm3

Tm = 1135°C Tv = 3818°C half-life t1/2 238U = 4.468 x 109 years

structure = orthorombic (allotropic transition) paramagnetic na vzduchu se pokrývá vrstvou oxidů rozmělněný na prášek - samozápalný není příliš tvrdý za pokojové teploty se dá kovat nebo válcovat při zahřívání se stává nejprve křehkým, při dalším zvyšování teploty je však plastický hustota při 20 °C - 19,05 g/cm3 (různé zdroje uvádějí údaje v rozmezí 19,05 – 19,20 g /cm3) při

teplotě varu - cca 17,30 g/cm3 uran patří k nejtěžším prvkům vůbec (Pt, Ir, W, Os, Re) - je o cca 70 % těžší než Pb.

Raw materials: Uranium is a relatively common element in the crust of the Earth (very much more than in the mantle). It is a metal approximately as common as tin or zinc, and it is a constituent of most rocks and even of the sea.

UO2 uraninite K2(UO2)2[VO4]2.3H2O carnotite bröggerite, cleveite, nivenite, zippeite, johannite sea water high concentration – 3.3 μg/l (cca 4 mld.tons U totally) coal . Kazakhstan, Canada, USA, Australia, Niger, Namibia, Russia; Increasing mining by leaching in-situ (41% U in 2011)

Study time: 2 hours


• Describe basic properties of uranium • Describe technology of uranium processing • List methods of uranium enrichment • List nuclear and civil applications of uranium

Lecture

Radioactive metals

Processing: 1. leaching - H2SO4, HNO3 or HCl 2. precipitaion of Al, Fe, Co a Mn – addition of Na2CO3 and Ca(OH)2; soluble carbonate is

decomposed by HCl and after addition of amonia U is precipitated as (NH4)2U2O7, then 3. calcination enables forming of U3O8 oxid. 4. carbothermic or metalothermic (Ca, K) reduction of U3O8 oxid to metal

Technologies of enrichment: 1. Elektromagnetic separation 2. Centrifuge enrichment 3. Gaseous diffusion enrichment 4. Atomic vapor laser isotope separation

Application:

1. fuel for nuclear power plants – enriched U by izotope 235U (2 – 4 %)

2. nuclear weaponry - enriched U - concentration of 235U is increased over 95 %

3. depleted uranium – (tuballoy) - counterweights in aircraft, high-density penetrators in army, tank armor (M1 Abrams) and other removable vehicle armor, shielding material in some containers.

Fig. 11.1 World production of uranium in 2001-2011

Summary of terms

In-situ leaching, precipitation, calciothermic reduction, enriched uranium, depleted uranium

Radioactive metals


1. Which minerals contain uranium? 2. Which methods are used for enrichment of uranium used as fuel for nuclear power plants? 3. Can you explain the term of depleted uranium? 4. List the applications of depleted uranium?


[1] ENGHAG, P. Encyclopedia of the Elements. Technical Data·History·Processing·Aplications, 2004, WILEY-VCH Verlag GmbH & Co KgaA, 1243 s. ISBN 3-527-30666-8

[2] Periodic table online on www.Webelements.com [Cit. 2013-08-10] [3] Hewitt, J. Is safe, green thorium power finally ready for prime time? Online na

http://www.extremetech.com/ extreme/143437-uranium-killed-the-thorium-star-but-now-its-time-for-round-two [Cit. 2013-08-10]

[4] GUPTA, Ch. K. Chemical Metallurgy: Principles and Practice. 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 795 s. ISBN: 3-527-30376-6

[5] DAVIS, R. Metal Handbook. DESK Edition, ASM International, 1998, 1521 s. [6] periodic.lanl.gov/56.shtml [Cit. 2013-08-20] [7] http://en.wikipedia.org/wiki/Periodic_table [Cit. 2013-08-20] [8] ASM Handbook. Vol.2, Properties and Selection: Nonferrous Alloys and Special-Purpose Material. 10th

edition, ASM International, 2000, 1328 p. ISBN 0-87170-378-5 [9] World Uranium Production by Country, 2001-2011 online na http://www.intellectualtakeout.org/

library/chart-graph/world-uranium-production-country-2001-2011


processing and properties of nonferrous metals -...

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