prof. dr. christiane schart, helmholz-zentrum dresden-rossendorf

Helmholtz Institute Freiberg for Resource Technology I www.hzdr.de/hif

Recycling of metals by vacuum distillation

and solvent extraction

Christiane Scharf

14th June 2016, Aalto University

METYK Metallialan ympäristö- ja kiertotalous

Prof. Christiane Scharf I Helmholtz Institute Freiberg for Resource Technology I www.hzdr.de/hif

Content

1. Definitions, Explanation

- Extractive metallurgy

- Winning and recycling

2. Examples for recycling of metals

-Vaccum distillation of Ni-Cd-batteries

-Solvent extraction of chloridic solutions (Mg scrap)


Extractive Metallurgy…

…is the pyro- and hydrometallurgical production of metals by all necessary

procedures and equipment from:

– ores (e.g. Fe3O4, Fe2O3, FeCO3, Al(OH)3, MgCO3CaCO3, CuFeS2, ZnS, PbS,

CuAgS),

– earths (e.g. Rare earths/Oxides),

– salts (e.g. NaCl, KCl, MgCl2, KMgCl36H2O, MgSO4H2O) and

– old scrap (e.g. scrap of metals and of electronic devices (WEEE), residues,

catalysts, laser, luminescent substances…)

Ores

Rare earths/Oxides

Salts

Old scrap

Metals p, T, K, DG, DH, DS,…

Pyro-/Hydrometallurgy


Schematic diagram of the winning and recycling of metals

[H. Winterhager, J. Krüger: Vakuummetallurgie

bei der Metallgewinnung, Le Vide, No. 137,

09/10 1968]


• Why is the recycling of metals necessary?

– avoiding waste and saving resources

– saving of energy

– ecological and economical reasons

• Which kind of scraps exists and which one are treated by vacuum

distillation and solvent extraction?

– new scrap (production waste, returns,…),

– old scrap (post consumer scrap,…),

– residues (industrial sludge/slurry, filter cakes,…)


single material

complex material compounds

lifetime of products

material recycling

single material

metallic, ceramic materials, plastics, wood…

Recycling of materials and complex material compounds


Recycling of Ni-Cd-Accumulators (Cd),

Recycling of mercury-containing materials, e.g. compact fluroescent lights (Hg),

Recycling of magnesium scrap (rare earth elements)


In the metallurgy exists two kinds of evaporation

Evaporation of the main metal:

-Mg (winning and recycling)

-Zn (winning and refining)

…

Evaporation of the impurities:

-Cd from Ni-Cd-Accumulators

-Hg from compact luminescent lights, industrial slurry

-Zn from the lead-silver at the lead refining

-Zn from lead at the lead refining

…


72% batteries

13% pigments

8% coatings

6% stabilisers

1% alloys and

others

Recycling of Ni-Cd-Accumulators

Worldwide application of cadmium

[Rentz, Engels, Schultmann, Umweltforschungsplan des Bundesministers für Umwelt, Naturschutz und

Reaktorsicherheit, 2001]


5% cordless phones

0.4% mobile phones

30% battery-driven tools

11% white goods

3% toys 14% consumer

electronics

8% retail

29% emergency

light


Application of Ni-Cd-batteries 1999 (mass-%)

[Rentz, Engels, Schultmann, Umweltforschungsplan des Bundesministers für Umwelt, Naturschutz und

Reaktorsicherheit, 2001]



Schematic setting and reactions

reaction at the positive electrode (cathode):

reaction at the negative electrode (anode):

total reaction:

electrolyte = 20% KOH-solution

e 2Cd(OH)OH 2Cd 2argingch

OH 2

Ni(OH) 2 e 2 OH 2 NiO(OH) 2 2arg

-

2 ingch

2

2arg2

Cd(OH)

Ni(OH) 2 OH 2 Cd NiO(OH) 2 ingch

discharge

discharge

discharge

[Prof. R. Blume, Prof. Blumes Bildungsserver für Chemie,

http://www.chemieunterricht.de/dc2/,

mit Unterstützung des Cornelsen-Verlags]

standard potentials of electrodes:

E(Cd/Cd2+) = -0,81V (in basic solution);

E(NiO(OH)/Ni(OH)2)= +0,49V

absolute voltage = 1,3V

positive pole

safety valve

gasket

cathode

separating

foil, saturated

with electrolyte

anode

minus pole

nickel-plated steel

http://www.chemieunterricht.de/dc2/



Ni-Cd-Cells before closing and beading.

[Dr. L. Trueb, Neue Zürcher Zeitung, Ausgabe

vom Mittwoch, 28. Februar 1996, NZZ Nr. 49, Seite 73,

Rubrik "Forschung und Technik“]

wikipedia: Von Lukas A, CZE - Eigenes Werk, Gemeinfrei,

https://commons.wikimedia.org/w/index.php?curid=9924793

Disassembled Ni-Cd AA cell. 1:outer metal casing (also

negative terminal) 2: separator (between electrodes) 3:

positive electrode 4: negative electrode with current

collector (metal grid, connected to metal casing).

Everything is rolled.



ACCUREC GmbH / RVD-Process (Recycling by vacuum distillation)

S.N.A.M. / Cadmium distillation under normal pressure



ACCUREC GmbH in Essen (Germany)

RVD-process

(Recycling by Vacuumdistillation)

Scheme of the Cd-material flow in the process

[K.-R. Bräutigam, M. Achternbosch, N. Hartlieb, C. Kupsch,

G. Sardemann: Ressourcen- und Abfallmanagement von Cadmium

in Deutschland, Institut für Technikfolgenabschätzung und

Systemanalyse, Wissenschaftliche Berichte FZKA 7315]

cadmium



ACCUREC GmbH, RVD-Verfahren (Recycling by vacuum distillation)

principle of operation:

-one charge = 0.7t old batteries

-p = 30mbar

-first evaporation of the electrolyte and of the

volatile organic compounds at 100 - 150°C

-after that reduction of CdO at 750°C and

nearly complete volatilization of metallic Cd

-in the water-cooled condenser Cd is deposited

from the gas phase => Cd-block

-duration of volatilization and condensation =

5h, for a complete charge 8h

[Rentz, Engels, Schultmann, Umweltforschungsplan des Bundesministers

für Umwelt, Naturschutz und Reaktorsicherheit, 2001]

induction

furnace

condenser

vacuum

pumps




Profiles of pressure and temperature for this process

500°C

0°C

250°C

750°C

pressure

(mbar)

30

1.000

[Rentz, Engels, Schultmann, Umweltforschungsplan des Bundesministers für Umwelt, Naturschutz und Reaktorsicherheit,

2001]

temperature T

electrolyte

volatile organic

compounds

pressure

temperature

time (t) feeding


reaction equations

CO 2 CCO

CO CdCOCdO

CO Cd C CdO

O HCdO Cd(OH)

2

2

22

[Weyhe, R., Friedrich, B.: Vacuum-Thermal Recycling of Used Nickel-Cadmium Batteries, Proceedings of EMC 2001,

Friedrichshafen, p. 175-186]






[Weyhe, R., Friedrich, B.:

Vacuum-Thermal Recycling of

Used Nickel-Cadmium Batteries,

Proceedings of EMC 2001,

Friedrichshafen, p. 175-186]


S.N.A.M. (Société Nouvelle d'Affinage des Métaux) in Viviers (F)

[Rentz, Engels, Schultmann, Umweltforschungsplan des Bundesministers für Umwelt, Naturschutz und Reaktorsicherheit, 2001]


Scheme of the Cd-material flow in

this process




4 Distillation furnaces

principle of operation:

-diameter = 1.60m

-height = 2.30m

-usable volume = 600l

-feeding with round metal baskets,

briquettes of 400 to 1200kg

-Fe and addition of charcoal as

reducing agents

-slowly heating to 900°C

-distillation without vacuum

-process duration = 24h

-cooling = 8h

-Cd-content = 99.95%

-2nd distillation step of Cd is

necessary to minimise the

content of the impurities (30-50ppm)

[Dr. L. Trueb, Neue Zürcher Zeitung, Ausgabe vom Mittwoch, 29. März

1995, NZZ Nr. 74, Seite 77, Rubrik "Forschung und Technik„]




product = high-purity cadmium-sticks

[Dr. L. Trueb, Neue Zürcher Zeitung, Ausgabe vom Mittwoch, 29. März 1995, NZZ Nr. 74, Seite 77, Rubrik "Forschung und Technik„]


Recycling of Magnesium scrap containing

rare earth elements like Y and Nd as alloying

elements

Melting Scrap with chloridic salt mixtures

=> chloridic aqueous solutions containing Y

and Nd

=> solvent extraction for enrichment and

separation of Y and Nd from impurities


Rare earth elements in the periodic table of the elements


World production of

rare earth oxides

from 1950 until 2010

in metric tons

[U.S. Geological Survey]


Rare earth elements

Applications of neodymium, 2000 until 2006

[Naumov, Russian Journal of Non-Ferrous Metals, Vol. 49, No. 1, 2008]

32%

16%12%15%

4%

4% 17%

catalysts of automobiles

metallurgical additives and alloys

polishing agents of glasses and additives for ceramics

luminescentsubstances

permanent-magnets

catalystsof oil refining

Others

Nd-Fe-B

(Nd2Fe14B)

Nd:YAG-Laser

Nd as alloying element Pigment (Nd2O3) in glasses (pink color)


e.g. production of a

Monazite-Sand

(Ce, La, Nb)[PO]4

with 55-60% RE-Oxides

Xenotime

(Y, Eu, Gd…)PO4


Bastnaesite

[Ce, La, (CO3)]F


Rare earth elements, raw materials

Examples of sand, ore and metallic old scrap [Wikipedia, own pictures]

from the shredder fraction light metal fraction

containing RE


Simplified scheme of the production of rare earth oxides from sands, ores and/or old scrap


Rare earth elements, e.g. neodymium, are in a aqueous solution…

…and are treated by solvent extraction.

(i.a. distribution law of Nernst, equilibria in aqueous solutions, composition of

the organic solution/phase, structure and occuring of DEHPA, equipment,

schematic diagram)


Solvent extraction (liquid-liquid-extraction)…

…is a process, which is used in industrial scale for the separation and removal of metals

and/or impurities including the enrichment with an organic phase.

The aqueous solution of a substance (e.g. Nd as NdCl3) will be treated by an organic

extracting agent (e.g. DEHPA), which is not or in very small amounts soluble in the

aqueous phase:

M + E ME, M = metal in the aqueous solution

E = organic phase

ME = organic phase loaded by metal

Extraction

Stripping


solvent extraction

differentiation between the aqueous and the organic phase

consideration of the aqueous phase


Solvent extraction, equilibria in diluted aqueous solutions, Debye-Hückel-equation

-the dependency of the activity coefficient from the concentration in the range of diluted

solutions can be expressed as follows:

mit

-with increasing charge number of the metal ion increases the extractability (+1 < +2 < +3…)

-small ions are better extracted than big ions of the same charge number (ionic radius Al3+ in

crystal structure = 0,54 10-10 m, ionic radius Nd3+ in crystal structur = 0,98 10-10 m) => Al is

easier extractable

21

c

21

23

3

0

2

i

2

Ai I

1000

π2

T) R (ε

e z Nln γ

2

iiczc

2

1I


Solvent extraction, equilibria in diluted aqueous solutions, activity coefficient

Uniting of constants and the use of logarithm to the base 10 result in:

mit A = 0,511

Debye-Hückel-equation for Ic < 0.005 mol/l :

Individual activity coefficient (incapable of measurement):

log += -0.511 z+2 I

log - = -0.511 z-2 I

Mean activity coefficient:

log = -0.511 z+z- I

21

c

2

iiI zA log γ


Development of the activity coefficient Nd3+ dependent on the ionic strength I with

the range of validity of different theories (as example the pH-dependency)

Determination of Nd, aq with the advanced Debye-Hückel-equation

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5

Nd3

+aq

I

C-equationPitzer-Model

Ic > 4 mol/l

advanced

Davies-equation

Debye-Hückel-equation

Ic 0.005 mol/l

advanced

Debye-Hückel-equation

Ic 0.1 mol/l


solvent extraction

differentiation between the aqueous and the organic phase

consideration of the organic phase


Solvent extraction

Composition of the organic phase for rare earth elements

Why Di-(2-ethylhexyl)phosphoric acid as extracting agent?

-it is one of the best investigated, suitable and commercial used extracting agents for rare

earth elements, Uranium, Vanadium, Beryllium, Yttrium, Cobalt, Zinc

Why kerosine as solvent?

-reduction of the high viscosity of DEHPA

-inhibition of the emulsification

-importance for the phase mixing and the phase separation behaviour

Why tributylphosphate as modifier?

-inhibition of the segregation of DEHPA and kerosine in the organic phase (phaenomenon

of segregation appears after long-term usage of the organic phase, this means circles of

„load“ and „de-load“ of the extracting agent)


Solvent extraction

name, structure and occuring of DEHPA

-name: Di-(2-ethylhexyl)phosphoric acid

-chemical formula: C16H35PO4

-dissociation:

P

O

OH

O

O

CH2CH2 CH2 CH2 CHCH3

C H2 5


C H2 5

P

O

O

O

O


C H2 5


C H2 5

+ H+

-Dimerisation by intermolcular hydrogen bonds with

KDimerisation = c(DEHPA)2/c2

DEHPA = 32.000 [div. literature]:

P

O

OH

O

O

P+ P

O

OH

O

O

P

HO O

O O

HO O

O O

R

R

R

R

R

R

R

R

Monomer Dimer

Wasserstoffbrückenbindunghydrogen bond hydrogen bond

monomeric DEHPA dimeric DEHPA


Solvent extraction

Equipment and schematic diagram


Solvent extraction

Schematic diagram of a mixer-settler-unit

aqu.

org.

aqu.

org.

mixer settler

org. phase

aqu. phase

dispersion band

adjusting the level by recirculation of the phase with smaller flow(mostly organic)or by heigth adjustable tanks


Solvent extraction

Schematic diagram of a continous working plant

3-stage countercurrent extraction

aqueous feed with x 0

loadedsolvent

fresh organic feedwith basic load

raffinate

stage 1

stage 2

stage 3

y2x1

x2

y1

y3

x3

y0


Extraction

Stripping with integrated

precipitation as hydroxide

Regeneration

NEW Development

combined extraction-stripping-circuit

KNOWN

separated extracting- and stripping-circuit

aqueous RE-solution

Hydroxides of RE

extractioncircuit

strippingcircuit

aqueous feed

raffinate

loaded organic

organic feed

strip solution

loaded strip

liquor


Quelle: Reuter et al. (UNEP, 2011)

The winning and recycling of metals needs

a deep knowledge of single processes and process-steps

Zn

Sn Fe

Cu

C

Pb

Co

Ca

Mn

Zn

Sn

Fe

Cu

C

Pb

Co

Ca

Mn

Zn

Sn

Fe

Cu C

Pb

Cr

Ni

H/O

W

Au

Mo

Al

Si

Ti

Mg V

Pt

Co

Ca

Mn

Zn

Sn

Fe

Cu

C

Pb

Cr

Ni

H/O

W

Au

Mo

Al

Si

Ti Mg

V

Pt

Ge

Te

In

SE

Sb

Bi

U

P

Ag

Rh

Pd

Ir

Zr

Ta

Hg

Ce

Cd

Ru Os

Ga

As

Li

Ru

K Me

tal/E

lem

en

t U

se

In

ten

sity in

Pro

du

cts

This knowledge is essential to analyse the very complex systems for

ecological impact

resource-efficiency

development of new recycling technologies

economic efficiency


Thank You.

prof. dr. christiane schart, helmholz-zentrum dresden-rossendorf

Presentations & Public Speaking