CHAPTER
P. SOMASUNOARAN K. P. ANANTHAPAOMANABHAN Henry Krumb School of Mines Columbia University New York, New York
16.1 INTRODUCTION
Flotation processes are useful for die separation of a variety of species ranging from molecular and ionic 10 microorganisms and mineral fi~ from one aIIO(bct" for !be pll1KJ5e of extraction of valuable products as well as cleaning of WaSfewalelS. They ~ particularly attlaclive for sepal2tion problems involving very dilute solutions where most oIfICr processes usually fail. The success of ft«ation processes is dependent
... primarily on die 1e1KIerw:;y of surface-active species to conce.-nae 81 dte water-fluid interface and 00 dleir capability to make selected noo-surface-active materials hydrophobic by means of adsorption on them or association with them. Under practical conditions, the amoum of imcrfacial area available for such con- centration is incrQsed by &eftCraling air bubbles or oil ~ in dte ~ solution. A classification of fttXation processes based 00 die ~hanism of separation and die size of die materiaIthat is being separated is given in Table 16.1-1.,.2 Thus. separatioo of surface-active species such as detergents from 8IpIeOU5 solution is koown as foam fractionation while that of noo-surface-active species such as ffiCn:ury and IJIIOSpIIaIcs that can be compIexcd with various surfactants is called molecular flotation or ion notation. The separations of surface-active and noo-surface-active subsieve size coUoids ~ known as foam flotation and micronotation. respectively. F~ ft<Mation is used cu~y for !he separation of subsieve size panic- uIatcs preaggregatcd by various means to die sieve-siu range (Cleveland Cliff Co.). These can be called aggregate notation. Separation of subsieve-size paniculates has been attempted by a number of od1er Icchniqucs using fine bubbles generated by a variety of means or by using oil as die hydrophobic medium. A brief descriptioo of various Rotation processes is given below.
It is to be noted that, although f~ ftOfation of ores is dte only process that has been used inckIstrially ~ a lafIe scale, other notation aechniques have cons:IdcnbIe ~ential for treating dilute solutions and ~ustrial wastes. Examples of potential areas for large-scale application include treatment of primary and secondary sewage efftuents. acid mine drainage, laundry waste, and wastes of textile, paper, leather, dying, printing, and meat ~ing indUstries.
16.2 FLOTATION TECHNIQUES
16.2-1 Froth Flotation
In froth Rotation. fi~t a p'lp of crushed and ground particles in water is conditioned with desired flotation
~
776 P. Somasundaran and K. P. Ananthapadmanabhan BI
TABLE 16.1-1 Flotation Techniques Classified on the Basis of Mechanism of Separation and Size of Material Separated
Nalurdl surface
Ion flotation, molecular flOfation, adsorbing colloid flotation: for example, Sr2+, Pb2+, Hg2+, cyanides
Foam flotation: for example. microorganisms, proteins
In association with sulface- active agents
Microftotation, colloid flotation, ultraftotation: for example, particulates in wastewater, clay, microorganisms
Source: Reprinted from SeparatiQlt and PurijicaliQII Methods, Courtesy of Man:d Dekker, Inc.
Fig. 16.2-1. in the presence of air that is sucked or fed into the impeller zone where the air is well dispersed owing to the intense agitation in that zone. The air bubbles collide with particles and are attached to those that are hydrophobic or have acquired hydrophobicity. The bubble-particle aggregates rise to the top of the cell and are removed by skimming. Various types of machine that are used by the industry have been described in detail by Hams in a recent publication on flotation. I
Two cells used in ~ laboratory for studying the physical chemistry of flotation process are the Hal- limond cell and Fuerstenau cell!') Tests can be conducted in these cells under controlled chemical con- ditions. Tests in a Hallimond tube cell, shown schematically in Fig. 16.2-2. require only about I g of the mineral and do not require the use of a frother. Rigorous control of flotation time, gas flow. and agitation that have been made possible by recent modifications enable one to conduct tests with a reproducibility of :t 1%. Also. application of the results obtained using the HaUimond tube cell has been demonstrated recently by correlating such results with those obtained using conventional laboratory large-scale cells.'
16.2-2 Fine Bubbles Flotation
~
~.
~ ~~: ~ ~ ~'t; ~,
8IXi in die enriching nkJde part of die foamale is ~cled to die lop of die ftor.rion column for ~ftuxing 8I:tM3n .
16.2-] Foam Fractionation
Foam fmctionation involves the removal of nanually surface-active species by aegtjon at low ftow rates in the absence of any agitation. This Ied8Ii'PIe is ~larty useful for die _aI of highly surface- 8;tive contaminants from surfactants used for basic surfaces and colloid dtemistry reseaICh walt.
16.2-4 Foam Flot~tion
,
The a)x)ve ftoWioo when conducted r« microscopic size species dlat are naturally wtface active is called roam ftotation. It has been used under laboratory conditions ror the ~moval or miclOOlJanisms. dyes, alx!
10 00.
~
16.2-5 Ion Flotation
Ion flotation involves separation of ions capable of association with a surfactant from other ions, molecular matter, or waste material from aqueous solutions. In this case, equimolar amounts of surface-active agents often are needed, making it less attractive as a process for recovering valuable products.
16.2-6 Precipitate Flotation (
I
F
c
51
Ions also can be removed fim by precipitating them by changing the pH or by bubbling. for example. hydrogen sulfide in the case of copper. andlhen by providing appropriate surface-active agents that can adsorb selectively on the surface of the precipitate to make it hydrophobic. This process, known as pre- cipitate flotation. has to be conducted under nonturbulent conditions. because the precipitates usually are colloidal and bulky in nature. An interesting variation of the technique, called precipitate flotation of the second kind.6 involves precipitation of the species with an organic reagent so that the resulting precipitate is naturally hydrophobic and can be floated without the help of any additional reagents. Examples of this include flotation of nickel with dirnethylglyoxime!.1
16.2-7 Microflotation
tt ir
Rotation of colloidal-size colligends with the aid of surfactants under mild agitation and aeration conditions is called microflOCation. This technique has been used recently under labo~ conditions for removal of clays and other colloidal mailer from wastewater effluents. It is to be ~ed that the term microflotation also is used by those working on mineral flotation chemistry to froth flotatioo conducted in the laboratory with 1-10 g of mineral feed.
16.2-8 Pressure Release and Vacuum Flotation
1Conventional froth flotation using cells such as that shown in Fig. 16.2-1 usually fail in processing micron- size particles. A basic handicap of the conventional operation is its inability to control the size of bubbles Examples of techniques in which fine bubbles are generated include pressure release flotation and vacuum flotation. Pressure release flotation consists of release of gas predissolved in the pulp under pressure, whereas vacuum flotation involves release of gas nonnally present in the pulp by application of vacuum. In either case, numerous microbubbles are generated on tbe hydrophobic particles causing tfleir levitation. Generation of bubbles preferentially on hydrophobic sites can produce enhanced selectivity. The air pockets in crevices and pores also can act as nucleation sites for the bubbles; this of course can be detrimental.
16.2-9 Electroflotation
1 0 d . b t l f
Bubbles that a~ extremely fine and homogeneous in size can be produced by electrolysis of water using electrodes of a given design. Rotation using such bubbles has been used ~jIoI1edly in Russia in variou~ industries. An attractive featu~ of this technique is that the bubbles resist Coalescence, possibly because of similar charges on the bubble. It has potential for operation ill combination with the conventional flotation (where extemal air is used) for treating ores containing panicles in all size ranges.
Vacuum, pressure release, and electroftotation can be used to remove a variety of materials such as oils, fats, heavy metals, and other suspended solids from municipal or industrial waste.9
16.2-10 Oil Flotation
Thc flotation processes using oil-water interface for collection of panicles are emulsion Rotation al. t liquid- liquid flotation. In the former the reagentized panicles are collected by oil-water emulsion droplets and by aeration of the system. whereas in the latter removal of the panicles collected at the interface is achieved mostly by phase separation. The only cornmen:ial use of emulsion flotation, to our knowledge, is that of the separation of apatite from iron ore at LKAB, Malmberget, Sweden.
16.2-11 Aggregate Flotation
Conventional flotation processes can be made applicable to the treatment of fines simply by preaggregating tbem among themselves or with another carrier material. Techniques in this category include floccflotatlon, carrier flotation (ultraflotation), and spherical agglomeration.
FlOCCFlOTATION A technology with enormous potential in the mineral processing area is selective flocculation accompanied by flotation. Such a process already has become commen;ial for the separation of iron minerals from lo.w- gl'ade iron ore.10 In this case stan:h is used as flocculanl for iron oxide and quanz is floated using amine
..:..l:
Bubble and foam Separations-Ore fkJtation 779
as the collector. Flocculation also can be achieved by the adsorption of polyelectrolytes or ionic species. Past IatKJnIory wort on selective lIocculation deab mostly with binary minetal systems in which the valuable mi~raI was a metal sulfide (galena. pyrite, or sphalerite)'I-ls or a metal or its oxide (hematite. chromite. inMI. and titanium),s-il and the odIer ~ was a g~ mineral. RePOfts of sepaI31ion by selective IIocculation on multicompo~nt natural ~ itself are scant. One noteworthy attempt in this regard is that by Carta et aI.'9 for the be~ficia,ion of uhrafi~ lluorite from latium.
CARRIER FlOTATK>N (UlTRAflOTATK>N) In this technique. known also as piggyback ftotation. a carrier material is used for ftoafing the fine particles. For example. anacase is leDM)Ved on a comrnen:iaI scale from clay for use in the paper iIMiuSUy by using calcile as dae carrier. While anatase does not ftoat by itself. it is coftoated with a coarse auxiliary mineral such as cakite.
An analogous process is one called adsorbing colloid ftotation in which the colligend is adsorbed on a colloid thai can be ftoated using various microftotation lccbnicpJes.zo
SPHERICAL AGGLOMERATION FiDeS ~ tumbled in this case in an IqIJeOUS solution COIIIaiaing an invniscible Iiquic! whidl fOrD1S capillary bridges betwcea ~ ~1es and causes dleir~. Si~ Si(x:k's original observation of this phenomenon in 19.52 with barium sulfate ~CaIes in benzene. containing a small amount of water. it has been examined maialy by Puddington and ~ for ~Iometation of graphite. chalk, zinc sulfide. coal, iron ore, and tin ore suspensions in aqueous solutions. I Also, Farnard ct aI.!! have claimed
good scparation of eacla COII1p)IICnt from a rnixture or li8C sulfide, calcium carlJonate. and graphite in water with nitrobenzene as binding liquid by stepwise agglomeration.
Physicochemical principles governing the varOis tIocMjon processes ~ essentially Mientical. even dKlUgh there can be significant dilferences in the actual mechanics used in their application. Basic principles involved in Rotation ~ discussed below with appropn.te examples.
16.3 PHYSICOCHEMICAL PRINCIPLES
!i The success of selective Rotation depends primarily 00 the diffele1K:CS in the hydrophobicity of the species or particles that ale co be ftO8Icd. Excepc for a smaU flacliOll, colligends a~ generally hydropitilic and the~fo~, to impart hydrophobicitY, surfactants thac seleclively will associate with or adsorb on them ale 8IkIed to the syllem. Thcsc aarfxunts, gencta1ly called coUectors, have at least ~ polar head and ~ hydropitobic tail in their RM)1ccular sllUCtu~. CollectOf$ adsolb on minerals with their hydrophobic tail tIImcd toward the bulk~. rhcreby making rhc minerals hydrophobtc- Typica1 examples of colieclors ~ in praccice include Iong-<:hain amines for quartz, potash, and anionic complc~cs such as fem>cyanide alKl sbort<hain xandIatcs for base mcta1 sulfides.
In the recent past, a number of e~cellent ~vicws and boob have appca~ on the physicochemical aspects of Rotation. 1-6 Only a brief ovcrvicw of the n-=dIaIIistjc 8SpccU ~ included he~ arK! for ~
details ~rs should coosuh the above ~fele1K:CS. The association or adsoqltioo of surfactants with the colli&end ~ occurs due to vari<XIs interactive
fortes, opefaIing iOOivilklally or in COIOOinalion with"each dher. Major forces rhat can contribule to the adsorption arise from elcctroSlatic attraction, covalent bonding, hydrogen bolKling, van dcr Waals cohesive interaction among the adIOIbatc species, arK! solvalion or desoJvation of adsoIbate or adsorbent species in the interfacial region. The concentration c" in kmoI/m}, of coonterions in the interfacial ~gion can be given on the basis of the BoltzmaM distribution function as
( -4G;-S )c. - C. exp -.r--
~;
(16.J.I)
when c. is the concentration in bulk and 40.-s is die f~-eae1JY change involved in the transfer of surfactants from the bulk to the surface of the colligend. Equation (16.3-1) can be rewritten in tenns of adsorption density r, by multiplying the right-hand side by the thickness T of the adsorbed layer:
P. Somasundaran and K. P. Ananthapadmanabhan780
AG~ = AG + AG:.,. + AG..-c + AG:. + AGH + 4G:"v (16.3-3)
AG is the tenD that arises from the electrostatic interaction between ionic species and the charged colligend; similarly, AG:.,. is due to any covalent bonding that leads to chemisorption; 4G..-c is due to the cohesive chain-chain interaction between sunactant species upon adsorption; 4G..., is the nonpolar inter- action between the chain and the solid substrate; 4GH is the term due to hydrogen bonding; and AG:,.v is the result of solvation or desolvation of any species owing to the adsorption process. For each system. one or more of the above terms ~an be contributing, depending on the type of the colligend, sunactant. and other chemical species in the system, concentration of the sunactant, pH, temperatUre, ionic strength, and so on. Thus, for adsorption of alkyl sulfates on nonmetallic minerals such as qualtz, electrostatic and lateral chain-chain interaction forces are considered to playa governing role, whereas for adsorption of xanthates on sulfides, the covalent forces are considered to be predominant.
16.3-1 Electrostatic Forces
Electrostatic properties of the solid surfaces generally result eithec from the preferential dissolution of the lattice ions. as in the case of silver iodide, or from the hydrolysis of the surfaces followed by the pH- dependent dissociation of the surface hydroxyls as in the case of silica: 7
Of(-
-M(HzO)~ ~ -MOH- ~ -MQ-- + HzO
The sign and magnitude of the electrical field is detennined primarily by the concentration of positive and negative (surface) potential-detennining ions. Lattice ions ~ coo~ to be potential.{jetennining ions for Agl-type solids and H" and OH- are the conesponding ions for o~ide minerals. For salt-type minerals such as calcite and apatite. both of the above mechanisms can be operative since their lattice ions can undergo preferential dissolution as well as hydrolysis reactions with H" and OR-. In such cases. H+. OR-. and all charged comple~es that are the result of the hydrolysis reactions can playa major role in detennining the surface potential. Even for the o~ide minerals such as silica. it will be more accurate to consider dissolved hydrolyzed species as potential detennining. since these minerals do have finite solu- bilities that can amount to significant levels. Silicate minerals. with layeJect structures. possess a net negative charge under most natural conditions due to substitutions, for e~. AI)" for Si'" and Mg2+ for AP"
in the structu~. The surface potential +0 for the above minerals is given by
RT (Q+ ) RT (Q- )'to - z:Fla ~ -uta F (16.3-4)
where F is the FaJaday constant and a+ and a- are activiti~ of the positive and negative potential- determining ions with valencies Z. and Z- (inclusive of sign); a~ and aJ'!'C are activities under conditions of zero diarge of the particle surface. Such i condition of zero charge is called the point of zero charge (PZC). Particles will carry a positive charge below the PZC. represented in lenDS of the negative of the logarithm of the positive porentiaI-determining ions. and negatively charged above it. Since the system as a whole must be electrically neutral. there should be an equivalent amount of ions in the interfacial region. called counterions, with charge opposite to that of the particle surface. A schematic diagram of the resultant diffuse soluble layer is given in Fig. 16.3-1.
For oxides and salt-type materials. adsorption of both organic and illO~anic flotation reagents are often the result of electrostatic attraction between the solid and the reagent. The PZC of the solid is an important characteristic property in such cases and can be determined easily by experiment. Typical PZC values of some common minerals are given in Table 16.3-1. It is to be noted that the PZC of the minerals has been shown. using zeta potential. (potential of the shear region) measurements. to be affected significantly by various factors such as pretreatment of the solid. extent of aging. storing. as well as the pH and even the
ionic strength of the solution in which it is stored.4S.6I-1O It has been shown recently that the commonly used cleaning procedures such as leaching in acidic and
hot solutions can affect drastically both the sign and magnitude of the experimentally measured paramet~rs such as the zeta potential. 71.72 In addition to the above mentioned variables. surface chemical heterogeneIty of the.rrticles also can contribute significantly to the range of PZC values that can be obtained for a given
solid.7 An interesting study. in this regard. by Kulkarni and Somasundaran73 involved the analysis of vario.us
spots on a typical hematite particle using scanning electron microscopy. energy dispersive X-ray anal~sls- and Auger spectroscopic techniques. Figure 16.3-2 shows the electron micrograph of a hematite partIcle. Spots E. G. and H shown in the figure were analyzed and the results showed a very high percentage of sifica at spots F and G whereas spot H showed almost JXlre hematile. For this particular sample, whereas the bulk: analysis indicated a silica content of 4 %, surface analysis using the Auger technique gave a value
as high as 50% for the silica content. The presence of such large amounts of silica on the surface will dec~ the PZC of the hematite to lower pH values. It is to be noted that, because of the presence of positive hematite regions on the mineral, the adsorption of anionic surfactants still can take place above the net PZC of the sample. In fact, results from the litemture (see Fig. 16.3-3) indicate the adsorption of anionic surfactants above the net PZC of hematite!4.1s In such cases, the observed adsorption could be due to the surface chemical heterogeneities mther than any chemisorption of the collector as speculated in the past!4.1S In addition, chemical heterogeneity of the particles can contribute significantly k> the range
of PZC values that can be otxained for a given solid. In the case of sulfide minerals, oxidation of the surface also can affect the PZC considerably. As the
pH increases. the surface may get oxidized and the potential obtained at any particular pH may be the net value of the oxide and the sulfide. In fact. it may be possible to obtain two PZC values for such minerals, one corresponding to that of the sulfide at lower pH and the other corresponding to that of the oxide at hi~r pH values. Some of the wide range of values shown in Table 16.3-1. for example, chalcocite. cha1copyrite, pentlandite. and spbaierite, could have resulted partly from such surface oxidation. The role of the electrical nature of the interface in determining ad.sorption can be seen for the case of adsorption of dodecylsulfonate on alumina76 (see Fig. 16.3-4). It can be seen that only below the point of zero charge of alumina, when the solid is positively charged. is there measurable adsorption of the anionic sulfonate. This effect is shown more clearly for the case of calcite. for which adsorption and resultant flotation with cationic amine is significant only above the point of zero charge (see Fig. 16.3-5). Indeed. change in electrical characteristics due to adsorption of inorganic species can affect significantly the ftotation response of the particulates. as will be seen later. Thus, ftotation can be depressed by adding electrolytes that will compete with the ftotation reagents for adsorption in the interfacial region or enhanced by adding those electrolytes that can adsotb specifically and change the charge in the desired di~tion. Depression of alni~ flotation of quartz using monovalent and divalent inorganic cations has been analyzed recently on the basis of the double-layer model and its compression." Toward this purpose we rewrite Eq. (16.3-1) with the .1G~ consisting of the electrical term and a term to account for the specific adsorptjon of the bivalent ion
(16.3-5)
where cp is the specific adsorption energy. Assuming that ",6 is equal to the zeta po~ential, that the adsorption density of the collector ions at the solid-liquid interface is constant for a given amount of flotation and that the addition of electrolytes has 00 effect on the specific adsorption potential of the collector ions, one can
write the following equation for the ratio cNolca. for equivalent flotation:
r~ rHa c~ (cPa. + 2F~ - ~\ ---exp- rBl c:a (16.H)
f&, RT
~
8 9
;<
5.0 3.4
3.8-4.9 6-6.5
3.4
23 24 25, 23 27 28 29. 31 32 27 24 28 28 33 34 28
ABgonite Barite, pBa 3.7-7.0 Calcite, pCa 3.5, ~ 3.0 Celestite Dolomite Eggonite FluoBpatite FluoBpatite (synthetic), pCA 4.4, pF 4.6 Francolite, pHPO. Magnesite Monazite Scheeiite, pCA 4.8 Silver, pAg 4.1-4.6 Silver iodide, pAl 5.6 Silver sulfide, pAg 10.2 Strengite 2.8
Andalusite Augite Bentonite Beryl Biotite Chrysocolla Garnet Kaolinite Kyanite Muscovite Quartz Rhodonite Spodurnene Talc Tounnaline Zireon
782
26
.10
Molybdenite Nickel sulfate Pentlandite Pyrite PylTtlotite SpIIalerite
3.0 2.5-3.0
11.5 6.2-6.9
3.0 2-7.5
Short conditioning time Conditioning time not specified Conditioning time not specified
. Any condition co=sponding to zero eIectrok.inetic potential is ~fe~ to as IEP. In the absence of SlJe'"ific IdsorpcioII PZC = I EP
AI Si Fe FIGURE 16.3-2 (a) Scanning electron micrograph of a hematite sample on which spot analysis was conducted. (b) EDAX analysis of spot G shown in pan (a). Analysis of spot E was similar to that obtained for spot G. (c) EDAX analysis of spot H as shown in pan (a). (After Kulkarni and Somasundaran; 7)
counesy of Elsevier Seuqoia S.A., Lausanne. Switzerland.)
783 ~
61
2 3 4 5 6 7 8 9 10 pH
FIGURE 16.3-3 Zeta potential of natural hematite in sodium dodecylsulfate solution. (Data from Shergold and Mellgren. 74. 7S)
784
785BtiJble and Foam Separations-Ore Flotation
pH FIGURE 16.3-4 Adsor.-ion of dociecylsulronate on alumina as a function of pH. (After Somasundaran and Fuerstenau; 76 courtesy or die American Chemical Society.)
of equivalent flotation and thelefole, by assumption, under constant concentration of the coUector. c:," and c:O ale the conespondin~ ~Ik cooceotmj(X1s of sodium aIMI barium ions and l"- and ~ ale the CO(Je-
sponding zeta potentials. rHo aIMI r" are COI\Side~ in this case to be the ~ii of the hydrated sodium and unhydmed barium ions, JespectiveJy, and ." is the specific adSCJI1Mion ~rgy of I moi of barium ioas. The adsorption of hydrated sodium ion on oxide minerals is nonspecific, since its plesellce is ROC known to ctIange the point of zero c~ of these minerals. Using a val8e of 2 for r""tr" and 3RT for .", we obtain values on the basis of Eq. (16.3-6) for the ratio of c:," c:O for constant Rotation. These dIeOfaical values are seen inTahie 16.3-2 to be in fair agree~t with experimental values. Considering the complex
100. .,'~: .. - .-".
80
.~ ./'
0
pH FIGURE 16.3-S Flotation of calcite with do<iecylammonium acetate (DDAA) and ~ium dodccyl sulfate (DDSO.) solutions. (After Somasundaran aOO Agar;2-' coonesy of Ac8demic Prcss.)
20
I"'. :;;':
-50
~ 70 ~ JO
natu~ of d1e ftWtion process, tI1is ag~~t must be conside~ to provide .. e~1eIIt support for the role of the electrostatic interactions in detennining the flotation of such materials.
16.3-2 ~in-chain Interactions FIGURE at low CI
The zeta poteIMiaI pkJt for alumina given in Fig. 16.3-4 as a fulx:tiOll of pH of ck)(jccylsulfonate soIutioos shows a revenal of slope below about pH 7, suggesting increased adsorption below this pH involving forces in addition 10 ~cal attrxtioo. The adsorption isodIenn oMained for ck)(jccylsulfonate on alumina in fact shows a awted change in slope at a particular sulfact8llt adSOfJJtDI ~ sudI an intcfPretMioD. Based on the experimental observations d1at a INmber of other inletf8cial1WOlJClties such as ~. contact angle, and suspension settling ~te undergo a marlced change in a given surfactant concentmioa raDle, it was proposed that at low concentrations of the surfactant, the surfactant KlnS are adsotbed on the minetal due to electrostatic forces. while at high concentrations adsorption is assisted further by forces arising from latenl associative intelXtKlns of the 8fsorbed surfacwM species (see FilS. 16.3-3-16.3-7). The concentntioo at which such two-dimensional lateral interactions begin has been shown to depend on pH, tempe~ture, and the chemical state and the structure of the surfactant.
16.3-3
dodec) ..1M
compI Al
plSiti
16.:
Surf:
Bubble and Foam SeparationS-Ore Flotation 787
e
SPECIFICALLY 0 COUNTER IONS ~ ADSORBING ,~ COLLECTOR
DEHYDRATED \.~ CATIONS COUNTER IONS
..'0E~ CIII m ~ c fII C C
W I- C W -' 0
L-
0
0
EQUIU8R-* CONCENTRATION OF OLEATE, k..oI/.3
FIGURE 16.M AdS«p.bI iIOttIemI of pocassNm oleate 011 akire at . natural pH of 9.6. (After So- masuada~ 81 CCXIdeSy of A&:ademic PIas.)
pH
FIGURE 16.3-' 0Ian&e in zeta jX)Ientiai of calcite particles as a function of pH at Q)8IsfaIII ionic st~gth 10-3 krnol/m3 KNO1). (After Somasuitdal2n;87 courtesy of Academic Press.)
788
10.0
16.3-5 Structural Compatibility
For the case of anionic flotation of simple salts such IS fluorite, it has been suggested by ~n that hydrogen bonding between the oxygen of the collector and the fluoride species is active and that it is assisted by the electron resonance of the polar groops, the stnlcture of which must be compahDIc with the geometry of the mineral crystal. The role of structural ~~ity also has been examined for the case of soluble 5alts. For example, Fucmenau and Fuerstcnau proposed that the surfactant adsoq)tion OIl soluble 5alts is governed by a matdting of size of the functional groop of the surf8Ctant with that of simtlariy charged lattice ions of the solid. Thus, aminium ions adsorb on sylvite (KCI) IxIt JQ 011 halite (NaCI), owing to the comparable size of the aminium ion and the potassium ion. It is to be noted, however, that this theoty fails to explain why a 1000g-diain aniOllic sulfate will adsorb OIIly OIl KCI - 00 OIl HaCl.
An alternate mechanism in tenus of hydration properties of the solid has been pit forward by Rogers and SdIIIlman91 for the adso~iOll of surfactants 011 soluble 5alts.
16,3-6 Hydration Factors
According to Rogers aIMS Schulman," .tsorpioo 011 soluble salts is govemed by their solvation properties. the ones with the largest ~gative heat of solution being a beUer adSOItJCIIt than the odIers. ~r, this theory provides no adequate expianatiOll for seveml adsoqltiOll systems involving soluble 5alts.
16.3-7 Precipitation
An interesting cons~ration by du Riett involves a condition of p~pilalion of !he surfaclant-laaice ion ~x for iocipienlll<Mation.92 This ~sm has been examineod subsequently in detail by a number of investigators.
16.3--8 Adsorption at Liquid-Air Interface
Even though the ftofation process involves three phases and three interfaces, most re~h work has been solely on the behavior of the solid-liquid interface. This is in spite of the fact that 8dSOfption at the solid- liquid interface. as shown in Fig 16.3-10. is of a considerably smaller magnitude thaa dial at the solid- PI or liquid-gas interface. 9J It is to be DOted that e~cellent co~IatiOt1 has been obtained ~ndy between surfactant 8dSOIptjon at the I~id-gas interface 8I.t ftowion for the hematite-oleate system (see Fig. 16.3- II). It is also important to DOte that the migmMlft of the surfXIant at the liquid-gas interface is ~ dIan its di«usioo from bulk to the interface, as least for this system." Such a migl2tion at the interface CaD help towaRI fastef attainment of ~i~ surfactant ~n density at the solid-gas interface upon the con(act of the Mibble with the particle.
-9 .
DOAA
~
.. eu"-. -10- 10 0e >- t- (j) ~ 10-" 0 z Q t- A. ~ 10-12., 0 « - SOLID-GAS
-_.:.. LIQUID-GAS - SOLID-LIQUID
CONCENTRATI<*. kmol/",3
FIGURE 16.3-10 Comparison of Idso~ or dociecylammonium acetate at dilfe~1 interfaces. (After Somasundaran;93 courtesy or American Instilute of Metallurgical Engineen.)
-15 10 -
1 !., J oj I *
100
4080
0 IIM)86 pH
fiGURE 16.3-11 Comparison of 8oIation properties of 3 x IO-s kmol/m) potassium oleate solutions with final surface pressu~ at 2SoC. (After Kulkarni and Somasundaran;90 courtesy of American Institute
of Chemical Engineers.)
16.3-9 Role of lonomolecular Complexes
Studies of die liquid-gas interfacial properties have 'provided a new insight into the flotation mechanisms by revealing the prominent role of the complexes fonned between different surfactant species in flotation. Surfactants such as fatty acids and amines will undergo hydrolysis in water and produce various complexes depending on the pH of the solution. Thus, oleate will exist in the ionic form in the alkaline pH range, in the molecular form in the acidic range, and in the ionomolecular complex in the intermediate pH range.
RH = R- + H+ ole;' aoid RH = RRH-
ole;. Kid '-n."-- '-"-' R- +-
The role of such ionomolecular complexes has been shown to be a potentially impol1ant factor in flotation. In fact, the pH of maximum flotation recovery for the hernatite-oleate system is found to correspond with the pH where maximum complex fonnation is expected.94 Evidence for the formation of the highly surface- active complex was obtained using surface-tension measurements shown in Fig. 16.3-11. Similarly, the pH of maximum flotation of quartz using amine has been shown to coincide with the pH at which maximum lowering of the adhesive tension of the system and of the surface tension of amine solutions occurs (see Figs. 16.3-12-16.3-14). This is also the pH region in which stable amine-aminium ion complexes can be expected. The thermogravimetric analysis results of Kung and Goddard96 have provided some evidence for the existence of such ionornolecular complexes in the bulk phase also. From these results, the formation of complexes between neutral molecules and ions appears to play an imponant part in their enhanced adsorption and resultant flotation using them. It must be pointed out that such correlation has not been
obtained during studies using tertiary amines.
~. f~1:han
pH FIGURE 16.3-12 AotaIion ~very of qualU as a function of solutjon pH using dodecylammonium acetate as collector for ftowion dumion of.5 aIKIlO s. (After SomasUJ.tafan;" ~nesy of Elsevier S.A..
Lausanne. Switzerland.)
E u
\AI U :: «
pH FIGURE 16.3-13 Adhesion tension of dodecylamlOOOium chloride solution of VaMIs CO(M:efttrations as a function of solution pH. (After Somasundaran;9S courtesy of Elsevier S.A.. Lausanne. SwitzerlaOO.)
791
.701
'0
~
.. 4-10-5 kmol/m' OOAA
10 ... 13
pH fiGURE 16.3-14 Surface tension of 4 X 10-. kmoUm) dodecylamine hydrochloride solution as a function of pH detennined by pendant drop methOO, measu~ 15 s after fonning drop." (After R. W. Smith, personal communication, 1967.)
The mechanism of adsotption of complexes on minerals has not been investigated. It can be noted, however, that the electrostatic factor can be impof1ant in this case also, since the complexes like the monomer ions are charged. In addition, increase in the effective size of the species dIIC to complex fonnation can be expected to make the surfactant less soluble in water and bcncc more active.
16.4 FLOTAIDS
In addition to collectors. a number of othcr cbemical additives are used in flotatton to aid 5epantion by this process. They include Crothers, activalors. IiePfCssants. deactivators,! ftocculants, and dispersants.
16.4-1 Frothers
To produce die desiJed froth stability, nonionic surfactants. such as die sparingly soluble monohydroxylated clesols. usually ale added. panicularly when the collector used is of die shon-chain type. The opcimum concentration of die frother in die system is approximately that at which dlele is a significant change in surface tension with surfactant addition (Fig. 16.4-1). It is possible, even though not proved. that the restoring force that becomes available upon any distention of die bubble to plevent its ruptule might contribute toward die requi!ed froth stability in the flotation cell. Indeed. this is applicable only if the diffusion of the surfactant to the locally extended surface legion is not fast enoogh to !educe die surface PIeSSUIe difference between this legion and the sunounding surface, before the distention is lepai!ed by such pressule diffelence.
In addition to inducing froth stability. frother species can take pan in the overall process of adsorption on the mineral surface. Like die collector species, the frother species also can be expected to migrate to the panicle-gas interface during the time of contact and assist in establishing the attachment of die bubble to the panicle. Coadsorption of frother along with the collector species2~ can be favorable for flotation, possibly because the neutral molecules adsorbed between charged collector ions can reduce the repulsion between the latter species and theleby enhance the overall surfactant adsorption.
16.4-2 Activators
Activators are used for enhancing flotation of the minerals that may not possess any ftotability in their absence. Flotation of quam using calcium salts and of sphalerite using copper sulfate (see Fig. 16.4-2) are typical examples of activation. In the case of oleate flotation of quam in the presence of calcium, activation can be attriooted to electrostatic adsorption of the calcium ions on the negatively charged quartz
50
I
30
z 0 Ui z
, ---,
FIGURE 16.4-1 Di8gI2m iUustl8tiog the conelatioa belween froth stability and swf~ lellsion lowering due to die addition of a surfactant. (After Cooke;' coortcsy of John Wiley & Sons.)
aIMS ~ providing sites for adSOI1Mion of the oIeaIr. colIcdOl' species. Bivaleat ions, IIIMJI\ ~, can revene die sign of the stem potential and thQ cause adIOrp(Joa aIMS ftowionwith collectors that have a clwge of the - sip as that of the miaeraJ (~FiC. 16.4-3).
However, sphalerite activarm by copper sulfate is the result of adIOlption of copper ions on the surface of this mineral, due ID ~-eXchanle processes. The eft"ect of adivMon also can be due to their reactions with the collectors to foml ~nds of low-solubility product. 7
Another typical e~ of activation is that of die o~ or cartMJn8Ie minetals by sodiwn sulfide. For example, in the case of cenusite,' the following reactjons can produce a surface layer of sulfide:
Na~ + HzO ;:!; NaSH + NaOH
NaSH + NaHi'bOz ;:!; 2NaOH + ~
NazS + PbCO) ;:!; ~ + ~
The cenusile surface, which is allefed in the above manner. can be ftoa~ with unthale col~. In certain cases. on die IXher haJJd, it is necessary to .emove allefed su~ using acMIs 10 obtaia ftotation (see Fig. 16.4-4). Acids can also enhance notation fk)SSibly by senerating microbubbles on the minem surface as has been suggested in die case of calcile.9 .
# 100
~ CuSO4'5H20,lbm/tonore
FIGURE 16.4-2 Flotation of pu~ sphalerite. "rile g~1ar minenl. 1000ISO mesh was lloated with xan thate 0.10 lb/tOll. terpineol. 0.20 Ib/ton. sodium ~te. 2.00 Ib/ton. and copper sulfate. as shown (From Ref. 5; courtesy of McGraw-Hili. New York.)
-,\(794 P. Somasundaran and K. P. Ananthapadmanabhan
~ ~
Ca CCM1Centration (mmol/ L)
FIGURE 16.4-3 Effect of amount of Ca2+ in die ftotation of quartz by different surfactanls (From Ref. 6.
16.4-3 Depressants
~nts are organic or inorganic reagents that prevent the collector adsofption on the mineml by intef2C1jng with the mineRl or the collector. Silicates, phosphates, aluminium salts, chromates, and di- chromates are typical inorganic salts used as depressants. The action of sodium silicate in flotation is considered to be due usually to its depressing effect on quartz present in the pulp and to its ability to control the dispersion of the slimes that are present in ~ pulp. The effectiveness of silicates has been related to the degree of polymerization that it can undergo under the given conditions.IO The effect of polyvalent cations in the case offtotation of phosphate or calcite. on the other hand, is attributed primarily to collector precipitation in the presence of these ions.I'.'2 Polyvalent ions also can prevent collector adsorption by causing charge reversal of mineRls. For example, addition of soluble phospIIate can depress flotation of apatite using oleate (see Fig. 16.4-5).
~
~Ie .nd ~m ~r"i--Ore Aot.tion 795
pH fiGURE 16.4-5 Eft"ect of ~e SfJeCies on die ftocatioo of 8I8itell'. K~ 2 x 10-6 knd/m}
-COH. These 1Q&ent5 can act by ~ adsorption on die minerals as wdl as by causing IIoccu..- of . 51- dI8t is ~"bIe for excessive coUector coasunllMioa. Even IhcMIgh such IQgeIMs have been used extensively as modifien, . actual ~hanisms by which .y act ~ oot ulMieBtood totally. SclMIIIz and Cooke" and Balajee and Iwasaki" have shown that the adsorption of stareh on iron oxide ~rials depends 00 the type of staIdI, its ~ntion, the extent of brudling. and so 00. Experime.-s ~ ~Iy 00 die adsorpjon of staldliiId okaIe in die p~ of each other have provided so~ insight into the mechanisms involved here (Ref. 16.3-8). It was found dI8t. in dlis~. the ltart:h does not reduce lIocation by inhibilingdle adsorption of surfactant on calcite particles. In fact. ~ adsorption of oleate on calcite was found to be higher in die ~ of starch than odIefWise: (~Figs. 16.4-6-16.4-8). Similarly. die adsorption of SWt:h also was enhanced by oleate. Deprasion of mineral fIocation obtained under dIr;se conditions suggested that even though die mineral has adsorbed ~ oleate, it has ~mained hydrophilic. This unusual pheno~non was ascribed to the fonnation of the helical-type structure that stareh assumes in the ~ of hydrophobic materials or in alkaline solutions aIM1 to the fact that the interior of dIis helix is hydrophobic aIKI . exterior is hydrophilic. It was sugesled that . adsoftJed oleate is wl3AJcd inside the starch helices. InterKtions between die nonpolar surfactant cI1ajn and the hydrophobic staldl interior can be expected to pr{Kfuce mutual enhancement of adsorptioIi. The hyd~philic nature of calcite in . presence of starch and oleate results from die fact that die adsoI,bed oleate is obscured from die txllk.
.. , . ~ ,~~',~ ,"'" IC~ *
~ "
~/
loci' ~'*'~'~'~l~5 CONCENTRATION OF STARCH, ppm
FIGURE 16.4-6 Adsorption density or oleate on calcite at natural pH 9.6-9.8 IS a runction or stan:h added prior to the oleate additKln. (After Somasundaran. Rer. 16.3-87; counesv or Academic Pre.u.\
~ t796 P. Somasundaran and K. P. Ananthapadmanabhan
solution by Slan:h helices with a hydrophilic exterior and from possible masking of the collector adsorbed on die mineral in the normal manner by massive stan:h species.
Simple organic compounds such as citric acid, tartaric acid, oxalic acid. and EDT A often are used as modiliers.'6 Some of these reagents react by complexing varioos interfering ions such as calcium that are usually present in the solution.
16.44 Deactivat()rS
Deactivators interact with activators to form an inert species and thus prevent activation. An example is the deactivation of copper in the xanthate flotation of sulfides by cyanides.
16.5 VARIABLES IN FLOTATION
A number of variables are encountered in flotatioll due to the variations in the raw materials. methods of their preparation, reagentizing, and the actual flotation p!occss itself. An understanding of the effect of the
kmol/m3 o'eate 0 10- 4
610-5 ~ 0 \&J t- ~ 0 ..J I&.
0 4.5 9 13.5 18 CONCENTRATION OF STARCH, ppm
.
~ 797Bubble ~nd Foam Separ~tions-ore Flotation
variables can help towani proper control of the flotation for optimum perfonnance. The effects of major physical BOO chemical variables have been ~viewed e1sewhe~.1.1
The chemical variables that can play a major role iJK:lude chemical state and SUuclu~ of !he surfxtant. including its d\ain length. concentrations of surfactant. complexing ions. flocculants. and dispersants. pH, ionic st~ngth. BOO !he temperatu~ of !he solution. As mentioned earlier, flotation can be expected to be maximum if the collector is ~nt as iono~1ar complexes. Substitution of hydrogen in !he -CH1- groops of die long chain with fluorine has been fouoo to produce a significant inclease in ftOtalion! Of course. flotation is strongly dependent on collector concentration. Rubin et al.4.' among others have stUdied !he dependence of ~ipilale flotations and ion flOlalions on die ~tration of die collector. While a collector to coIligelMi ratio of 0.2: I normally is rIeceSSaIY for achieving good flotation of precipitates. die ioo flotation was fouoo to need much larger quantitiC$. For foam separation techniques, die most suitable surfac1aDI COIK:entration is die lowest one that provides !he desi~ foaming prqIerties.H Transiency of die fOIm was found desirable for eXUactj()l\ in solUtions of low collector ~rations. In fmh ftotatjoo also, an excess of collector has sometimes been fouoo to produce ~ extraction.'
Flocculants and polymers can cause an inclease or a declease in ftocatjoo depending 00 the properties of !he coIIi&enS. 1005. while flOCation of B ~ and illite with miam lauryl sulfate can be eahanced by Piing alum,lO. II that of calcite and apatite using sodium oIcate can be depressed tot,aJly usinl starch.
The pH of die solution is an important variable controlling flotation since die pH can affect die electrical .-.nies of die particle surfaces BOO its solubility as well as !he clIemicaI state of !he surfactant. The effect of pH due to its role in determining die surface charge of die paIlicles is illustrated in Fil. 16.3-5 whe~ ooly die collector that is charged oppositely to die mineral surface is capable of producing significant ftOIatjoe. The role of pH in determining !he chemical state of oleate and amine and !heRby flOCatioa usins them a- been discussed earlier. Maximum ~ was otMained in ~ cases under pH ~itions that generate ionoroolecular complexes of the collector.
Ionic StJm&dl has a silnificant role to play ia determining die ~ of collector on die mineral as wdl as 00 die tMlbble due to both the incteascd electrical double-layer con..,rcssion and die inclased salting out of die collector from the aqueous solution with increase in ionic strength. Wbile the effect on die double layer will cause a decrease in flotation for sySfems whe~ electrostatic autactioo is a major factor. the salting unit effect will produce an increase in ~. When the iJK:1ease ~ ionic stRagth is the ~It of a salt containing a bivalent counterion. the ~sion of flotation is even larger. This IaIBef effect results from the tendency of the bivalent ions to adsorb strongly and compete with the collector more than the monovalent ions. This effect also can be used 10 activate the 8OIalion of a particle that has a charge similar to dIat of a collector (see Fig. 16.4-3). Enough bivalent ions a~ introduced in this ~ to cause a particle charge ~versal. the~by making the collector adSOl]llion possible.
The effect of variation in the temperatu~ of the pulp or solution or 8IMaIioa has not been studied in detail. Elevation in tempera~ is expected to ~ adsolpCioo of collectors on minerals if die IdSOIption is due to physical foR:eS. and to inc~ adsorption if it is due to chemical foR:eS. An inte~ng observation in this qard has been the ~Its obtained for the flotation of hematite using oleate under various ionic
798
!u 'Su.a- ..
a .E .g £
.
~:ac.!!~"Q , ~cd
;I. .z~.. ... .. ,- ~
. ~ILo c'C0(U"0.cgSU
s
strength conditions. In this case an increase in temperature enhanced flotation but only under low ionic strength conditions (Fig. 16.5-1). Above an ionic strength of 2 x 10-3 kmol/m). flotation was found to decrease with an increase in temperature. These temperature-ionic strength interactions are attributed to be the effect of adsorption of the oleate on the mineral and the salting out of the oleate from the solution. It is to be noted that the alterations in temperature also can affect the performance of a foam separation technique due to its effects on foam drainage, transiency, and adsorption on the bubble surface.
Physical hydrodynamic variables that can affect the flotation, even though not to as great an extent as the clIemical variables listed above, include gas flow rate, bubble size distribution, agitation, feed rate. foam height, and reagent addition RxJdes.
A detailed list of foam separation studies is available in a number of reviews Refs. 16.1-1. 16.1-2. 16.3-6, 16.5-13-16.5.15). A compilation of major minerals and other particulate matter that have been separated by froth flotation are given in Table 16.5.1.
REFERENCES
Section 16.1
P. Somasundaran, Foam Separation Melbods. in E. S. Perry aOO C. J. Vann Oss (Eds.). Sepa- ration and Purification Methods. Vol. I, p. 117. Man:el Dekker. New York, 1972.
P. Somasundaran. Separation Using Foaming Techniques. Sep. Sci., 10,93 (1975).
Section 16.2
16.2-1 C. C. Hams, Flotalioo Machines in M. C. Fuerstenau (Ed.), Flotation, Vol. 1, p. 753, A. M. Gaudin Memorial International Rotation Symposium. AIME, New York, 1976.
16.2-2 D. W. Fuerstenau, P. H. Metzger, and G. D. Seele, Eng. Min. J., 158,93 (1957). 16.2-3 M. C. Fuerstenau, Eng. Min. J., 165, 108 (1964). 16.2-4 R. D. Kulkami, "Flotation Properties of Hematite.oOleate System and Their Dependence 00 the
Interfacial Adsotption," D. Eng. Sci., Dissertation, Columbia University, New York, 1976.
16.2-5 M. Goldberg and E. Rubin, Ind. Eng. Chem. Proc. Des. Dev., 6, 195 (1967). 16.2-6 T. A. Pinfold, Adsorptive Bubble Separation MetIKJds, &po Sri., S, 379 (1970). 16.2-7 E. J. Mahne and T. A. Pinfold, Precipitate Flotation, J. AppL oIem., 18,52 (1968). 16.2-8 E. J. Mahne and T. A. Pinfold, Selective Precipitate Flotation, Chem. Ind., 1299 (1966). 16.2-9 D. B. Chambers and W. R. T. Cottrell, Rotatioo: Two Fresh Ways to Treat Elftuents, Chem.
Eng., 83(16), 95 (Aug. 2, 1976). 16.2-10 R. Sizzelman, Cleveland-Cliffs Takes the Wraps Off Revolutionary New Tilden Ore Process,
Eng. Min. J. 10, 79 (1975). 16.2-11 D. N. Collins and A. D. Read, The Treatment of Slimes, Miner. Sri. Eng., 3, 19 (1971). 16.2-12 S. K. Kuzkin and V. P. Nebera, "Syndletic Rocculants in Dewatering Processes," Trans. J. E.
Baker, National Lending Library, Boston Spa 278, 1966. 16.2-13 O. Griot and J. A. Kitchener, Role Surface Silanol Groups in the Flocculation of Silica Suspen-
sions by Polyacrylamides, Trans. Faraday Soc., 61, 1026 (1965). 16.2-14 A. M. Gaudin and P. Malozemoff, Recovery by Flotation of Mineral Particles or Colloidal Size,
J. Phys. Chem., 37, 597 (1932). 16.2-15 A. D. Read, "Selective Flocculation or Fine Mineral Suspensions," Stevenage, Warren Spring
Lab. Repon LR88 (MST), 1969. 16.2-16 A. D. Read, Selective Flocculation Separation Involving Hematite, Trans. IMM (London), SO,
C24 (1971). 16.2-17 I. Iwasaki, W. J. Carlson, Jr., andS. M. Parmener, The Use of Stan;hes and Stan;h Derivatives
as Depressants, and Rocculants in Iron Ore Beneficiation, Trans. AIME, 244, 88 (1969). 16.2-18 A. D. Read and A. Whitehead, Treatrnenl of Mineral Combinations by Selective Flocculation.
Proc. X Int. Min. Proc. Conp;., IMM (London). 949 (1974). 16.2-19 M. Carta. G. B. Alsano, C. Deal Fa. M. Ghiani, P. Massacci, and F. Satta, "Investigations on
Beneficiation or Ultrafine Fluorite from Latium." Proc. XI Int. Min. Proc. Cong., Paper 41, 1975.
16.2-20 Y. S. Kim and H. Zeitlin, Anal. Chem. Acra, 46, 1 (1969). 16.2-21 H. M. Smith and I. E. Puddington. Spherical Agglomeration of BaSO., Can. J. Chem., 38,
1911 (1960).
f?" 801 Bubble and Foam Separations-Ore Flotation
Section 16.3 16.3-1 M. C. Fuemenau. f1otation. A. M. Gaudin Memorial Vols. I and 2. AIME. New York, 1976.
16.3-2 J. Leja. Surface Chemistry of Flotation, Plenum, New York, 1982. 16.3-3 R. P. King, Principles of Flotation, Sooth African InstitUte of Mining and Metallurgy, Johan-
nesburg. 1982. D. W. Fuerstenau, Froth Flotation, 50th Ann. Vol. AlME. New York. 1962. P. Somasundatan and R. B. Grieves. Interfacial Phenomena of particulatelSollltionlGas Systems. Applications to Flotation Research. AIChE Symp. Ser. Vol. 71, No. 150, AIChE, New York,
1975.16.3-6 A. N. Clarke and D. J. Wilson, Foam f1otation. Theory and Applications, Ma~ Dekker, New
York, 1983.P. Somasundatan. T. W. Healy, and D. W. Fuerstcnau, Surfactant Adsorption at the S/L Inter- face-Dependence of Mechanism on Chain Length, J. Phys. Chem., 68, 3562 (1964).
,-.- Y. G. Berube aJKi P. L. de Bruyn, AdsoqJtion at die Rutile-Solution Interface,J. Colloid Interface
Sci., 17. 305 (1968).16.3-9 P. G. Johansen and A. S. Buchanan. An Appli~on of the Micro-electropho~is Method to the
Study of Surface Properties of Insoluble Ox.ides, Austr. J. Chem., 10,398 (1957). 16.3-10 B. R. Palme1", M. C. Fuerstenau, and F. F. Aplan, Mechanisms Involved in the Flotation of
Ox.ides and Silicates with Anionic Collectors: Part II, Trans. AlME, 158. 261 (1975). 16.3-11 J. Laskowski aJKi S. Sobie1"3j, Zero Points of Charge of Spinel Minerals. Inst. Min. Met., 28.
C163 (1969).16.3-12 M. C. Fucmenau, D. A. Elgillani. and J. D. Miller. Trans. AIME, 147. 11 (1970). 16.3-13 D. W. FuerslenaU and H. J. Modi, St~ming of Potentials of Corundum in Aqueous Organic
Electrolyte Solutions, J. Electrochem. Soc., 106, 336 (1959). 16.3-14 G. A. Parks. lsoelectric Points of Solid Ox.ides. Solid Hydroxides and AcpiCOUs Hydrox.o-complex.
Systems, Chem. Rev., 65. 177 (1965). 16.3-15 D. R. NagaJaj aJKi P. Somasundaran, unpublished results. 16.3-16 I. Iwasaki, S. R. B. Cooke, aJKi A. F. Colombo. Flotation Characteristics of Goethite, U.S. Bur.
Mines. Rep. Invest., No. 5593 (I~).16.3-17 D. W. Fuerstcnau, Interfacial Processes in Mineral/Wate1" Systems, Pure Appl. Chem., 14, 135
(1970).16.3-18 M. Robinson, J. A. Pask. and D. W. F~rstenau, Surface Charge of AlzO) and MgO in AqUCO!lS
Media, J. Am. 0Iem. Soc., 47, 516 (1964).16.3-19 I. Iwasaki, S. R. B. Cooke, and Y. S. Kim, Surface Properties and Flotation Cha1"3cteristics of
magnetite, Trans. AlME, 213, 113 (1962). 16.3-20 M. C. Fucrstcnau and D. A. Rice, Trans. AiME, 141, 453 (1968). 16.3-21 Y. G. Berube aJKi P. L.Bruyn, Electroanal. Chem. Interface Electrochem., 37. 99 (1972).
16.3-22 W. StUmm and J. J. MoTgan, Aquatic Chemistry, Wiley. New York.. 1970. 16.3-23 P. Ney, Zeta Potential and Flotability of Mine1"3ls, in V. D. Frechette ct al. (Eds.). Applied
Mineralogy. Vol. 6, Springe1" Verlag, Wien, 1973 (German text). 16.3-24 G. A. Parks: Aqueous Surface Chemistry of Ox.ides and Complex Oxide Mine~ls. Adv. DIem.
Ser. 6. 121 (1967).16.3-25 P. Somasundatan and G. E. Aga1". The Zero Point of Charge of Calcite, J. Colloid Interface
Sci..14. 433 (1967).16.3-26 M. C. Fuemenau, G. GutiCl"reZ, and D. A. Elgillani, The Influence of Sodium Silicate in Non-
metallic Flotation Systems. Trans. AIME. 141. 319 (1968). 16.3-27 J. J. Predali and J. M. Cases. Zeta Potential of Magnesium Carl!onate in Inorganic Electrolytes.
J. Colloid Interface Sci., 45. 449 (1973). 16.3-28 G. A. Parks. Adsorption in the Marine Environment. in J. P. Riley and G. Skirrow (Eds.).
Chemical Oceanography. 2nd ed.. p. 241, Academic. New York. 1975. 16.3-29 P. Somasunda1"3n. Zeta Potential of Apatite in Aqueous Solutions and Its Change During Equi-
lib1"3tion. J. Colloid Interface Sri., 27, 659 (1968). 16.3-30 P. Somasunda1"3n and G. E. Aga1". Funher Streaming Potential Studies on Apatite in Inorganic
Electrolytes, Trans. SME/AIME, 152. 348 (1972).
16.3-4 16.3-5
~
I
16.3-31 F. Z. SaIeeb and P. L. BlUyn, Surface Properties of AIka1i~ Earth Apatites, Ei«troallDl. ~ Interface Electrodsem., 37, 99 (1972).
16.3-32 M. S. Smani, J. M. Cases. and P. Blazy. Beneficiation of SedimenlaJy Moroccan Phosphate ~-Part I: Electrochemical Properties of Some Mi~rals of the Apatite Group; Part n: EIec- b1XhemicaI PhcIIOI1IeIIa at the Calcite/AcpIeoIIs Interface. TraIlS. 5ME/AIME. 151, 168 (1915).
16.3-33 J. Th. G. OvertJeek, in H. R. Kroft (Ed.) Electn¥.illetic ~ ill Colloid $cieJt£r. Vol. I, Elsevier, New York. 1952.
16.3-34 W. L. F~yberger and P. L. de BlUyn, Electrochemical Dooble Layer on AgzS. J. Phys. DIem., 63, 1475 (1957).
16.3-35 H. S. 0I0i and J. H. Oh. Surface Properties and Aotability of Kyanite and Andalusite. J. Inst. MilL MeIaU., JpIL,ll, 614 (l965).
16.3-36 T. J. Snmlik, X. Hannan. and D. W. Fuerstenau. Surface OIaracteristics and FloIatMJII Bdlavior of Aluminosilicates, T1DIU. AlME. 135, 367 (1966).
16.3-37 M. C. Fuerstenau, B. R. Palmer, and G. B. Gutie~. Med\anisms of Flotation of Selected Iron Bearing Silicates. T1DIU. SAlE/AlME. 10 appear.
16.3-38 I. Iwasaki. S. R. B. Cooke, D. H. HanawaY. and H. S. 00, Fe-Wash Orc Sli~-Mi~ral- ogicaland RocaaMJII ~ Trans. AIME,. W, 97 (1962).
16.3-39 R. W. Smith and N. Trivedi, Van.ioll of PZC of Oxide Minerals as a Function of Aging Ti~ in Water. TraIlS. AIME. 155, 73 (1914).
16.3-40 M. C. FuelStenau, D. A. Rice, P. Somasundaran, and D. W. Fuerstenau, Metal Ion Hydrolysis and Surface 0Iarge in Beryl AotaaMJo. Bull. Inst. MilL Met. ~. No. 701, 381 (1965).
16.~1 J. M. Cases, NomIaI IJI8eractioII Between AdSOIbed Species - Adsorbins Surface, T~. AIME,247, 123 (1910).
16.342 B. R. Pal~r, G. B. Gutie~z, and M. C. Fuerstenau, Medlanisms Involved in the Rotation of Oxides and Silicates with Anionic Collectors: Pan I, Trans. AIME, 258, 257 (1975).
16.3"3 J. M. Cases, Zero Point ofChaI'ge and Structu~ of Silicates. J. aim. PhY5. Phys. 0Iim. Bioi., ", I~ (1969).
16.~5 R. D. Kulkarni and P - Somasundaran. EJfect 01 Aging 00 the Bectrokinetic ~ 01 Quartz in Aqueous Solutions, in Oxide Electrolyt~ I/lterfacu. p. 31, Amr:rican ElectrochemM:al Society. 1972.
16.3-46 A. M. Gaudin and D. W. Fuerstenau, Quam FlotatMJII with Anionic Collectors, Trans. AIME,
102,66(1955). 16.3-47 l. Iwasaki, S. R. B. CCX>ke. and H. S. Cbot. FlotatDI OIaracteristics of Hematite, GeoIhile and
Activated ~ with C-18 Aliphatic Acids and Reialed CCJmlKMlnds. Trans. AlME.12I, 394
(1961). l6.3-48 R. A. Deju and R. B. Bhappu. A Chemical Inletp~tWn of Surface Phenomena in Silicate
Minerals. Trans. AlME. 235, 329 (1%6). 16.~9 A. N. ~kova. DetemIinatioa of the EJe.:tnIkjnctic ~iaI Applicable k) FIocation Pro-
~. ~gQShch RIUl. U, 59 (l967>- 16.3-SO Y. Y. A- ADm, The EJfect of Ruoridt 00 the Flotation of Noo-sulfide Minerals, Part n, Zeta
Potential Measu~~nlS, Stevenage: Wa=n Spring Lab.. ~f. R.R./MP/137, 9. 1964. 16.3-51 O. Huber and J. Weigl, Inftuence of the Electrokinetic Charge of Inorganic Fillers on Diffe~nt
Processes of Paper Making, WodIenbL Papi~rfabr., 97, 359 (1969). 16.3-52 D. A. Rice, D. Sci. Thesis, Coloraclo Sc~ of Mines. 1968. 16.3-53 B. V. Derjaguin and N. D. Shubkjdse. Dependeoce of the FIotability of Antimonite on the
Value of the Zeta Potential, TraIlS. IMM,78, S64 (1~61). 16.3-54 C. A. Ost~icher and D. W. McGlashan. "Surface O~idation of Chalcocite," Paper p~sented
at the Annual AlME Meeting. San FQflCisco, 1972. 16.3-55 P. Ney. ZetapotellliDllUId F1oti~rlxuteit - Min~rak/l. Springer-Verlag, Vienna, 1973. 16.3-56 D. McGlashan. A. Rovig. and D. Podoboik, "Assessment of Interfacial Reactions 01 Chako-
pyrite, TraIlS. AIME. 144,446 (1969). 16.3-57 G. C. Sresly and P. Somasundaran, unpublished ~~ullS 16.3-58 R. O. James and G. A. Parks, Adsorption of Zn (II) at the Hgs (Cinnabar)-Water Interface.
AlChE Symp. &r. No. 150. 71, 157 (1975). 16.3-59 P. C. Neville and R. J. Hunter. "The Control of Sli~ Coatings in Mineral PnKessing." paper
presented at the 4th RACL Electrochemistry Confe~nce Adelaide, 1976. 16.3-60 S. Chander and D. W. Fuerstenau, On the Natural Flolability of Molybdenite, Trans. A/ME,
252,62 (1972).
P. Somasundaran and K. P. Ananthapadmanabhan804
16.3-89 E. Sorensen, On the Adsorption of Some Anionic Collectors on Fluoride Minerals, J. Colloid Int~rfac~ Sri.. 45, 601 (1973).
16.3-90 D. W. Fuerstenau and M. C. Fuerstenau. Ionic Size in FlOCation Collection of Alkali Halides. Trans. AIME, 204, 302 (1956).
16.3-91 J. Rogers and J. H. Schulman, Mechanism of the Selective FlOCation of Soluble Salts in Saturated Solutions, in Proc~~dings of the 2nd Int~rnational Congr~ss on Surface Activity, p. 243, Vol. 01, ButtelWOrths, lA>ndon, 1957.
16.3-92 C. du Rietz. Fatty Acids in Flotation, prog~ in Mineral Dtessing. in Transactions of the 4th International Mineral Dr~ssing Congr~ss. p. 417. Almqvist & Wiksells. Stockholm, 1958.
16.3-93 P. Somasundaran, The Relationship Between Adsorption at Different Interfaces and Flotation Behavior, Trans. SMEIAIME. 241, 105 (1968).
16.3-94 R. D. Kulkarni and P. Somasundaran, Kinetics of Oleate Adsorption at die Liquid/Air Interface and Its Role in Hematite Flotation, in P. Somasundaran and R. B. Grieves (Eds.), Advanc~s in Int~rfaci4J Ph~nornena on Palticulat~ Solution, Gas Syst~ms, Applications to Rotation R~s~arclr, AlOiE Symposium. Series No. ISO. p. 124. AIChE, New York, 1975.
16.3-95 P. Somasundaran. The Role of looomolecular Surfactant Complexes in Flotation, Int. J. Mineral. Proc., 3, 35 (1976).
16.3-96 H. C. Kung and E. D. Goddard, Interaction of Amines and Amine Hydrochlorides, Kolloid z. z. Polym.. 231, 812 (1969).
Section 16.4
16.4-1 S. R. B. Cooke, in H. Mark: and E. J. W. Verwey (Eds.), Advanas ill Colloid Sci., Vol. DI. Interscience. New York:. 1950.
16.4-2 J. H. Schulman and J. Leja. Molecular Interactions at the Solid-Liquid Interface with Special Reference to Rotation at Solid-Particle Stabilized Emulsions, Kolloid-z.. 136, 107 (1954).
16.4-3 J. Leja. Proc. 2nd Int. Con[ Sutface Activity, London, 3, 273 (1957). 16.4-4 J. H. Schulman and J. Leja. inJ. F. Daniellietal. (Eds.), SurfacePhe~na ill Chemistry and
Biology, p. 236. Pergamon, New York:. 1958. 16.4-5 A. M. Gaudin. F1otation, 2nd ed., pp. 310-314. McGraw-Hili. New York:. 1957. 16.4~ F. Z. Saleeb and H. S. Hanna. Rotation of Calcite and Quartt with Anionic Collectors, die
~ing or Activating Action of Polyvalent Ions. J. Chem. U.A.R. (Egypt). U, 237 (1969). 16.4-7 M. C. Fucrstenau. The Role of Metal Ion Hydrolysis in Oxide and Silicate Flocation Systems.
AIDIE Symp. Ser., No. 150, 71 (1975). 16.4-8 V. A. GlemtKJtskii. V. I. Klassen, and I. N. Plaskin. Flotatio(l, translated by R. E. Hammond.
Primary ~n:es. New York:. 1972. 16.4-9 A. K. Biswas. Role of CO2 in the Flotation of Carbonate Minenls. Indian J. Tech.. 5, 187
(1967). . 16.4-10 A. S. Joy and A. J. Robinson. in J. F. Danielli. K. G. A. PankburU. and A. C. Riddiford (Eds.).
Flotation, Recent Progress in Sutface Science. Vol. 2. p. 169. Academic. New York:, 1964. 16.4-11 S. C. Sun. R. E. Snow, and W. I. Purcell. Flotation Characteristics of Rorida Leached :[A)ne
Phosphates Ore with Fatty Acids. Trans. AlME. 208, 70 (1957). 16.4-12 K. P. Anantbapadmanabhan, "Effects or Dissolved Species on the Flotation Properties of Calcite
and Apatite." M.S. Thesis, Columbia University. New York:, 1976. 16.4-13 H. S. Hanna and P. Somasundaran. in M. C. Fuerstenau (Ed.). Flotation of Salt Type Minerals
in Flotation, A. M. Gaudin Memorial Volume, AlME. New York:. 1976. 16.4-14 N. F. Schultz and S. R. B. Cooke. Froth Rotation of Iron Ores, Ind. Eng. Chem.. 45, 2767
(1953). 16.4-15 S. R. Balajee and I. Iwasaki. Adsorption Mechanisms or Stan:hes in Rotation and Flocculation
or Iron Ores, Trans. A/ME. 244,401 (1969). 16.4-16 F. F. Aplan and D. W. Fuerstenau. Principles of Non-Metallic Mineral Flotation, in D. W.
Fuerstenau (Ed.). Froth Flotation, 5<Xh Ann. Vol.. AIME. New YOB, 1962.
Section 16.5
P. Somasundaran, Interfacial Chemistry of Particulate Rotation, in P. Somasundaran and R. B. Grieves (Eds.), Advances in Interfacial Phenomena on Particulate Solution/Gas Systems. Appli. cations to Flotation Research. AIChE Symposium Series No. ISO. p. I. AIChE. New York. 1975.
805Bubble and Foam Separations-Ore Flotation
16.5-2 M. C. Fuerstenau and B. R. Palmer, Anionic Flotation of Oxides and Silicates, in M. C. Fuerstenau (Ed.), Flotation, A. M. Gaudin Memorial Vol~, AIME, New Yor1c, 1976.
16.5-3 P. Somasundaran and R. D. Kulkarni, Effect of Chainlength of Perfluoro Surfactants as Collec- tors, TraIlS. IMM, 82, cl64 (1973).
16.54 A. J. Rubin, J. D. Johnson and C. Lamb, Comparison of Variables in Ion and P~ipitate Flotation, Ind. Eng. Chem. Proc. Des. Dev., 5, 368 (1966).
16.5-5 A. J. Rubin and W. L. Lapp, Foam Fractionation and Precipitate Flotation, Sep. Sci.,', 357
(1971). R. W. Schneff, E. L. Gaden, E. Microcznik, and E. Schonfeld, Foam Fractionation, Chem. Eng. Prog., 55, 42 (1959). H. M. Schoen, E. Rubin, and D. Ghosh, Radium Removal from Uranium Mill Waste Water, J.
WaterPollut. Comr. F~d., 34,1026 (1962). 16.5-8 R. B. Grieves, Foam Separation for Industrial Wastes: Process Selection, J. Water PollUtion
COIIlrol Federation 42, R336, 1970. 16.5-9 P. Somasundaran and B. M. Moudgil, The Effect of Dissolved HydrocaJbon Gases in Surfactant
Solutions on Froth Flotation of Minerals, J. Colloid llllerfac~ Sci., 47, m (1974). 16.5-10 A. J. Rubin, in Adsorp'i~ Bubble Separotion Tec/tniques, p. 216, Academic, New York, 1972. 16.5-11 R. B. Grieves and D. Bhattacharya, Foam Sepantion ofComplexed Cyanide, J. Appl. Olein.,
19, liS (1969). 16.5-12 R. D. Kulkarni and P. SomasuIKlaran, Effects of Reagentizing Temperatu~ and Ionic St~gth
and Their Interactions in Hematite Flotation, TraIlS. SME,262. 120-125 (1977). 16.5-13 E. Rubin and E. J. Gaden, Jr., Foam Sepamion, in H. M. SciK)eD (Ed.), New Chemical Engi-
n~ering Separation and T~chniques, Interscience, New York, 1962. 16.5-14 R. Lemlich, Principles of Foam Fractiooation, in E. S. Peny (Ed.), Progress in Separati(}ft and
Purification, Vol. I, p. I, Interscience, New Yor1c, 1968. 16.5-15 R. B. Grieves, Foam Separations: A Review, Chem. Eng. J., 9, 93 (1975). 16.5-16 A. T. Kuhn, The Electrochemical Treatment of Aqueous Eftluent Streams, in J. O'M. Bockris
(Ed.), Electrochemistry of a Cleaner Envirollmelll, Plenum, New York, 1972. 16.5-17 S. W. Reed and F. F. Woodland, Dissolved Air Flotation of Poultry Processing Waste, J. WPCF,
48. 107 (1976). 16.5-18 L. Logue and E. A. Hassan, Jr., "Peeling of Wheat by Aotation," Denver Bull., FIO-BI6.
16.5-19 N. H. GDce, G. J. Klassen, and R. W. Watson, Denver Bull., FIO-B21. 16.5-20 C. A. Roe, "Froth Flotation, Industrial and Chemical Application," Denver Bull., FIO-B46. 16.5-21 J. W. Jelks, "Flotation Opens New Horizons in the Pa~r Industry," Denver Bull., FIO-B64. 16.5-22 S. H. Hopper and M. C. McCowen, .. A Flotation Process for Water Purification," Denver Bull.,
FIO-B71.
16.5.0
'(\,\-1