B u b b l e a n d F o a m S e p a r a t i o n s —

O r e F l o t a t i o n

P. SOMASUNDARANK. P. ANANTHAPADMANABHANHenry Krumb School of MinesColumbia UniversityNew York, New York

16.1 INTRODUCTIONFlotation processes are useful for the separation of a variety of species ranging from molecular and ionicto microorganisms and mineral fines from one another for the purpose of extraction of valuable productsas well as cleaning of wastewaters. They are particularly attractive for separation problems involving verydilute solutions where most other processes usually fail. The success of flotation processes is dependentprimarily on the tendency of surface-active species to concentrate at the water-fluid interface and on theircapability to make selected non-surface-active materials hydrophobic by means of adsorption on them orassociation with them. Under practical conditions, the amount of interfacial area available for such con-centration is increased by generating air bubbles or oil droplets in the aqueous solution. A classification offlotation processes based on the mechanism of separation and the size of the material that is being separatedis given in Table 16.1-I.1'2 Thus, separation of surface-active species such as detergents from aqueoussolution is known as foam fractionation while that of non-surface-active species such as mercury andphosphates that can be complexed with various surfactants is called molecular flotation or ion flotation.The separations of surface-active and non-surface-active subsieve size colloids are known as foam flotationand microflotation, respectively. Froth flotation is used currently for the separation of subsieve size partic-ulates preaggregated by various means to the sieve-size range (Cleveland Cliff Co.). These can be calledaggregate flotation. Separation of subsieve-size particulates has been attempted by a number of othertechniques using fine bubbles generated by a variety of means or by using oil as the hydrophobic medium.A brief description of various flotation processes is given below.

It is to be noted that, although froth flotation of ores is the only process that has been used industriallyon a large scale, other flotation techniques have considerable potential for treating dilute solutions andindustrial wastes. Examples of potential areas for large-scale application include treatment of primary andsecondary sewage effluents, acid mine drainage, laundry waste, and wastes of textile, paper, leather, dying,printing, and meat processing industries.

16.2 FLOTATION TECHNIQUES

16.2-1 Froth Flotation

In froth flotation, first a pulp of crushed and ground particles in water is conditioned with desired flotationreagents including pH modifiers and surfactants. Then it is agitated in a cell, as shown schematically in

C H A P T E R I 6

TABLE 16.1-1 Flotation Techniques Classified on the Basis of Mechanism of Separation and Sizeof Material Separated

Size Range

Mechanism Molecular Microscopic Macroscopic

Natural surface Foam fractionation: for Foam flotation: for example, Froth flotation ofactivity example, detergents microorganisms, proteins nonpolar minerals: for

from aqueous solutions example, sulfurIn association Ion flotation, molecular Microflotation, colloid Froth flotation: for

with surface- flotation, adsorbing flotation, ultraflotation: for example; mineralsactive agents colloid flotation: for example, participates in such as silica

example, Sr2+, Pb2+, wastewater, clay, Precipitate flotationHg2+, cyanides microorganisms (1st and 2nd kind): for

example, ferrichydroxide

Source: Reprinted from Separation and Purification Methods, Courtesy of Marcel 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 dispersedowing to the intense agitation in that zone. The air bubbles collide with particles and are attached to thosethat are hydrophobic or have acquired hydrophobicity. The bubble-particle aggregates rise to the top ofthe cell and are removed by skimming. Various types of machine that are used by the industry have beendescribed in detail by Harris in a recent publication on flotation.'

Two cells used in the laboratory for studying the physical chemistry of flotation process are the HaI-limond cell and Fuerstenau cell.2'3 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 1 g of themineral and do not require the use of a frother. Rigorous control of flotation time, gas flow, and agitationthat have been made possible by recent modifications enable one to conduct tests with a reproducibility of± 1 %. Also, application of the results obtained using the Hallimond tube cell has been demonstrated recentlyby correlating such results with those obtained using conventional laboratory large-scale cells.4

16.2-2 Fine Bubbles Flotation

In contrast to froth flotation, foam separation techniques generally use low aeration rates without any intenseagitation. Foam containing the colligend, called foamate, is collected by suction or overflow and then isbroken by chemical, mechanical, or thermal methods.5 A schematic diagram of a typical foam separationunit is given in Fig. 16.2-3. Recovery and grade of the product can be increased by introducing a strippingand enriching mode, respectively. In the stripping mode, the descending feed is introduced into the foam

FROTHCONTAININGHYDROPHOBICa ENTRAPPEDMATERIALS

AIR

SUSPENSIONTAILS

CONTAININGUNFLOATEDMATERIALIMPELLER

FIGURE 16.2-1 Schematic diagram of a flotation cell.

FIGURE 16.2-2 Modified Hallimond tube.

and in the enriching mode part of the foamate is recycled to the top of the flotation column for refluxingaction.

16.2-3 Foam Fractionation

Foam fractionation involves the removal of naturally surface-active species by aeration at low flow ratesin the absence of any agitation. This technique is particularly useful for the removal of highly surface-active contaminants from surfactants used for basic surfaces and colloid chemistry research work.

16.2-4 Foam Flotation

The above flotation when conducted for microscopic size species that are naturally surface active is calledfoam flotation. It has been used under laboratory conditions for the removal of microorganisms, dyes, andsoon.

FIGURE 16.2-3 Schematic diagram of a foam sep-aration unit.AIR

UNDERFLOW

FEEDRECYCLE

FOAMATEPRODUCT

FOAMBREAKER

CORK STOPPER

PREPURIFIEDNITROGEN

FRITTEDGLASS DISK

MAGNETICSTIRRER

STIRRINGBAR—*

9-mm TUBINGCONCENTRATE

STEM

GROUNDJOINT-"

WATERSLEVEL

TOFLOW-METER

16.2-5 Ion Flotation

Ion flotation involves separation of ions capable of association with a surfactant from other ions, molecularmatter, or waste material from aqueous solutions. In this case, equimolar amounts of surface-active agentsoften are needed, making it less attractive as a process for recovering valuable products.

16.2-6 Precipitate Flotation

Ions also can be removed first by precipitating them by changing the pH or by bubbling, for example,hydrogen sulfide in the case of copper, and then by providing appropriate surface-active agents that canadsorb 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 arecolloidal and bulky in nature. An interesting variation of the technique, called precipitate flotation of thesecond kind,6 involves precipitation of the species with an organic reagent so that the resulting precipitateis naturally hydrophobic and can be floated without the help of any additional reagents. Examples of thisinclude flotation of nickel with dimethylglyoxime.7'8

16.2-7 Microflotation

Flotation of colloidal-size colligends with the aid of surfactants under mild agitation and aeration conditionsis called microflotation. This technique has been used recently under laboratory conditions for removal ofclays and other colloidal matter from wastewater effluents. It is to be noted that the term microflotationalso is used by those working on mineral flotation chemistry to froth flotation conducted in the laboratorywith 1-10 g of mineral feed.

16.2-8 Pressure Release and Vacuum Flotation

Conventional 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 vacuumflotation. Pressure release flotation consists of release of gas predissolved in the pulp under pressure,whereas vacuum flotation involves release of gas normally present in the pulp by application of vacuum.In either case, numerous microbubbles are generated on the hydrophobic particles causing their levitation.Generation of bubbles preferentially on hydrophobic sites can produce enhanced selectivity. The air pocketsin crevices and pores also can act as nucleation sites for the bubbles; this of course can be detrimental.

16.2-9 Electroflotation

Bubbles that are extremely fine and homogeneous in size can be produced by electrolysis of water usingelectrodes of a given design. Flotation using such bubbles has been used reportedly in Russia in variousindustries. An attractive feature of this technique is that the bubbles resist coalescence, possibly becauseof similar charges on the bubble. It has potential for operation in combination with the conventional flotation(where external air is used) for treating ores containing particles in all size ranges.

Vacuum, pressure release, and electroflotation can be used to remove a variety of materials such asoils, fats, heavy metals, and other suspended solids from municipal or industrial waste.9

16.2-10 Oil Flotation

The flotation processes using oil-water interface for collection of particles are emulsion flotation at. i liquid-liquid flotation. In the former the reagentized particles are collected by oil-water emulsion droplets and byaeration of the system, whereas in the latter removal of the particles collected at the interface is achievedmostly by phase separation. The only commercial use of emulsion flotation, to our knowledge, is that ofthe 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 preaggregatingthem among themselves or with another carrier material. Techniques in this category include floccflotation,carrier flotation (ultraflotation), and spherical agglomeration.

FLOCCFLOTATION

A technology with enormous potential in the mineral processing area is selective flocculation accompaniedby flotation. Such a process already has become commercial for the separation of iron minerals from low-grade iron ore.l0 In this case starch is used as flocculant for iron oxide and quartz is floated using amine

as the collector. Flocculation also can be achieved by the adsorption of polyelectrolytes or ionic species.Past laboratory work on selective flocculation deals mostly with binary mineral systems in which thevaluable mineral was a metal sulfide (galena, pyrite, or sphalerite)1 u t 5 or a metal or its oxide (hematite,chromite, iron, and titanium)15"18 and the other component was a gangue mineral. Reports of separationby selective flocculation on multicomponent natural ores itself are scant. One noteworthy attempt in thisregard is that by Carta et al.19 for the beneficiation of ultrafine fluorite from latium.

CARRIER FLOTATION (ULTRAFLOTATION)In this technique, known also as piggyback flotation, a carrier material is used for floating the fine particles.For example, anatase is removed on a commercial scale from clay for use in the paper industry by usingcalcite as the carrier. While anatase does not float by itself, it is cofloated with a coarse auxiliary mineralsuch as calcite.

An analogous process is one called adsorbing colloid flotation in which the colligend is adsorbed on acolloid that can be floated using various microflotation techniques.20

SPHERICAL AGGLOMERATIONFines are tumbled in this case in an aqueous solution containing an immiscible liquid which forms capillarybridges between reagentized particles and causes their aggregation. Since Stock's original observation ofthis phenomenon in 1952 with barium sulfate precipitates in benzene, containing a small amount of water,it has been examined mainly by Puddington and coworkers for agglomeration of graphite, chalk, zincsulfide, coal, iron ore, and tin ore suspensions in aqueous solutions.21 Also, Farnard et al.22 have claimedgood separation of each component from a mixture of zinc sulfide, calcium carbonate, and graphite inwater with nitrobenzene as binding liquid by stepwise agglomeration.

Physicochemical principles governing the various flotation processes are essentially identical, eventhough there can be significant differences in the actual mechanics used in their application. Basic principlesinvolved in flotation are discussed below with appropriate examples.

16.3 PHYSICOCHEMICALPRINCIPLES

The success of selective flotation depends primarily on the differences in the hydrophobicity of the speciesor particles that are to be floated. Except for a small fraction, colligends are generally hydrophilic andtherefore, to impart hydrophobicity, surfactants that selectively will associate with or adsorb on them areadded to the system. These surfactants, generally called collectors^ have at least one polar head and onehydrophobic tail in their molecular structure. Collectors adsorb on minerals with their hydrophobic tailturned toward the bulk solution, thereby making the minerals hydrophobic. Typical examples of collectorsused in practice include long-chain amines for quartz, potash, and anionic complexes such as ferrocyanideand short-chain xanthates for base metal sulfides.

In the recent past, a number of excellent reviews and books have appeared on the physicochemicalaspects of flotation.1'6 Only a brief overview of the mechanistic aspects are included here and for moredetails readers should consult the above references.

The association or adsorption of surfactants with the colligend species occurs due to various interactiveforces, operating individually or in combination with each other. Major forces that can contribute to theadsorption arise from electrostatic attraction, covalent bonding, hydrogen bonding, van der Waals cohesiveinteraction among the adsorbate species, and solvation or desolvation of adsorbate or adsorbent species inthe interfacial region. The concentration C5, in kmol/m3, of counterions in the interfacial region can begiven on the basis of the Boltzmann distribution function as

(16.3-1)

when cb is the concentration in bulk and AGJ - s is the free-energy change involved in the transfer ofsurfactants from the bulk to the surface of the colligend. Equation (16.3-1) can be rewritten in terms ofadsorption density F, by multiplying the right-hand side by the thickness r of the adsorbed layer:

(16.3-2)

In the case of an inorganic species, T can be assumed to be equal to its diameter in the hydrated ordehydrated form as the case may be. Even though a similar assumption has been made in the past withrespect to surfactants, it must be noted that in this case r can vary anywhere from the cross-sectionaldiameters of the molecule (for flat adsorption on particles) to the diameter of a partially coiled moleculeor even that of a fully extended molecule (for surface micellization). AGJ15, the driving force for adsorption,will be the sum of a number of contributing forces as shown below:

AGa°ds = AG°ICC + AGC°OV + AGC% + AGC°S + AGS + A % v (16.3-3)

AGe°,cc is the term that arises from the electrostatic interaction between ionic species and the chargedcolligend; similarly, AG°OV is due to any covalent bonding that leads to chemisorption; AGc.c is due to thecohesive chain-chain interaction between surfactant species upon adsorption; AG£S is the nonpolar inter-action between the chain and the solid substrate; AGg is the term due to hydrogen bonding; and AG£|V isthe result of solvation or desolvation of any species owing to the adsorption process. For each system, oneor more of the above terms can be contributing, depending on the type of the colligend, surfactant, andother chemical species in the system, concentration of the surfactant, pH, temperature, ionic strength, andso on. Thus, for adsorption of alkyl sulfates on nonmetallic minerals such as quartz, electrostatic and lateralchain-chain interaction forces are considered to play a governing role, whereas for adsorption of xanthateson sulfides, the covalent forces are considered to be predominant.

16.3-1 Electrostatic Forces

Electrostatic properties of the solid surfaces generally result either from the preferential dissolution of thelattice 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

The sign and magnitude of the electrical field is determined primarily by the concentration of positive andnegative (surface) potential-determining ions. Lattice ions are considered to be potential-determining ionsfor Agl-type solids and H+ and OH" are the corresponding ions for oxide minerals. For salt-type mineralssuch as calcite and apatite, both of the above mechanisms can be operative since their lattice ions canundergo preferential dissolution as well as hydrolysis reactions with H+ and OH~. In such cases, H+ ,OH ~, and all charged complexes that are the result of the hydrolysis reactions can play a major role indetermining the surface potential. Even for the oxide minerals such as silica, it will be more accurate toconsider dissolved hydrolyzed species as potential determining, since these minerals do have finite solu-bilities that can amount to significant levels. Silicate minerals, with layered structures, possess a net negativecharge under most natural conditions due to substitutions, for example, Al3+ for Si4+ and Mg2+ for Al3+

in the structure.The surface potential ^ 0 for the above minerals is given by

(16.3-4)

where F is the Faraday constant and a+ and a_ are activities of the positive and negative potential-determining ions with valencies Z+ and Z_ (inclusive of sign); a^ c and a!?c are activities under conditionsof zero charge of the particle surface. Such a condition of zero charge is called the point of zero charge(PZC). Particles will carry a positive charge below the PZC, represented in terms of the negative of thelogarithm of the positive potential-determining ions, and negatively charged above it. Since the system asa 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 resultantdiffuse soluble layer is given in Fig. 16.3-1.

For oxides and salt-type materials, adsorption of both organic and inorganic flotation reagents are oftenthe result of electrostatic attraction between the solid and the reagent. The PZC of the solid is an importantcharacteristic property in such cases and can be determined easily by experiment. Typical PZC values ofsome common minerals are given in Table 16.3-1. It is to be noted that the PZC of the minerals has beenshown, using zeta potential (potential of the shear region) measurements, to be affected significantly byvarious factors such as pretreatment of the solid, extent of aging, storing, as well as the pH and even theionic strength of the solution in which it is stored.45*6870

It has been shown recently that the commonly used cleaning procedures such as leaching in acidic andhot solutions can affect drastically both the sign and magnitude of the experimentally measured parameterssuch as the zeta potential.71'72 In addition to the above mentioned variables, surface chemical heterogeneityof the particles also can contribute significantly to the range of PZC values that can be obtained for a given

An interesting study, in this regard, by Kulkarni and Somasundaran73 involved the analysis of variousspots on a typical hematite particle using scanning electron microscopy, energy dispersive X-ray analysis,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 ofsilica at spots F and G whereas spot H showed almost pure hematite. For this particular sample, whereasthe 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 willdecrease the PZC of the hematite to lower pH values. It is to be noted that, because of the presence ofpositive hematite regions on the mineral, the adsorption of anionic surfactants still can take place abovethe net PZC of the sample. In fact, results from the literature (see Fig. 16.3-3) indicate the adsorption ofanionic surfactants above the net PZC of hematite.74'75 In such cases, the observed adsorption could bedue to the surface chemical heterogeneities rather than any chemisorption of the collector as speculated inthe past.74'75 In addition, chemical heterogeneity of the particles can contribute significantly to the rangeof PZC values that can be obtained for a given solid.

In the case of sulfide minerals, oxidation of the surface also can affect the PZC considerably. As thepH increases, the surface may get oxidized and the potential obtained at any particular pH may be the netvalue 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 athigher pH values. Some of the wide range of values shown in Table 16.3-1, for example, chalcocite,chalcopyrite, pentlandite, and sphalerite, could have resulted partly from such surface oxidation. The roleof the electrical nature of the interface in determining adsorption can be seen for the case of adsorption ofdodecylsulfonate on alumina76 (see Fig. 16.3-4). It can be seen that only below the point of zero chargeof 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 withcationic amine is significant only above the point of zero charge (see Fig. 16.3-5). Indeed, change inelectrical characteristics due to adsorption of inorganic species can affect significantly the flotation responseof the particulates, as will be seen later. Thus, flotation can be depressed by adding electrolytes that willcompete with the flotation reagents for adsorption in the interfacial region or enhanced by adding thoseelectrolytes that can adsorb specifically and change the charge in the desired direction. Depression of amineflotation of quartz using monovalent and divalent inorganic cations has been analyzed recently on the basisof the double-layer model and its compression.77 Toward this purpose we rewrite Eq. (16.3-1) with theAGJj5 consisting of the electrical term and a term to account for the specific adsorption of the bivalent ion

(16.3-5)

where <t> is the specific adsorption energy. Assuming that ^5 is equal to the zeta potential, that the adsorptiondensity of the collector ions at the solid-liquid interface is constant for a given amount of flotation and thatthe addition of electrolytes has no effect on the specific adsorption potential of the collector ions, one canwrite the following equation for the ratio C N , / ^ for equivalent flotation:

(16.3-6)

r*a and Ff0 are, respectively, the adsorption densities of sodium and barium counterions under conditions

SURFACECHARGE STERN

PLANE

SHEARPLANE

POTENTIAL-DETERMINING IONSHYDRATEDCOUNTER IONSNEGATIVE CO-IONS

POTE

NTIA

L

DISTANCEFIGURE 16.3-1 Schematic diagram of the diffusedouble layer—Stern's model.

TABLE 16.3-1 Typical Point of Zero Charge (PZC) Values of Common Minerals

Oxides IEP/PZC pH Reference

Anatase 5.9 8Cassiterite 4.5 9Chromite 5.6-7.2 10, 11Corundum 9-9.4 12, 13Cuprite 7-9.5 14, 15Goethite 6.7 16Hematite (natural) 4.8-6.7 17Hematite (synthetic) 8.6 17Magnesia 12.0 18Magnetite 6.5 19Pyrolusite 5.6,7.4 20Rutile 6.0 21Tenorite 9.5 22

Salt Type IEP/PZC pH Reference

Aragonite 5.0 23Barite, pBa 3.7-7.0 3.4 24Calcite, pCa 3.5, pCO3 3.0 8-10.8 25,26Celestite 2.3 23Dolomite 7.0 27Eggonite 4.0 28Fluorapatite 4.6 29, 30Fluorapatite (synthetic), pCA 4.4, pF 4.6 5.2 31Francolite, pHPO4 3.8-4.9 32Magnesite 6-6.5 27Monazite 3.4 24Scheelite, pCA 4.8 28Silver, pAg 4.1-4.6 28Silver iodide, pAg 5.6 33Silver sulfide, pAg 10.2 34Strengite 2.8 28

Silicates IEP/PZC pH Reference

Andalusite 5.2-7.5 35,36Augite 2.7 37Bentonite 3.0 38Beryl 3.1-4.4 39,40,41Biotite 0.4 41Chrysocolla 2.0 42Garnet 4.4 41Kaolinite 3.4 38Kyanite 6.2-7.9 35, 36,43Muscovite 0.95 44Quartz 2.3-3.7 45,46,47Rhodonite 2.8 42Spodumene 2.5-4 48,49Talc 3.5 51Tourmaline 4.0 52Zircon 5.8 41

Sulfides IEP/PZC pH Ref. Comments

Antimonite 2-3.0 53 Conditioning time not specifiedChalcocite 3-10 54Chalcopyrite 2.0-3.0 55, 56 Conditioning time not specifiedChalcopyrite 5.25, 8.0 57Cinnabar 3.0-4.0 58Galena 2.0-4.0 59

TABLE 16.3-1 {Continued)

Sulfides IEP/PZC pH Ref. Comments

Molybdenite 3.0 60.61Nickel sulfate 2.5-3.0 62Pentlandite 11.5 63Pyrite 6.2-6.9 64 Short conditioning timePyrrhotite 3.0 55 Conditioning time not specifiedSphalerite 2-7.5 51.65 Conditioning time not specified

66, 67

"Any condition corresponding to zero electrokinetic potential is referred to as IEP. In the absence of specificadsorption PZC = IEP

FIGURE 16.3-2 (a) Scanning electron micrograph of a hematite sample on which spot analysis wasconducted, (b) EDAX analysis of spot G shown in part (a). Analysis of spot E was similar to that obtainedfor spot G. (c) EDAX analysis of spot H as shown in part (a). (After Kulkarni and Somasundaran:7*courtesy of Elsevier Seuqoia S.A.. Lausanne, Switzerland.)

FIGURE 16.3-2 (Continued)

FIGURE 16.3-3 Zeta potential of natural hematite in sodium dodecylsulfate solution. (Data from Shergoldand Mellgren.7475)

ZE

TA

PO

TE

NT

IAL

,

FIGURE 16.3-5 Flotation of calcite with dodecylammonium acetate (DDAA) and sodium dodecyl sulfate(DDSO4) solutions. (After Somasundaran and Agar;25 courtesy of Academic Press.)

FLO

ATED

, %

pHFIGURE 16.3-4 Adsorption of dodecylsulfonate on alumina as a function of pH. (After Somasundaranand Fuerstenau;76 courtesy of the American Chemical Society.)

of equivalent flotation and therefore, by assumption, under constant concentration of the collector. c£a andcf* are the corresponding bulk concentrations of sodium and barium ions and ?** and $** are the corre-sponding zeta potentials. rNa and r8* are considered in this case to be the radii of the hydrated sodium andunhydrated barium ions, respectively, and ^8* is the specific adsorption energy of 1 mol of barium ions.The adsorption of hydrated sodium ion on oxide minerals is nonspecific, since its presence is not knownto change the point of zero charge of these minerals. Using a value of 2 for T1^VF8*1 and 3RT for ^8*, weobtain values on the basis of Eq. (16.3-6) for the ratio of c£a cBa for constant flotation. These theoreticalvalues are seen in Table 16.3-2 to be in fair agreement with experimental values. Considering the complex

ELEC

TROP

HORE

TIC M

OBIL

ITY,

micr

ons/

sec

per v

olt/c

mMONOLAYER-

ADSO

RPTIO

N DE

NSIT

Y, p

mol

e/m

2

PZC

OF A

LUM

INA

TABLE 16.3-2 Calculated and Experimental Values for the Relative Effectiveness of Sodium Ionsand Barium Ions in Depressing Quartz Flotation at Natural pH Using 10~4 kmol/m3 perDodecylammonium Acetate

Present£Na $•** Calculated Experimental

Floated (%) cNa (kmol/m3) c** (kmol/m3) (mV) (mV) c^/c** cNa/cBa

90 1 x KT3 2 x 10"5 - 6 3 - 5 0 64 5070 6 x HT3 1.5 X 10"4 - 4 9 - 3 5 33 4050 1.5 x 10"2 8 X 10"4 - 4 0 - 2 2 18 2030 5 x KT2 5 x 10~3 - 3 2 - 1 0 10 10

nature of the flotation process, this agreement must be considered to provide an excellent support for therole of the electrostatic interactions in determining the flotation of such materials.

16.3-2 Chain-Chain Interactions

The zeta potential plot for alumina given in Fig. 16.3-4 as a function of pH of dodecylsulfonate solutionsshows a reversal of slope below about pH 7, suggesting increased adsorption below this pH involvingforces in addition to electrical attraction. The adsorption isotherm obtained for dodecylsulfonate on aluminain fact shows a marked change in slope at a particular surfactant adsorption supporting such an interpretation.Based on the experimental observations that a number of other interfacial properties such as flotation,contact angle, and suspension settling rate undergo a marked change in a given surfactant concentrationrange, it was proposed that at low concentrations of the surfactant, the surfactant ions are adsorbed on themineral due to electrostatic forces, while at high concentrations adsorption is assisted further by forcesarising from lateral associative interactions of the adsorbed surfactant species (see Figs. 16.3-3-16.3-7).The concentration at which such two-dimensional lateral interactions begin has been shown to depend onpH, temperature, and the chemical state and the structure of the surfactant.

EQUILIBRIUM CONCENTRATION, kmol/m?

FIGURE 16.3-6 Adsorption density of dodecylsulfonate, electrophoretic mobility, and settling rate ofalumina-sodium dodecylsulfonate system as a function of the concentration of sodium dodecylsulfonate.78

(Courtesy of Academic Press.)

ADSO

RPTI

ON D

ENSI

TY, m

ol/c

m2

SETT

LING

INDE

X, R

ELAT

IVE

CHAN

GE O

F IN

TENS

ITY

ELEC

TROP

HORE

TICM

OBIL

ITY,

mic

rons

/sec

per

vol

t/cm

FIGURE 16.3-7 Schematic representation of adsorption of a long-chain anionic surfactant: (a) individuallyat low concentrations and (b) with lateral association between chains at higher concentrations.

16.3-3 Covalent Bonding

In contrast to that of adsorption of sulfonates on alumina where electrostatic forces are primarily responsible,the adsorption of fatty acids on solids such as calcite, fluorite, barite, and apatite has been considered tobe the result of covalent bonding of surfactant species to the solid surface species. Such adsorption, usuallyreferred to as chemisorption, first was proposed by French et al.79 for the adsorption of oleate on fluoriteon the basis of results obtained from infrared analysis of the solid surface contacted with the oleate.Subsequently, Peck and Wadsworth80 reported chemisorption of oleate on calcite and barite also. Thechemisorption has been proposed to take place by an ion-exchange mechanism in which the surfactantanions replace an equivalent amount of lattice ions such as F" to form a surface layer of alkaline eartholeate. The ion-exchange mechanism has been confirmed by Bahr et al.81*82 and Bisling83 who obtainedstoichiometric release of fluoride ions into the system during the adsorption of oleate on fluorite. Similarmechanisms resulting in the formation of salts have been proposed by Shergold84 for the adsorption ofdodecylsulfate on fluorite, Cumming and Schulman85 for that of dodecylsulfate on barite, and Fuerstenauand Miller86 for that of alkylsulfonates on calcite.

As indicated above, a technique used for studying adsorption in such systems is the infrared analysisof the surface contacted with the surfactant. In general, use of such spectroscopic techniques and interpre-tation of such results have to be attempted with caution. The preparatory steps for the spectroscopic analysissuch as washing, drying, or any aging conceivably can alter the nature of the surface complexes. In fact,complexes observed during the analysis could have been generated during such preparatory steps.

Also, oleate has been suggested to adsorb on calcite due to electrostatic bonding below its point of zerocharge and covalent bonding above it. Results of oleate adsorption and zeta potential changes supportingsuch a mechanism are given in Figs. 16.3-8 and 16.3-9. The sharp increase in the slope of the adsorptionisotherm is attributed to the precipitation of calcium oleate since, with calcium present at a concentrationof 1.5 X 10~4 kmol/m3, the solubility limit is exceeded for calcium oleate above about 5 x 10~5 kmol/m3 of oleate. Oleate adsorption at concentrations below 10~6 kmol/m3 oleate and at pH values below thePZC of calcite is considered to be due to electrostatic attraction between the negative oleate ions andpositive surface sites, since under these conditions there is very little change in the zeta potential.

16.3-4 Hydrogen Bonding

Surfactants containing phenolic, hydroxyl, carboxyl, and amine groups have been considered to formhydrogen bonds in many systems. For example, adsorption of oleic acid on fluorite and beryl pretreatedwith hydrofluoric acid has been proposed to involve hydrogen bonding.88 According to Parks' review ofGiles' work, adsorption of phenols on alumina and silica and some textile substrates also involves hydrogenbonding. In this regard, the mechanism suggested by Sorensen,89 based on the structural similarity betweenthe crystal and the surfactant, is noteworthy.

SOLUTION

SOLID

SOLUTION

SOLID

SURFACE POTEN-TIAL DETERMININGIONS CO-IONS

COUNTER IONSCOLLECTORCATIONS

SPECIFICALLYADSORBINGDEHYDRATEDCOUNTER IONS

FIGURE 16.3-9 Change in zeta potential of calcite particles as a function of pH at constant ionic strength10"3 kmol/m3 KNO3). (After Somasundaran;87 courtesy of Academic Press.)

A ZE

TA P

OTE

NTIA

L, m

V

O m m

EQUILIBRIUM CONCENTRATION OF OLEATE, kmol/m3

FIGURE 16.3-8 Adsorption isotherm of potassium oleate on calcite at a natural pH of 9.6. (After So-masundaran,87 courtesy of Academic Press.)

OLE

ATE

ADSO

RBED

,

16.3-5 Structural Compatibility

For the case of anionic flotation of simple salts such as fluorite, it has been suggested by Sorensen thathydrogen bonding between the oxygen of the collector and the fluoride species is active and that it isassisted by the electron resonance of the polar groups, the structure of which must be compatible with thegeometry of the mineral crystal. The role of structural compatibility also has been examined for the caseof soluble salts. For example, Fuerstenau and Fuerstenau90 proposed that the surfactant adsorption onsoluble salts is governed by a matching of size of the functional group of the surfactant with that of similarlycharged lattice ions of the solid. Thus, aminium ions adsorb on sylvite (KCl) but not on halite (NaCl),owing to the comparable size of the aminium ion and the potassium ion. It is to be noted, however, thatthis theory fails to explain why a long-chain anionic sulfate will adsorb only on KCl but no on NaCl.

An alternate mechanism in terms of hydration properties of the solid has been put forward by Rogersand Schulman91 for the adsorption of surfactants on soluble salts.

16.3-6 Hydration Factors

According to Rogers and Schulman,91 adsorption on soluble salts is governed by their solvation properties,the ones with the largest negative heat of solution being a better adsorbent than the others. However, thistheory provides no adequate explanation for several adsorption systems involving soluble salts.

16.3-7 Precipitation

An interesting consideration by du Rietz involves a condition of precipitation of the surfactant-lattice ioncomplex for incipient flotation.92 This mechanism has been examined subsequently in detail by a numberof investigators.

16.3-8 Adsorption at Liquid-Air Interface

Even though the flotation process involves three phases and three interfaces, most research work has beensolely on the behavior of the solid-liquid interface. This is in spite of the fact that adsorption at the solid-liquid interface, as shown in Fig. 16.3-10, is of a considerably smaller magnitude than that at the solid-gas or liquid-gas interface.93 It is to be noted that excellent correlation has been obtained recently betweensurfactant adsorption at the liquid-gas interface and flotation for the hematite-oleate system (see Fig. 16.3-11). It is also important to note that the migration of the surfactant at the liquid-gas interface is faster thanits diffusion from bulk to the interface, as least for this system.94 Such a migration at the interface can helptoward faster attainment of required surfactant adsorption density at the solid-gas interface upon the contactof the bubble with the particle.

ADSO

RPTI

ON D

ENSI

TY,

mol

e/cm

2

SOLID-GASLIQUID-GASSOLID-LIQUID

QUARTZ, GLASSNATURAL pHDDAA

CONCENTRATION, kmol/m3

FIGURE 16.3-10 Comparison of adsorption of dodecylammonium acetate at different interfaces. (AfterSomasundaran;93 courtesy of American Institute of Metallurgical Engineers.)

FIGURE 16.3-11 Comparison of flotation properties of 3 x 10~5 kmol/m3 potassium oleate solutionswith final surface pressure at 250C. (After Kulkarni and Somasundaran;94 courtesy of American Instituteof Chemical Engineers.)

16.3-9 Role of lonomolecular Complexes

Studies of the liquid-gas interfacial properties have provided a new insight into the flotation mechanismsby revealing the prominent role of the complexes formed between different surfactant species in flotation.Surfactants such as fatty acids and amines will undergo hydrolysis in water and produce various complexesdepending on the pH of the solution. Thus, oleate will exist in the ionic form in the alkaline pH range, inthe molecular form in the acidic range, and in the ionomolecular complex in the intermediate pH range.

RH = R- + H+

oieic acid oleate

R" + RH = RRH"oleate oleic acid ionomolecular complex

The role of such ionomolecular complexes has been shown to be a potentially important factor in flotation.In fact, the pH of maximum flotation recovery for the hematite-oleate system is found to correspond withthe pH where maximum complex formation 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, thepH of maximum flotation of quartz using amine has been shown to coincide with the pH at which maximumlowering of the adhesive tension of the system and of the surface tension of amine solutions occurs (seeFigs. 16.3-12-16.3-14). This is also the pH region in which stable amine-aminium ion complexes can beexpected- The thermogravimetric analysis results of Kung and Goddard96 have provided some evidence forthe existence of such ionomolecular complexes in the bulk phase also. From these results, the formationof complexes between neutral molecules and ions appears to play an important part in their enhancedadsorption and resultant flotation using them. It must be pointed out that such correlation has not beenobtained during studies using tertiary amines.

Surfa

ce p

ress

ure,

dy

nes/

cm

%

Floa

ted

O O

FIGURE 16-3-13 Adhesion tension of dodecylammonium chloride solution of various concentrations asa function of solution pH. (After Somasundaran;95 courtesy of Elsevier S.A., Lausanne, Switzerland.)

FLOA

TED,

%

FIGURE 16.3-12 Flotation recovery of quartz as a function of solution pH using dodecylammoniumacetate as collector for flotation duration of 5 and 10 s. (After Somasundaran;95 courtesy of Elsevier S.A.,Lausanne, Switzerland.)

DODECYLAMINE HYDROCHLORIDE 4X10" 4 M

SURF

ACE

TENS

ION

, dyn

es/cm

FIGURE 16.3-14 Surface tension of 4 x 10 4 kmol/m3 dodecylamine hydrochloride solution as a functionof pH determined by pendant drop method, measured 15 s after forming drop.95 (After R. W. Smith,personal communication, 1967.)

The mechanism of adsorption of complexes on minerals has not been investigated. It can be noted,however, that the electrostatic factor can be important in this case also, since the complexes like themonomer ions are charged. In addition, increase in the effective size of the species due to complex formationcan be expected to make the surfactant less soluble in water and hence more active.

16.4 FLOTAIDS

In addition to collectors, a number of other chemical additives are used in flotation to aid separation bythis process. They include frothers, activators, depressants, deactivators, flocculants, and dispersants.

16.4-1 Frothers

To produce the desired froth stability, nonionic surfactants, such as the sparingly soluble monohydroxylatedcresols, usually are added, particularly when the collector used is of the short-chain type. The optimumconcentration of the frother in the system is approximately that at which there is a significant change insurface tension with surfactant addition (Fig. 16.4-1). It is possible, even though not proved, that therestoring force that becomes available upon any distention of the bubble to prevent its rupture mightcontribute toward the required froth stability in the flotation cell. Indeed, this is applicable only if thediffusion of the surfactant to the locally extended surface region is not fast enough to reduce the surfacepressure difference between this region and the surrounding surface, before the distention is repaired bysuch pressure difference.

In addition to inducing froth stability, frother species can take part in the overall process of adsorptionon the mineral surface. Like the collector species, the frother species also can be expected to migrate tothe particle-gas interface during the time of contact and assist in establishing the attachment of the bubbleto the particle. Coadsorption of frother along with the collector species2"4 can be favorable for flotation,possibly because the neutral molecules adsorbed between charged collector ions can reduce the repulsionbetween the latter species and thereby enhance the overall surfactant adsorption.

16.4-2 Activators

Activators are used for enhancing flotation of the minerals that may not possess any flotability in theirabsence. Flotation of quartz 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 quartz in the presence of calcium,activation can be attributed to electrostatic adsorption of the calcium ions on the negatively charged quartz

ADHE

SION

TEN

SION

T1

dyne

s/cm GLASS

and thereby providing sites for adsorption of the oleate collector species. Bivalent ions, upon adsorption,can reverse the sign of the stern potential and thus cause adsorption and flotation with collectors that havea charge of the same sign as that of the mineral (see Fig. 16.4-3).

However, sphalerite activation by copper sulfate is the result of adsorption of copper ions on the surfaceof this mineral, due to ion-exchange processes. The effect of activators also can be due to their reactionswith the collectors to form compounds of low-solubility product.7

Another typical example of activation is that of the oxide or carbonate minerals by sodium sulfide. Forexample, in the case of cernisite,8 the following reactions can produce a surface layer of sulfide:

Na2S + H2O - NaSH + NaOH

PbCO3 + 3NaOH ^ H2O + Na2CO3 + NaHPbO2

NaSH + NaHPbO2 - 2NaOH + PbS

Na2S + PbCO3 - Na2CO3 + PbS

The cerrusite surface, which is altered in the above manner, can be floated with xanthate collectors. Incertain cases, on the other hand, it is necessary to remove altered surfaces using acids to obtain flotation(see Fig. 16.4-4). Acids can also enhance flotation possibly by generating microbubbles on the mineralsurface as has been suggested in the case of calcite.9

SURF

ACE

TENS

ION

FROT

HING

CONCENTRATION OF SOLUTE

FIGURE 16.4-1 Diagram illustrating the correlation betweenfroth stability and surface tension lowering due to the additionof a surfactant. (After Cooke;1 courtesy of John Wiley & Sons.)

8 minute float

3 minute float

Rec

over

y, %

33

-go

, (D

(D

?+

(D

(D

-i .

FIGURE 16.4-2 Flotation of pure sphalerite. The granular mineral, 100/150 mesh was floated with xan-thate 0.10 Ib/ton, terpineol, 0.20 lb/ton, sodium carbonate, 2.00 lb/ton, and copper sulfate, as shown.(From Ref. 5; courtesy of McGraw-Hill, New York.)

Ca Concentration (mmol/L)

FIGURE 16.4-3 Effect of amount of Ca2+ in the flotation of quartz by different surfactants (From Ref. 6.)

16.4-3 Depressants

Depressants are organic or inorganic reagents that prevent the collector adsorption on the mineral byinteracting with the mineral 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 isconsidered to be due usually to its depressing effect on quartz present in the pulp and to its ability to controlthe dispersion of the slimes that are present in the pulp. The effectiveness of silicates has been related tothe degree of polymerization that it can undergo under the given conditions.10 The effect of polyvalentcations in the case of flotation of phosphate or calcite, on the other hand, is attributed primarily to collectorprecipitation in the presence of these ions.1112 Polyvalent ions also can prevent collector adsorption bycausing charge reversal of minerals. For example, addition of soluble phosphate can depress flotation ofapatite using oleate (see Fig. 16.4-5).

Organic reagents used as depressants include starch, tannin, quebracho, and dextrin.13 Except for someshort-chain organic acids, these reagents are characterized by their relatively high molecular weight (105-106) and the presence of strongly hydrated polar groups such as —OH, -COOH, - N H 2 , -SO 3 H, and

Flot

ation

reco

very

, %SDS

SDBS

Aerosol OT

HCLH2SO4-

FLO

ATE

D,

%

CONCENTRATION OF ACID,mol/m3

FIGURE 16.4-4 Effect of the type and concentration of mineral acids on the flotation of phosphate-depressed calcite. (After Saleeb and Hanna.6)

2xK)~4M SDBS

(at pH 10.5)

FIGURE 16.4-5 Effect of phosphate species on the flotation of apatite125. K-oleate 2 x 10'6 kmol/m3.

-COH. These reagents can act by mere adsorption on the minerals as well as by causing flocculation ofthe slime that is responsible for excessive collector consumption. Even though such reagents have beenused extensively as modifiers, the actual mechanisms by which they act are not understood totally. Schultzand Cooke14 and Balajee and Iwasaki15 have shown that the adsorption of starch on iron oxide materialsdepends on the type of starch, its preparation, the extent of branching, and so on. Experiments donerecently on the adsorption of starch and oleate in the presence of each other have provided some insightinto the mechanisms involved here (Ref. 16.3-8). It was found that, in this case, the starch does not reduceflotation by inhibiting the adsorption of surfactant on calcite particles. In fact, the adsorption of oleate oncalcite was found to be higher in the presence of starch than otherwise (see Figs. 16.4-6-16.4-8). Similarly,the adsorption of starch also was enhanced by oleate. Depression of mineral flotation obtained under theseconditions suggested that even though the mineral has adsorbed more oleate, it has remained hydrophilic.This unusual phenomenon was ascribed to the formation of the helical-type structure that starch assumesin the presence of hydrophobic materials or in alkaline solutions and to the fact that the interior of thishelix is hydrophobic and the exterior is hydrophilic. It was suggested that the adsorbed oleate is wrappedinside the starch helices. Interactions between the nonpolar surfactant chain and the hydrophobic starchinterior can be expected to produce mutual enhancement of adsorption. The hydrophilic nature of calcitein the presence of starch and oleate results from the fact that the adsorbed oleate is obscured from the bulk

APATITENO PHOSPHATE

HYOROPHOBICITY

OLEATE ADSORBED,

CONCENTRATION OF STARCH, ppmFIGURE 16.4-6 Adsorption density of oleate on calcite at natural pH 9.6-9.8 as a function of starchadded prior to the oleate addition. (After Somasundaran, Ref. 16.3-87; courtesy of Academic Press.)

SODIUM OLEATE CONCENTRATION, kmol/m3

FIGURE 16.4-7 Effect of oleate addition on the adsorption of starch on calcite at various pH values.(After Somasundaran, Ref. 16.3-87; courtesy of Academic Press.)

solution by starch helices with a hydrophilic exterior and from possible masking of the collector adsorbedon the mineral in the normal manner by massive starch species.

Simple organic compounds such as citric acid, tartaric acid, oxalic acid, and EDTA often are used asmodifiers.16 Some of these reagents react by complexing various interfering ions such as calcium that areusually present in the solution.

16.4-4 Deactivators

Deactivators interact with activators to form an inert species and thus prevent activation. An example isthe deactivation of copper in the xanthate flotation of sulfides by cyanides.

16.5 VARIABLES IN FLOTATION

A number of variables are encountered in flotation due to the variations in the raw materials, methods oftheir preparation, reagentizing, and the actual flotation process itself. An understanding of the effect of the

STAR

CH A

DSO

RBED

,/ig/

g O

FCAL

CITE

FLOA

TED,

%

CONCENTRATION OF STARCH, ppmFIGURE 16.4-8 Percent of calcite floated as a function of starch in 10~4 and 10"5 kmol/m3 sodium oleatesolutions. (After Somasundaran, Ref. 16.3-87; courtesy of Academic Press.)

variables can help toward proper control of the flotation for optimum performance. The effects of majorphysical and chemical variables have been reviewed elsewhere.12

The chemical variables that can play a major role include chemical state and structure of the surfactant,including its chain length, concentrations of surfactant, complexing ions, flocculants, and dispersants, pH,ionic strength, and the temperature of the solution. As mentioned earlier, flotation can be expected to bemaximum if the collector is present as ionomolecular complexes. Substitution of hydrogen in the - C H 2 -groups of the long chain with fluorine has been found to produce a significant increase in flotation.3 Ofcourse, flotation is strongly dependent on collector concentration. Rubin et al.4*5 among others have studiedthe dependence of precipitate flotations and ion flotations on the concentration of the collector. While acollector to colligend ratio of 0.2:1 normally is necessary for achieving good flotation of precipitates, theion flotation was found to need much larger quantities. For foam separation techniques, the most suitablesurfactant concentration is the lowest one that provides the desired foaming properties.6"8 Transiency ofthe foam was found desirable for extraction in solutions of low collector concentrations. In froth flotationalso, an excess of collector has sometimes been found to produce reduced extraction.9

Flocculants and polymers can cause an increase or a decrease in flotation depending on the propertiesof the colligens. Thus, while flotation of B cereus and illite with sodium lauryl sulfate can be enhanced byadding alum,1011 that of calcite and apatite using sodium oleate can be depressed totally using starch.

The pH of the solution is an important variable controlling flotation since the pH can affect the electricalproperties of the particle surfaces and its solubility as well as the chemical state of the surfactant. Theeffect of pH due to its role in determining the surface charge of the particles is illustrated in Fig. 16.3-5where only the collector that is charged oppositely to the mineral surface is capable of producing significantflotation. The role of pH in determining the chemical state of oleate and amine and thereby flotation usingthem has been discussed earlier. Maximum flotation was obtained in both cases under pH conditions thatgenerate ionomolecular complexes of the collector.

Ionic strength has a significant role to play in determining the adsorption of collector on the mineral aswell as on the bubble due to both the increased electrical double-layer compression and the increased saltingout of the collector from the aqueous solution with increase in ionic strength. While the effect on the doublelayer will cause a decrease in flotation for systems where electrostatic attraction is a major factor, thesalting unit effect will produce an increase in flotation. When the increase in ionic strength is the result ofa salt containing a bivalent counterion, the depression of flotation is even larger. This larger effect resultsfrom the tendency of the bivalent ions to adsorb strongly and compete with the collector more than themonovalent ions. This effect also can be used to activate the flotation of a particle that has a charge similarto that of a collector (see Fig. 16.4-3). Enough bivalent ions are introduced in this case to cause a particlecharge reversal, thereby making the collector adsorption possible.

The effect of variation in the temperature of the pulp or solution or flotation has not been studied indetail. Elevation in temperature is expected to decrease adsorption of collectors on minerals if the adsorptionis due to physical forces, and to increase adsorption if it is due to chemical forces. An interesting observationin this regard has been the results obtained for the flotation of hematite using oleate under various ionic

Temperature, 0CFIGURE 16.5-1 Conditioning temperature-ionic strength interactions in Hallimond cell flotation of he-matite. (After Kulkarni and Somasundaran.12)

% F

loate

d

TABLE 16.5-1 Industrial Flotation Systems

RemarksModifiersCollectorGangueMinerals

Coal is naturally flotable; themodifiers are for depressing thegangue flotation

Naturally flotable; modifiers are forgangue depression; graphite,being soft, can coat otherminerals and thus causedifficulties

Separation of nonsulfide mineralsfrom sulfide minerals is relativelyeasy; separating sulfides from oneanother needs careful control ofconditions such as pH anddepressant concentration

Separating finely disseminated Cu-Zn sulfide is a problem

PbS is floated first by xanthate bydepressing ZnS by cyanide; laterZnS is activated by Cu2+

Flotation properties of pentlanditeare not well understood;flotability is in betweenchalcopyrite and pyrrhotite

Naturally flotable; since Mo2S issoft, it can coat other mineralsand thus enhance gangue flotation

Quartz is the gangue for otherminerals; it can be floated easilywith amines during the flotationof minerals; sodium silicate canbe used to depress quartz

Sodium silicate, NaCN,SnCl2, KMnO4, starch,dextrin, lime

Sodium silicate, waterglass

Cyanide, caustic soda,lime

Cyanide, Na2S, ZnSO4,lime

Cyanide, CuSO4

Cyanide, lime

Lime, cyanide, Na2S

Kerosene, fuel oil,alcohols

Kerosene

Xanthates,dithiophosphates

Xanthates

Xanthates

Xanthates

Kerosene, fuel oil

Amines, fatty acids (foractivated quartz)

Pyrite, clay, kaoline,shales, quartz, calcite,feldspar

Calcite, clay, quartz

Pyrite, pyrrhotite, othersulfide minerals, quartz

Pyrite, other sulfides

Pyrite

Pyrrhotite, chalcopyrite,other sulfides

Pyrite, chalcopyritegalena, etc.

Usually quartz is thegangue in otherminerals

Coal

Graphite

Copper sulfides,chalcopyrite,chalcocite,bornite,covellite

Cu-Zn sulfides

Pb-Zn sulfides

Pentlandite

Molybdenumsulfide

Quartz

Mica is floated by depressing quartzand feldspar; during second stagefeldspar is floated by depressingquartz with HF

Flotation of hematite using fattyacids around neutral pH andreverse flotation of quartz usingamines

Easily flotable in the acidic range;calcite is usually present as thegangue in other salt-type minerals

Water glass depresses calciteflotation and aluminum saltsincrease the selectivity

Separation of calcareous anddolomitic apatite is still a difficultproblem

Floated in saturated medium;flotation is closely dependent onthe composition of the medium

Same as for halite

Lignin sulfate, Na2CO3,sodium silicate

Starch, dextrin

Water glass, aluminumsalts

Starch, phosphates,inorganic acids

Sodium silicate, starch,dextrin

Water glassPb or Bi salts

Amines

Fatty acids, amines

Fatty acids, amines

Oleic acid

Oleic acid

Fatty acids

Fatty acidsCarboxylic acids

Sodium dodecyl sulfate

Quartz, mica

Quartz

Calcite

Calcite, quartz, dolomite

Quartz, calcite

CalciteClays, sylvite

Clays, halite

Feldspar

Hematite

Calcite

Fluorite

Apatite

Scheelite

BahteHalite

Sylvite

Flotation is a powerful mineral beneficiation tool that has wide potential in effluent treatments in the following industries:22 oil industry, engineering industrywastes, dairy wastes, food industry, textile fiber wastes, cellulose fibers, rubber wastes, asbestos wastes, polymeric wastes, paper industry wastes, dyes,electroplating industry, vegetable wastes, poultry processing wastes

strength conditions. In this case an increase in temperature enhanced flotation but only under low ionicstrength conditions (Fig. 16.5-1). Above an ionic strength of 2 X 10~3 kmol/m3, flotation was found todecrease with an increase in temperature. These temperature-ionic strength interactions are attributed to bethe effect of adsorption of the oleate on the mineral and the salting out of the oleate from the solution. Itis to be noted that the alterations in temperature also can affect the performance of a foam separationtechnique 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 asthe chemical variables listed above, include gas flow rate, bubble size distribution, agitation, feed rate,foam height, and reagent addition modes.

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 paniculate matter that have beenseparated by froth flotation are given in Table 16.5.1.

REFERENCES

Section 16.1

16.1-1 P. Somasundaran, Foam Separation Methods, in E. S. Perry and C. J. Vann Oss (Eds.), Sepa-ration and Purification Methods, Vol. 1, p. 117, Marcel Dekker, New York, 1972.

16.1-2 P. Somasundaran, Separation Using Foaming Techniques, Sep. Sci., 10, 93 (1975).

Section 16.2

16.2-1 C. C. Harris, Flotation Machines in M. C. Fuerstenau (Ed.), Flotation, Vol. 1, p. 753, A. M.Gaudin Memorial International Flotation Symposium. AIME, New York, 1976.

16.2-2 D. W. Fuerstenau, P. H. Metzger, and G. D. Seele, Eng. Min. / . , 158, 93 (1957).16.2-3 M. C. Fuerstenau, Eng. Min. J., 165, 108 (1964).16.2-4 R. D. Kulkarni, "Flotation Properties of Hematite-Oleate System and Their Dependence on the

Interfacial Adsorption,** D. Eng. ScL, 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 Methods, Sep. Sci., 5, 379 (1970).16.2-7 E. J. Mahne and T. A. Pinfold, Precipitate Flotation, J. Appl. Chem., 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, Flotation: Two Fresh Ways to Treat Effluents, 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. ScL Eng., 3, 19 (1971).16.2-12 S. K. Kuzkin and V. P. Nebera, "Synthetic Flocculants 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 Poly aery lamides, Trans. Faraday Soc, 61 , 1026 (1965).16.2-14 A. M. Gaudin and P. Malozemoff, Recovery by Flotation of Mineral Particles of Colloidal Size,

J. Phys. Chem., 37, 597 (1932).

16.2-15 A. D. Read, "Selective Flocculation of Fine Mineral Suspensions," Stevenage, Warren SpringLab. Report LR88 (MST), 1969.

16.2-16 A. D. Read, Selective Flocculation Separation Involving Hematite, Trans. IMM {London), 80,C24 (1971).

16.2-17 I. Iwasaki, W. J. Carlson, Jr., and S. M. Parmerter, The Use of Starches and Starch Derivativesas Depressants, and Flocculants in Iron Ore Beneficiation, Trans. AIME, 244, 88 (1969).

16.2-18 A. D. Read and A. Whitehead, Treatment of Mineral Combinations by Selective Flocculation,Proc. X Int. Min. Proc. Cong., IMM (London). 949 (1974).

16.2-19 M. Carta, G. B. Alsano, C. Deal Fa, M. Ghiani, P. Massacci, and F. Satta, "Investigations onBeneficiation of Ultrafine Fluorite from Latium," Proc. XI Int. Min. Proc. Cong., Paper 41,1975.

16.2-20 Y. S. Kim and H. Zeitlin, Anal. Chem. Acta, 46, 1 (1969).16.2-21 H. M. Smith and I. E. Puddington, Spherical Agglomeration of BaSO4, Can. J. Chem., 38,

1911 (1960).

16.2-22 J. R. Famard, F. W. Meadow, P. Tymchuk, and I. E. Puddington, Application of SphericalAgglomeration to the Fractionation of Sn-Containing Ore, Can. Metall. Q., 3, 123 (1964).

Section 16.3

16.3-1 M. C. Fuerstenau, Flotation, A. M. Gaudin Memorial VoIs. 1 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, South African Institute of Mining and Metallurgy, Johan-

nesburg, 1982.16.3-4 D. W. Fuerstenau, Froth Flotation, 50th Ann. Vol. AIME, New York, 1962.16.3-5 P. Somasundaran and R. B. Grieves, Interfacial Phenomena of Paniculate/Solution/Gas 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 Flotation, Theory and Applications, Marcel Dekker, NewYork, 1983.

16.3-7 P. Somasundaran, T. W. Healy, and D. W. Fuerstenau, Surfactant Adsorption at the SfL Inter-face—Dependence of Mechanism on Chain Length, / . Phys. Chem., 68, 3562 (1964).

16.3-8 Y. G. Berube and P. L. de Bruyn, Adsorption at the Rutile-Solution Interface, J. Colloid InterfaceScL, 27, 305(1968).

16.3-9 P. G. Johansen and A. S. Buchanan, An Application of the Micro-electrophoresis Method to theStudy of Surface Properties of Insoluble Oxides, Austr. J. Chem., 10, 398 (1957).

16.3-10 B. R. Palmer, M. C. Fuerstenau, and F. F. Apian, Mechanisms Involved in the Flotation ofOxides and Silicates with Anionic Collectors: Part II, Trans. A/ME, 258, 261 (1975).

16.3-11 J. Laskowski and S. Sobieraj, Zero Points of Charge of Spinel Minerals, Inst. Min. Met., 28,C163 (1969).

16.3-12 M. C. Fuerstenau, D. A. Elgillani, and J. D. Miller, Trans. AIME, 247, 11 (1970).16.3-13 D. W. Fuerstenau and H. J. Modi, Streaming of Potentials of Corundum in Aqueous Organic

Electrolyte Solutions, J. Electrochem. Soc, 106, 336 (1959).16.3-14 G. A. Parks, Isoelectric Points of Solid Oxides, Solid Hydroxides and Aqueous Hydroxo-complex

Systems, Chem. Rev., 65, 177 (1965).

16.3-15 D. R. Nagaraj and P. Somasundaran, unpublished results.16.3-16 I. Iwasaki, S. R. B. Cooke, and A. F. Colombo, Flotation Characteristics of Goethite, U.S. Bur.

Mines, Rep. Invest., No. 5593 (1960).16.3-17 D. W. Fuerstenau, Interfacial Processes in Mineral/Water Systems, Pure Appl. Chem., 24, 135

(1970).16.3-18 M. Robinson, J. A. Pask, and D. W. Fuerstenau, Surface Charge OfAl2O3 and MgO in Aqueous

Media, J. Am. Chem. Soc, 47, 516 (1964).16.3-19 I. Iwasaki, S. R. B. Cooke, and Y. S. Kim, Surface Properties and Flotation Characteristics of

magnetite, Trans. AIME, 223, 113 (1962).16.3-20 M. C. Fuerstenau and D. A. Rice, Trans. AIME, 241, 453 (1968).16.3-21 Y. G. Berube and P. L. Bruyn, Electroanal. Chem. Interface Electrochem., 37, 99 (1972).16.3-22 W. Stumm and J. J. Morgan, Aquatic Chemistry, Wiley, New York, 1970.16.3-23 P. Ney, Zeta Potential and Flotability of Minerals, in V. D. Frechette et al. (Eds.), Applied

Mineralogy, Vol. 6, Springer Verlag, Wien, 1973 (German text).16.3-24 G. A. Parks, Aqueous Surface Chemistry of Oxides and Complex Oxide Minerals, Adv. Chem.

Ser. 6, 121 (1967).16.3-25 P. Somasundaran and G. E. Agar, The Zero Point of Charge of Calcite, J. Colloid Interface

ScL, 24, 433 (1967).

16.3-26 M. C. Fuerstenau, G. Gutierrez, and D. A. Elgillani, The Influence of Sodium Silicate in Non-metallic Flotation Systems, Trans. AIME, 241, 319 (1968).

16.3-27 J. J. Predali and J. M. Cases, Zeta Potential of Magnesium Carbonate in Inorganic Electrolytes,J. Colloid Interface ScL, 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. Somasundaran, Zeta Potential of Apatite in Aqueous Solutions and Its Change During Equi-libration, J. Colloid Interface ScL, 27, 659 (1968).

16.3-30 P. Somasundaran and G. E. Agar, Further Streaming Potential Studies on Apatite in InorganicElectrolytes, Trans. SMEIAlME, ISl, 348 (1972).

16.3-31 F. Z. Saleeb and P. L. Bruyn, Surface Properties of Alkaline Earth Apatites, Electroanal. Chem.Interface Electrochem., 37, 99 (1972).

16.3-32 M. S. Smani, J. M. Cases, and P. Blazy, Beneficiation of Sedimentary Moroccan PhosphateOres—Part I: Electrochemical Properties of Some Minerals of the Apatite Group; Part II: Elec-trochemical Phenomena at the Calcite/Aqueous Interface, Trans. SME/AJME, 258, 168 (1975).

16.3-33 J. Th. G. Overbeek, in H. R. Kruft (Ed.) Electrokinetic Phenomena in Colloid Science, Vol. 1,Elsevier, New York, 1952.

16.3-34 W. L. Freyberger and P. L. de Bruyn, Electrochemical Double Layer on Ag2S, / . Phys. Chem.,63, 1475 (1957).

16.3-35 H. S. Choi and J. H. Oh, Surface Properties and Flotability of Kyanite and Andalusite, J. lnst.

Min. Metall.,Jpn., 81, 614 (1965).16.3-36 T. J. Smolik, X. Harman, and D. W. Fuerstenau, Surface Characteristics and Flotation Behavior

of Aluminosilicates, Trans. A/ME, 235, 367 (1966).16.3-37 M. C. Fuerstenau, B. R. Palmer, and G. B. Gutierrez, Mechanisms of Flotation of Selected Iron

Bearing Silicates, Trans. SME/AlME, to appear.16.3-38 I. Iwasaki, S. R. B. Cooke, D. H. Harraway, and H. S. Choi, Fe-Wash Ore Slimes—Mineral-

ogical and Flotation Characteristics, Trans. AIME,, 223, 97 (1962).16.3-39 R. W. Smith and N. Trivedi, Variation of PZC of Oxide Minerals as a Function of Aging Time

in Water, Trans. AIME, 255, 73 (1974).

16.3-40 M. C. Fuerstenau, D. A. Rice, P. Somasundaran, and D. W. Fuerstenau, Metal Ion Hydrolysis

and Surface Charge in Beryl Flotation, Bull. lnst. Min. Met. London, No. 701, 381 (1965).16.3-41 J. M. Cases, Normal Interaction Between Adsorbed Species and Adsorbing Surface, Trans.

A/ME, 247, 123 (1970).16.3-42 B. R. Palmer, G. B. Gutierrez, and M. C. Fuerstenau, Mechanisms Involved in the Flotation of

Oxides and Silicates with Anionic Collectors: Part I, Trans. A/ME, 258, 257 (1975).16.3-43 J. M. Cases, Zero Point of Charge and Structure of Silicates, J. Chim. Phys. Phys. Chim. BioL,

66, 1602 (1969).16.3-45 R. D. Kulkarni and P. Somasundaran, Effect of Aging on the Electrokinetic Properties of Quartz

in Aqueous Solutions, in Oxide Electrolyte /nterfaces, p. 31, American Electrochemical Society,1972.

16.3-46 A. M. Gaudin and D. W. Fuerstenau, Quartz Flotation with Anionic Collectors, Trans. A/ME,2QfI, 66 (1955).

16.3-47 I. Iwasaki, S. R. B. Cooke, and H. S. Choi, Flotation Characteristics of Hematite, Geothite andActivated Quartz with C-18 Aliphatic Acids and Related Compounds, Trans. A/ME, 220, 394(1961).

16.3-48 R. A. Deju and R. B. Bhappu, A Chemical Interpretation of Surface Phenomena in SilicateMinerals, Trans. A/ME, 235, 329 (1966).

16.3-49 A. N. Dolzhenkova, Determination of the Electrokinetic Potential Applicable to Flotation Pro-cesses, Obogashch Rud, 12, 59 (1967).

16.3-50 Y. Y. A. Azim, The Effect of Fluoride on the Flotation of Non-sulfide Minerals, Part II, ZetaPotential Measurements, Stevenage: Warren Spring Lab., ref. R.R./MP/137, 9, 1964.

16.3-51 O. Huber and J. Weigl, Influence of the Electrokinetic Charge of Inorganic Fillers on DifferentProcesses of Paper Making, Wochenbl. Papierfabr, 97, 359 (1969).

16.3-52 D. A. Rice, D. Sci. Thesis, Colorado School of Mines, 1968.16.3-53 B. V. Derjaguin and N. D. Shukakidse, Dependence of the Flotability of Antimonite on the

Value of the Zeta Potential, Trans. /MM, 70, 564 (1960-61).16.3-54 C. A. Ostreicher and D. W. McGlashan, "Surface Oxidation of Chalcocite," Paper presented

at the Annual AIME Meeting, San Francisco, 1972.16.3-55 P. Ney, Zetapotential und Flotierbarkeit von Mineralen, Springer-Verlag, Vienna, 1973.16.3-56 D. McGlashan, A. Rovig, and D. Podobnik, "Assessment of Interfacial Reactions of Chalco-

pyrite, Trans. A/ME, 244, 446 (1969).16.3-57 G. C. Sresty and P. Somasundaran, unpublished results.16.3-58 R. O. James and G. A. Parks, Adsorption of Zn (II) at the Hgs (Cinnabar)-Water Interface,

A/ChESymp. Ser. No. 150, 71, 157 (1975).16.3-59 P. C. Neville and R. J. Hunter, "The Control of Slime Coatings in Mineral Processing," paper

presented at the 4th RACL Electrochemistry Conference Adelaide, 1976.16.3-60 S. Chander and D. W. Fuerstenau, On the Natural Flotability of Molybdenite, Trans. A/ME,252, 62 (1972).

16.3-61 J. M. Wie and D. W. Fuerstenau, The Effect of Dextrin on Surface Properties and the Flotationsof Molybdenite, Int. J. Miner. Proc, 1, 17 (1974).

16.3-62 M. S. Moignard, D. R. Dixon, and T. W. Healy, Electrokinetic Properties of the Zinc andNickel Sulfide-Water Interfaces, Proc. Austr. IMM, 263, 29 (1977).

16.3-63 S. Ramachandran and P. Somasundaran, unpublished results.16.3-64 M. C. Fuerstenau, M. C. Kuhan and D. Elgiilani, Role of Dixanthogen in Xanthate Flotation

of Pyrite, Trans. AIME9 241, 148 (1968).16.3-65 H. A. Bull, B. S. Ellegson, and N. W. Taylor, Electrokinetic Potentials and Mineral Flotation,

J. Phys. Chem., 38, 401 (1934).16.3-66 D. McGlashan, A. Rovig, and D. Podobnik, * * Assessment of Interfacial Reactions of Sulfide

Copper, Lead and Zinc Minerals," paper presented at the AIME Annual Meeting, New York,1968.

16.3-67 M. Bender and H. Mouquin, Brownian Motion and Electrical Effects, J. Phys. Chem., 56, 272(1952).

16.3-68 P. Somasundaran, Pre-treatment of Mineral Surfaces and Its Effect on Their Properties, in CleanSurfaces: Their Characterization for Interfacial Studies, p. 285, Marcel Dekker, New York,1970.

16.3-69 R. W. Smith and N. Trivedi, Variation of Zero Charge of Oxide Mineral as a Function of AgingTime in Water, Trans. AIME', 256, 69 (1974).

16.3-70 G. A. Parks, Am. Mineralogist, 57, 1163 (1972).16.3-71 R. D. Kulkarni and P. Somasundaran, paper presented at 164th meeting of American Chemical

Society, New York, 1972.16.3-72 P. Somasundaran and R. D. Kulkami, New Streaming Potential Apparatus and Study of Tem-

perature Using It, J. Colloid Interface ScL, 45, 591 (1973).16.3-73 R. D. Kulkarni and P. Somasundaran, Mineralogical Heterogeneity of Ore Particles and Its Effect

on Their Interfacial Characteristics, Powder TechnoL, 14, 279 (1976).16.3-74 H. L. Shergold and O. Mellgren, Concentration of Minerals at the Oil-Water Interfaces: He-

matite-Iso-octane-Water Systems in the Presence of Sodium Sulfate, Trans. IMM, 78, C121(1969).

16.3-75 D. W. Fuerstenau, The Adsorption of Surfactants at Solid-Water Interfaces, in M. L. Hair (Ed.),The Chemistry ofBiosurfaces, Vol. 1, p. 143, Marcel Dekker, New York, 1971.

16.3-76 P. Somasundaran and D. W. Fuerstenau, Mechanisms of Alkyl Sulfonate Adsorption at theAlumina-Water Interface, J. Phys. Chem., 70, 90 (1966).

16.3-77 P. Somasundaran, Cationic Depression of Amine Flotation of Quartz, Trans. AIME, 255, 64(1974).

16.3-78 P. Somasundaran, Ph.D. Thesis, University of California, Berkeley, 1964.16.3-79 R. O. French, M. E. Wadsworth, M. A. Cook, and I. P. Cutler, Applications of Infrared

Spectroscopy to Studies in Surface Chemistry, J. Phys. Chem., 58, 805 (1954).16.3-80 A. S. Peck and M. E. Wadsworth, Infrared Studies of Oleic Acid and Sodium Oleate Adsorption

on Fluorite, Barite, and Calcite, U.S. Bur. Mines, Rep. Invest., No. 6202, 188 (1963).16.3-81 A. Bahr, "The Influence of Some Electrolytes on the Flotation of Fluorite by Na-Oleate,"

Dissertation, T. H. Clausthal, CIausthal, 1966.16.3-82 A. Bahr, M. Clement, and H. Surmatz, On the Effect of Inorganic and Organic Substances on

the Flotation of Some Non-sulphide Minerals by Using Fatty Acid Type Collectors, Proc. 8thInt. Min. Proc. Cong., S-Il, 12 (1968).

16.3-83 U. Bisling, "The Mutual Interaction of the Minerals During Flotation, for Example, the Flotationof CaF2 and Ba SO4 ," Dissertation Bergakademie Freiberg, 1969 (German text).

16.3-84 H. L. Shergold, Infrared Study of Adsorption of Sodium Dodecylsulfate by CaF2, Trans. Inst.

Min. Met. Sec. C, 81, 148 (1972).16.3-85 B. D. Cumming and J. H. Schulman, Two Layer Adsorption of Dodecylsulfate on Barium Sulfate,

Aust. J. Chem., 12, 413 (1959).16.3-86 M. C. Fuerstenau and D. J. Miller, The Role of Hydrocarbon Chain in Anionic Flotation of

Calcite, Trans. AIME, 238, 153 (1967).16.3-87 P. Somasundaran, Adsorption of Starch and Oleate and Interaction Between Them on Calcite in

Aqueous Solutions, J. Colloid Interface ScL, 31, 557 (1969).16.3-88 A. S. Peck and M. E. Wadsworth, Infrared Studies of the Effect of Fluorite, Sulfate and Chloride

on Chemisorption of Oleate on Fluorite and Barite, in N. Arbiter (Ed.), Proceedings of the 7thInternational Mining Procedures Congress, p. 259, Gordon and Beach, New York, 1965.

16.3-89 E. Sorensen, On the Adsorption of Some Anionic Collectors on Fluoride Minerals, J. ColloidInterface ScL, 45, 601 (1973).

16.3-90 D. W. Fuerstenau and M. C. Fuerstenau, Ionic Size in Flotation Collection of Alkali Halides,Trans. AIME, 204, 302 (1956).

16.3-91 J. Rogers and J. H. Schulman, Mechanism of the Selective Flotation of Soluble Salts in SaturatedSolutions, in Proceedings of the 2nd International Congress on Surface Activity, p. 243, Vol.Ill, Butterworths, London, 1957.

16.3-92 C. du Rietz, Fatty Acids in Flotation, progress in Mineral Dressing, in Transactions of the 4thInternational Mineral Dressing Congress, p. 417, Almqvist & Wiksells, Stockholm, 1958.

16.3-93 P. Somasundaran, The Relationship Between Adsorption at Different Interfaces and FlotationBehavior, Trans. SMEIAIME, 241, 105 (1968).

16.3-94 R. D. Kulkarni and P. Somasundaran, Kinetics of Oleate Adsorption at the Liquid/Air Interfaceand Its Role in Hematite Flotation, in P. Somasundaran and R. B. Grieves (Eds.), Advances inInterfacial Phenomena on Paniculate Solution, Gas Systems, Applications to Flotation Research,AIChE Symposium, Series No. 150, p. 124, AIChE, New York, 1975.

16.3-95 P. Somasundaran, The Role of Ionomolecular 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., 232, 812(1969).

Section 16.4

16.4-1 S. R. B. Cooke, in H. Mark and E. J. W. Verwey (Eds.), Advances in Colloid ScL, Vol. Ill,

Interscience, New York, 1950.16.4-2 J. H. Schulman and J. Leja, Molecular Interactions at the Solid-Liquid Interface with Special

Reference to Flotation at Solid-Particle Stabilized Emulsions, Kolloid-Z., 136, 107 (1954).16.4-3 J. Leja, Proc. 2nd Int. Conf Surface Activity, London, 3, 273 (1957).16.4-4 J. H. Schulman and J. Leja, in J. F. Danielli et al. (Eds.), Surface Phenomena in Chemistry and

Biology, p. 236, Pergamon, New York, 1958.16.4-5 A. M. Gaudin, Flotation, 2nd ed., pp. 310-314, McGraw-Hill, New York, 1957.16.4-6 F. Z. Saleeb and H. S. Hanna, Flotation of Calcite and Quartz with Anionic Collectors, the

Depressing of Activating Action of Polyvalent Ions, J. Chem. U.A.R. (Egypt), 12, 237 (1969).16.4-7 M. C. Fuerstenau, The Role of Metal Ion Hydrolysis in Oxide and Silicate Flotation Systems,

AIChE Symp. Ser., No. 150, 71 (1975).16.4-8 V. A. Glembotskii, V. I. Klassen, and I. N. Plaskin, Flotation, translated by R. E. Hammond,

Primary sources, New York, 1972.16.4-9 A. K. Biswas, Role OfCO2 in the Flotation of Carbonate Minerals, Indian J. Tech., S9 187

(1967).

16.4-10 A. S. Joy and A. J. Robinson, in J. F. Danielli, K. G. A. Pankhurst, and A. C. Riddiford (Eds.),Flotation, Recent Progress in Surface 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 Florida Leached ZonePhosphates Ore with Fatty Acids, Trans. AIME, 208, 70 (1957).

16.4-12 K. P. Ananthapadmanabhan, "Effects of Dissolved Species on the Flotation Properties of Calciteand 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 Mineralsin Flotation, A. M. Gaudin Memorial Volume, AIME, New York, 1976.

16.4-14 N. F. Schultz and S. R. B. Cooke, Froth Flotation of Iron Ores, Ind. Eng. Chem., 45, 2767(1953).

16.4-15 S. R. Balajee and I. Iwasaki, Adsorption Mechanisms of Starches in Flotation and Flocculationof Iron Ores, Trans. AIME, 244, 401 (1969).

16.4-16 F. F. Apian and D. W. Fuerstenau, Principles of Non-Metallic Mineral Flotation, in D. W.Fuerstenau (Ed.), Froth Flotation, 50th Ann. Vol., AIME, New York, 1962.

Section 16.516.5-1 P. Somasundaran, Interfacial Chemistry of Paniculate Flotation, 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. 150, p. 1, AIChE, New York,1975.

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 Volume, AIME, New York, 1976.

16.5-3 P. Somasundaran and R. D. Kulkarni, Effect of Chainlength of Perfluoro Surfactants as Collec-tors, Trans. IMM, 82, cl64 (1973).

16.5-4 A. J. Rubin, J. D. Johnson and C. Lamb, Comparison of Variables in Ion and PrecipitateFlotation, lnd. Eng. Chem. Proc. Des. Dev., 5, 368 (1966).

16.5-5 A. J. Rubin and W. L. Lapp, Foam Fractionation and Precipitate Flotation, Sep. ScL, 6, 357(1971).

16.5-6 R. W. Schneff, E. L. Gaden, E. Microcznik, and E. Schonfeld, Foam Fractionation, Chem.Eng. Prog., 55, 42 (1959).

16.5-7 H. M. Schoen, E. Rubin, and D. Ghosh, Radium Removal from Uranium Mill Waste Water, J.Water Pollut. Contr. Fed., 34, 1026 (1962).

16.5-8 R. B. Grieves, Foam Separation for Industrial Wastes: Process Selection, J. Water PollutionControl Federation 42, R336, 1970.

16.5-9 P. Somasundaran and B. M. Moudgil, The Effect of Dissolved Hydrocarbon Gases in SurfactantSolutions on Froth Flotation of Minerals, J. Colloid Interface ScL, 47, 290 (1974).

16.5-10 A. J. Rubin, in Adsorptive Bubble Separation Techniques, p. 216, Academic, New York, 1972.16.5-11 R. B. Grieves and D. Bhattacharya, Foam Separation of Complexed Cyanide, J. Appl. Chem.,

19, 115(1969).16.5-12 R. D. Kulkarni and P. Somasundaran, Effects of Reagentizing Temperature and Ionic Strength

and Their Interactions in Hematite Flotation, Trans. SME, 262, 120-125 (1977).16.5-13 E. Rubin and E. J. Gaden, Jr., Foam Separation, in H. M. Schoen (Ed.), New Chemical Engi-

neering Separation and Techniques, Interscience, New York, 1962.16.5-14 R. Lemlich, Principles of Foam Fractionation, in E. S. Perry (Ed.), Progress in Separation and

Purification, Vol. 1, p. 1, Interscience, New York, 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 Effluent Streams, in J. O'M. Bockris

(Ed.), Electrochemistry of a Cleaner Environment, 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 Flotation,*' Denver Bull., F10-B16.16.5-19 N. H. Grace, G. J. Klassen, and R. W. Watson, Denver Bull., F10-B21.16.5-20 C. A. Roe, "Froth Flotation, Industrial and Chemical Application," Denver Bull., F10-B46.16.5-21 J. W. Jelks, "Flotation Opens New Horizons in the Paper Industry," Denver Bull., F10-B64.16.5-22 S. H. Hopper and M. C. McCowen, 44A Flotation Process for Water Purification," Denver Bull.,

F10-B71.