Colloids and Surfaces, 13 (1985) 73-85Elsevier Science Publishers B. V ., Amsterdam

73Printed in The Netherlands

A STUDY OF POLYMER/SURF ACT ANT INTERACTION AT THEMINERAL/SOLUTION INTERFACE

P. SOMASUNDARAN and J. CLEVERDON

School of Engineerinl and Applied Science. Columbia Uniuersity, New York.NY 10027 (U.S.A.)

(Received 4 October 1983; accepted in final form 18 April 1984)

ABSTRACT

Interaction between a cationic polymer (acrylamidemethacrylamidopropyltrimethyl-ammonium chloride copolymer) and cationic and anionic surfactants (dodecylammoniumchloride and dodecylsulfonate) on quartz is studied using adsorption, electrokinetic andflotation techniques. At pH 6.5, the polymer depresses amine flotation of quartz butwithout depressing amine adsorption on it. E]ectrokinetic experiments yielded zeta-potentia] values characteristic of the polymer as long as polymer ia adsorbed irreapectiveof both amine adsorption and original potentia] of quartz.

Around pH 10 where amine is most surface active, polymer adsorption from a solutioncontaining both the polymer and amine is negligible. Furthermore, at this pH any pread-sorbed polymer is displaced from the surface upon subsequent addition of amine.

A molecular model is proposed for the polymer-surfactant layer on the quartz par-tic]e with the massive polymer species masking the adsorbed amine, to account for thehydrophilic characteristics of the particle. In accord with this model, quartz is activatedby the adsorbed cationic polymer for flotation by the anionic sulfonate.

INTRODUCTION

In many industrial processes, such as flotation and enhanced oil recovery,polymers are now used along with surfactants. Flocculation followed byflotation of iron ore is a recent example of such a process [1, 2]. In addi-tion, nowadays polymers very often are added either to aid filtration, toclean effluents or as grinding aids. These reagents can markedly affect otherdownstream processes such as flotation [3-10]. In such operations, selec-tivity can be affected through interactions between polymer and surfactantin the bulk or at the solid/liquid or liquid/gas interface. At the solid/liquidinterface, not only the amount of each reagent adsorbed but also the manner(orientation) of adsorption has an important effect on the process. However,to the authors' knowledge, no precise information on these factors exists inthe literature, although there have been a few reports on interactions in bulksolutions [11-24]. Recent work [11] on such solution properties as relativeviscosity, conductivity, and surface tension with various nonionic, anionicand cationic polyacrylamides and sodium dodecylsulfonate or dodecylamine

0166-6622/85/S03.30 C> 1985 Elsevier Science Publiahers B. V.

74

hydrochloride showed measurable interaction effects but only in the case ofthe oppositely charged polymer and surfactant systems. Also depending onthe ionic natures of the polymer and surfactant they can precipitate, and insome cases the precipitate thus formed can dissolve upon increasing the sur-factant concentration. This redissolution was considered to occur throughcomplexation. It was noted that the observed effects can affect the adsorp-tion behavior of different species at the solid/liquid interface and thereby in-fluence processes such as flocculation, flotation and micellar flooding.

In this work, interactions of a cationic polymer, and anionic and cationicsurfactants at the quartz/aqueous solution interface are examined using ad-sorption and electrokinetic techniques together with flotation. Clearly seenis the power of the use of the electrokinetic technique in conjunction withother techniques in deriving information on the possible arrangement of ad-sorbed species at the interface.

EXPERIMENTAL

Materials

High purity crystalline quartz (Arkansas) purchased from Ward's NaturalSciences Establishment was crushed and ground in a stainless-steel ball mill;the -20-lJ.m fraction was cleaned by boiling in HCI solution and repeatedrinsing with water, freeze-dried and stored till use. The average particle sizeas measured using a Fisher subsieve sizer was 6 IJ.m. For flotation experi-ments, -590 to +210-lJ.m fraction of quartz was used after cleaning with amagnetic separator and leaching with warm nitric acid.

The cationic copolymer P AMA used in this study was prepared from 14C-labeled acrylamide and methacrylamidopropylltrimethylammonium chlorideby irradiating them in acetone-water solution using 6°Co source at 6 kradsh -I for 18 h. Unreacted monomer was removed by repeated washing withacetone and the sample was freeze-dried and stored till use. The molecularweight was estimated from intrinsic-viscosity data to be 0.8 X 106.

Dodecylammonium chloride and sodium dodecylsulfonate purchasedfrom Eastman Kodak Co. and Aldrich Chemical Co., respectively, were usedas collectors without further purification.

Procedure

For adsorption tests, 2 g of the - 20-JJm quartz were conditioned first fortwo hours on a wrist-action shaker in 10 ml of NaC! solution adjusted to thedesired pH, and then for another six hours after adding 10 ml of the polymersolution. (Equilibrium was attained within this interval at all pH levels, Fig.1). The pH was then measured, the sample was centrifuged and the residualpolymer concentration was determined using a liquid scintillation counter.Adsorption of amine was determined by titration against a known concentra-

ntion of sodium dodecylsulfonate using a two-phase technique [25]. Todetermine the extent of polymer desorption, after centrifugation 10 ml ofthe supernatant were replaced with 10 ml of NaCl solution, and the sampleagitated for another six hours.

pH . 10.4 j; 0.401.2

0"0E. 1.0

zQl-e.~ 0.8'"~ 0.61

c 0

I . 3 I 10-2 kmo' 1m3 HoC'T . 24 t 1- C

SIL. . 10 %CO~C. POL. YME R . 260 IIIQ/kQ

6.0 t; 0.& (natural)

0.4 t; 0.1 £).

0.2

0.8.. .. 10 12 14 It.

TIM!. hour..

Fig. 1. Adsorption of P AMA on quartz as a function of time.

For zeta-potential measurements, 0.02 g of quartz was conditioned in 40ml of total solution in the same manner as in the adsorption experiments.Polymer-adsorption data in these cases was simultaneously determined bycentrifuging the samples after zeta-potential measurements and analyzingthe supernatant for residual polymer concentrations.

For flotation, 1 g of the -590 to +210ilm quartz was conditioned withthe necessary reagents on a tumbler at 16 rpm for 10 min and then floatedin a modified Hallimond tube for 15 s using nitrogen at a glas-flow rate of36cm3min-1 [3].

RESULTS AND DISCUSSION

PAMA adsorption

The extent of adsorption on P AMA on quartz was first determined undernatural pH conditions (pH 6.3 j; 0.6). Figure 2 shows measurable adsorptionat concentrations as low as 1 mg per kg. Adsorption appears to reach a pla-teau at about 500 mg per kg. The results of dilution tests show that adsorp-tion of P AMA is essentially irreversible by dilution under the conditions usedhere. Furthermore, it is seen that, while equilibrium was possibly attainedwithin the six hours of conditioning below 100 mg per kg, above this con-centration adsorption continues to take place even after dilution.

76

~...~E

z

2...Go~0III0C

01 1.0 10 100

RESIDUAL CONCENTRATION, "'v/kv

Fig. 2. Adsorption isotherm of PAM A on quartz under natural pH conditions.

Quartz flotation in amine and PAMA solutions

The effect of polymer addition on quartz flotation using amine was testedat two different amine levels. Results given in Fig. 3 show that completedepression of flotation is achieved at 1 mg per kg polymer. In order to deter-mine whether or not this depression of hydrophobicity is due to reduced ad-sorption of amine (the traditional explanation), adsorption of amine onquartz was determined in the presence and absence of the polymer. The re-sults are tabulated inside Fig. 3. Most interestingly, the presence of the poly-mer resulted in decreased flotation without any significant effect on thesurfactant adsorption. We have made similar observations for the calcite-oleate system using starch as depressant [26].

100QUARTZ/AMINE/PAMA

AMINE (kmol/m")

0 36.10'0

t. 84.10-0pH. 65

80

Q'" 60...40-'...

.t 40\.

Effect of POlyme' onAmIne Adscrptlon(C, E 63x'O"kmO:/",3)

\\, Polymer,

. mQ/kQ ~ 500,20

46144~

0:0 I 10 100

POLY~ER CONCENTRATION. m9/k9

Fie. 3. Depreuion of notation of quartz using dodecylamine by the cationic polymerP AMA at natural pH. Adsorption of amine in the pre-nce and absence of the polymer isshown in the inset.

77

Zeta potential in amine solutions

To obtain additional information about the nature of the mineral surfaceunder these conditions, the zeta potential of the -20-p.m quartz particleswas determined together with polymer adsorption, at different polymer andamine concentrations, as a function of pH. Ionic strength was maintained at3 X 10-2 kmol m-3 using NaCI for all tests. Figure 4 shows the pH dependen-ce of quartz zeta potential in 3 X 10-2 klnol m-3 NaCI and 5 X 10-4 kmolm-3 amine plus 3 X 10-2 kmol m-3 NaCI solutions. An isoelectric point ofabout pH 3.0 is obtained for quartz, in agreement with literature valueswhich vary from 1 to 3.7 [27]. The presence of amine is found to have a sig-nificant effect on zeta potential with charge reversal in a narrow pH regionaround 10. Notably, this is also the pH region in which the highest quartzflotation is usually obtained [28]. This phenomenon has been explainedby taking into account the formation of the highly surface-active amine-aminium complex in this pH range (see Fig. 5). At higher pH values mostof the amine is in the neutral form which does not lend itself to adsorption[29] .

Fig. 4. Zeta potential of quartz in water and in dodecylamine solution as a function ofpH, both under constant ionic-strength conditions.

78

~-DDDECYLAMINE HYDROCHLORIDEC . ~'10-4kmOl/m3

2 8

pH,0

RNH; ~ RNH2 + H+ pKa . 10.63

2RNH; ~ (RNH3)~+ pKO . -2.08

RNH; + RNH2 ~ (RNH2RNH3)+ pKAO' - 3.12

RNH2(.(J ~ RNH2(aq,) PKS' 4.69

CT . CR"M + CRuM- + 2t"-RNM I'. + 2C(~"M RNM I., ~ 3 , 32 2 3

Fig. 5. Dodecylamine species diagram as a function of pH for a total amine concentrationof 5 X lO--kmol mos.

Zeta potential in polymer solutions and polymer adsorption

Zeta potential of quartz particles at 0.1, 0.4, 0.8, and 2.5 mg per kg poly-mer addition is given in Figs. 6-9 as a function of pH together with adsorp-tion at the three higher dosages. Even at only 0.1 mg per kg polymer addi-tion, the zeta potential is altered markedly at all pH values above 2, and at

It

~ ".1..z.....0Q.

C -10.....N

~ ~ ..,' '.

--.J ---"' ~ J I I J J.-

CJ

()

(J

I: 3"O-2""'OI/,..3NOCI

T . 2~ i '.CS/L . 005%

-20 CONC POLYMER. 0' "'9/"9, ,~ . . , , , , I

56789101112pH

Fig. 6. Zeta potential of quartz as a function of pH at 0.1 mg per kg PAMA dosage underconstant ionic-strength conditions.

79

0.4 mg per kg, it reaches a value of about +12 mV which shows very littlevariation with pH and further addition of polymer. On the other hand, poly-mer adsorption increases with both pH and polymer dosage. The increase ofadsorption with pH suggests that electrostatic forces playa significant butnot exclusive role in the adsorption of this polymer on the quartz surface.Electrostatic force is not considered to be the exclusive controlling param-eter because, even at the isoelectric point of quartz, there is a measurableeffect of polymer adsorption on zeta potential even though the adsorption

I - 3010-2 kmol/m3 NoCI

r-24J.l.CS/L - 005"1.

CONC POLYMER. 0.4 mg/kg

., .

~E

~tooZWtoo

fc .10toowN

~

~E>--t:VIZ&oJ0Z0

1 -:Go~0VI0d

- - - - -'-' '- ~~~~~~~~~~~ ~~~~~,~~

-.- --.M- - -,*", - - r:~'.., ..-30' . . , . I ,I I '-

7 3 4 5 6 7 8 9 10 11 12

pH

Fig. 7. Zeta potential of quartz and polymer adsorption on it as a function of pH at 0.4ml per kl P AMA do..,e under constant ionic-strenlth conditions.

+30

.,01

I.3'10-2k",OI/m3NoCIT.25.tI.C

S/L . O.b5%

CONC POLYMER. 0.8 "'9/kg._.:-::--~..,...().G-.=L-. ;:...~ .10

-'C

~ 0'"...aQ.

c -10...'"

c(" <t

~E,..-l-v;Z...0Z0~Q.Go0'"~

--~~~7~-"~fI ...t---

_]C)I . :--. . I I I I I q

2 3 4 5 6 7 8 9 10 11 12pH

Fig. 8. Zeta potential of quartz and polymer adsorption on it u a function of pH at 0.8mg per kg P AMA dosage under constant ionic-atrength conditions.

80

is minimal. This drastic effect on zeta potential could be due to both chargeneutralization and shift in the shear plane. It is suggested that, at 0.4 mg perkg and higher additions. polymer has coated the quartz surface sufficientlyfor the results to represent solely the zeta potential of the adsorbed polymerlayer (essentially independent of the charge of the quartz substrate).

+3"1 I

+201

I . 3 "0-2 kmol/m3 HoCI

T'2~+'.CSIL . O.O~%CONC. POLYMER . 2.~ ftlQ/kQ

~--o-~~--~-;J---~~_.~~_. -;->f +10

oJCto,Z 0...

~-1O r.....N

-20

~EI-~ZIIIQZ0

10=Q.8:0C/)C!

;;;~ ~~~~~..,- -~ ~~... ...""'~~ ~..,.~... ~~~..

-_G. A

.. ..-.,..--

~

.;;;...~~-30t..-~;.,.a""',:, I I . I . 4

2 3 4 5 6 1 8 9 10 11 12. pH

Fig. 9. Zeta potential of quartz and polymer adlOrption on it as a function of pH at 2.5ml per kg P AMA dosage under constant ionic-streDlth conditions.

Zeta potential and polymer adsorption in polymer-amine solutions

Figure 10 gives the zeta potential of quartz particles in solutions contain-ing both the polymer and the amine, together with polymer adsorption, as afunction of pH. In this series of experiments, a premixed solution of poly-mer and amine adjusted to the desired pH was added to a preconditionedsample of quartz suspension. Experiments were done to determine also theeffect of order of addition of polymer and amine; the results from these testsare given in Table 1.

It is noted from Fig. 10 that in the neutral and acidic pH regions, polymeradsorption is significant, but in the alkaline pH region the adsorption ofPAMA is prevented by the amine, which is most surface active in this pHrange. Most interestingly, the zeta-potential value obtained in the pH regionwhere polymer adsorbs is similar to the values obtained in solutions contain-ing polymer alone. It is to be noted that amine also adsorbs under the neu-tral pH condition (see the table in Fig. 3). Thus, even though amine also doesadsorb, the zeta potential measured is that of the polymer. Noting that flota-tion of quartz was totally depressed under these conditions, these resultsclearly suggest that the quartz particles with amine adsorbed on them arecoated by the polymer. The massive polymer species can be considered tomask the amine on the particles, generating a hydrophilic surface. The sug-gested model is shown schematically in Fig. 11a.

81

>e

oJ~...zw...

i

~WN

Fil. 10. Zeta potential of quartz and polymer adsorption u a function of pH in solutionscontaininl both the polymer (2.5 D1I per kg) and dodecylamine (5 x 10-4 kmol mol).

TABLEt

Compariaon of zeta potential and ad80rption in quartz/amine, quartz/PAMA, and quartz/amine/P AMA systems

pH Zeta rpAMA rAmiDe

69.6

10.210.4

69.6

10.210.4

69.6

10.210.4

69.6

10.210.4

Quartz/amine -6.5+16.5+26.8+26

+10+9.5

+10+10

+9+25+27+23

+17.5

+21.5

0.0521.051.051.05

1.2.21,

1.000

Quartz/PAMA -

Quartz/amine/p AMA(amine andP AMA addedlimultaneoully)

Quartz/amine/PAMA(polymer added rlrSt)

0.072

0.1061.171.171.17

0

0

-

.1

.4

.95

.4

82

Noting that the polymer P AMA did adsorb on quartz in alkaline solutionsbut did not when amine was present, tests were conducted to determinewhether the amine can possibly cause desorption of the polymer around pH10 where amine is most surface active. These experiments entailed condition-ing of the mineral first with the polymer and then with amine. If polymeradsorption is irreversible, when amine is added after the polymer hu alreadyadsorbed, the zeta potential should be about +10 mV, the value obtained inthe absence of amine. However, the zeta potential results at pH 9.6 and 10.4are +17.5 and +21.5 m V, respectively (Table 1). Also, the polymer adsorp-tion in both tests is zero. These zeta-potential values are similar to the valuesobtained with amine alone (some difference results from the extreme sensi-tivity of the zeta potential of quartz in amine solutions around pH 10). Since

-

Fie. 11. (a) Schematic reprelentation or the cationic polymer PAMA and dodecylamineco-adlOrption on quartz particles resultina in their notation depreuion. (b) Schematic re-prelentation or quartz/dodecylaulronate system. (c) Schematic representation or thecationic polymer PAMA and dodecylaulronate co-adsorption on quartz particles resultinein their notation activation.

84

Electrokinetic experiments conducted together with adsorption proved tobe a powerful method of studying the nature of polymer-surfactant inter-actions that are responsible for the observed effects on particle wettability ofthese reagents. While the presence of amine alone produced increasingchanges in the zeta potential with increasing pH, with maximum effectaround pH 10, polymer addition alone even at a dosage as low as 0.4 mg perkg yielded a constant value of about +10 mV (possibly characteristic of thequartz surface masked by polymer) in the complete pH range. Even whenthe polymer and the surfactant were present together in the system, a zetapotential near +10 m V was obtained in the acidic and neutral pH regionswhere polymer adsorption had occurred. Noting that the amine adsorptionunder these conditions did not make the quartz particles hydrophobic andthat it did not influence the zeta potential, a model is proposed where themassive polymer species adsorb on the amine-eoated particles masking theadsorbed amine. This model is supported by the activation by P AMA ob-served for sulfonate adsorption on quartz particles and their flotation.

ACKNOWLEDGEMENT

The authors acknowledge the Chemical and Process Engineering Divisionof the National Science Foundation for support of this work.

REFERENCES

1 J.W. Villar and G.A. Dawe, Min. Coner. J., 61 (1975) 40.2 P. Somasundaran, in P. Somasundaran (Ed.), Beneficiation of Mineral Fines, AIME,

New York, NY, 1979, pp. 183-196.3 P. Somasundaran and L.T. Lee, Sep. Sci. Technol., 16 (1981) 1475.4 P. Somasundaran and L.T. Lee, Polymer-Surfactant Interactions in the Flotation of

Quartz and Hematitie, International Mineral PrOcelSing Congress, Preprints, 1982,IV 9.1-IV 9.17.

5 BM. Moudgil and P. Somasundaran, Adsorption of Charged and Uncharged Poly-acrylamides on Hematite, Society of Mining Engineers, 1982, Preprint, pp. 82-160.

6 P. Somasundaran, in P. Somasundaran (Ed.) Fine Particles ProceasiDi, Vol. 2, AIME,New York, NY, 1980, pp. 946-976.

7 L. Usoni, G. Rinelli, A.M. Marabini and G. Gbiii, Selective Properties of Floccu-lants and Possibilities of Their Use in Flotation of Fine Minerals, VIIIth Interna-tional Mineral Processing Conrress, Leningrad, 1968, paper D-13.

8 G. Ghili and C. Botre, Trans. Inst. Min. Metall. Sect. C, 75 (1966) 240.9 G. Gbigi, Trans. Inst. Min. Metall. Sect. C, 78 (1968) 212.

10 J. Szczypa and S. Chibowaki, Colloids Surfaces, 3 (1981) 393.11 P. Somasundaran and B.M. Moudgil, in R.B. Seymour and G.A. Stahl (Eds.), Macro-

molecular Solutions, Pergamon, New York, 1982, pp. 151-165.12 J. Rubio and J.A. Kitchener, Trans. Inst. Min. Metall. Sect. C, 86 (1977) C97.13 S. Saito and Y. Mizuta, J. Colloid Interface Sci., 23 (1967) 604.14 M.J. Schwuger, J. Colloid Interface Sci., 43 (1973) 491.15 E.D. Goddard and R.B. Hannan, in K.L. Mittal (Ed.), Micellization, Solubilization

and Microemulsions, Plenum, New York, NY, 1977, pp. 835-845.

88

these "polymer first - amine second" tests yielded a value for zeta potentialclose to that obtained when both reagents were added simultaneously. it ispossible that in this case the polymer molecule was displaced by the compet-ing amine-aminium complex. This suggests that polymer desorption can beinduced by appropriate competing species. Similar desorption of hydrolyzedpolyacrylamide from clay has been achieved recently using phosphates [30].Whereas desorption was not induced by mere dilution (Fig. 1), in this casedesorption is possible since sites vacated by individual segments can now beoccupied by the competing species resulting eventually in the desorption ofthe entire polymer molecule.

On the basis of the model proposed here, it should be possible to floatquartz using an anionic surfactant even though nonnally quartz will not re-spond to an anionic surfactant (Fig. 11b,c). Flotation experiments con-ducted with dodecylsulfonate (together with PAMA) showed that quartz canindeed be floated completely with this reagent combination (Fig. 12) [4].Adsorption experiments showed quartz to extract the sulfonate from thesolution but only in the presence of P AMA (see table in Fig. 12). In additionto interactions of the polymer and the surfactant on the particle surface.interactions in the bulk liquid [11] also can contribute to the activation ofquartz by P AMA for flotation using the anionic surfactant. but they are notconsidered to be primarily responsible for the observed flotation.

0 , 10 100

POLYMER CONCENTRATION.mQ/kQ

Fig. 12. Activation of notation of quartz u8ing dodecylaulfonate by the cationic polym@rP AMA at natural pH. AdlOrption of 1U1fonate in the pre8@nce and abeence of the polymeria shown in the inlet.

Concluding remarks

Flotation of quartz by amine is depressed by the cationic polymer P AMA,while the amine adsorption itself is not affected.

84

Electrokinetic experiments conducted together with adsorption proved tobe a powerful method of studying the nature of polyme~urfactant inter-actions that are responsible for the observed effects on particle wettability ofthese reagents. While the presence of amine alone produced increasingchanges in the zeta potential with increasing pH, with maximum effectaround pH 10, polymer addition alone even at a dosage as low as 0.4 mg perkg yielded a constant value of about +10 mV (possibly characteristic of thequartz surface masked by polymer) in the complete pH range. Even whenthe polymer and the surfactant were present together in the system, a zetapotential near +10 m V was obtained in the acidic and neutral pH regionswhere polymer adsorption had occurred. Noting that the amine adsorptionunder these conditions did not make the quartz particles hydrophobic andthat it did not influence the zeta potential, a model is proposed where themassive polymer species adsorb on the amine-coated particles masking theadsorbed amine. This model is supported by the activation by P AMA ob-served for sulfonate adsorption on quartz particles and their flotation.

ACKNOWLEDGEMENT

The authors acknowledge the Chemical and Process Engineering Divisionof the National Science Foundation for support of this work.

REFERENC~

1 J.W. Villar and G.A. Dawe, Min. Contr. J.,61 (1975) 40.2 P. Somuundaran, in P. Somuundaran (Ed.), Beneficiation of Mineral Fines, AIME,

New York, NY,1979, pp.183-196.3 P. Somuundaran and L.T. Lee, Sep. Sci. Technol., 16 (1981) 1475.4 P. Somaaundaran and L. T. Lee, Polymer--Surfactant Interactionl in the Flotation of

Quartz and Hematitie, International Mineral Proceuine Conrreu, Preprintl, 1982,IV 9.1-IV 9.17.

5 B.M. Moudeil and P. Somuundaran, Adsorption of Charged and Unchareed Poly-acrylamidea on Hematite, Society of Minine En,meen, 1982, Preprint, pp. 82-160.

6 P. Somuundaran, in P. Somaaundaran (Ed.) Fine Particles Proceuine, Vol. 2, AIME,New York, NY, 1980, pp. 946-976.

7 L. Usoni, O. Rinelli, A.M. Marabini and G. Ghiei, Selective Propertiea of FJoccu-lantl and Pouibiliti.. of Their Use in Flotation of Fine Minerall, VllIth Interna-tional Mineral Proceuine Contreu, Leninerad, 1968, .-per D-13.

8 G. Ghili and C. Botre, Trans.lnlt. Min. Metall. Sect. C, 75 (1966) 240.9 G. Ghili, Trans. Inat. Min. MetalJ. Sect. C, 78 (1968) 212.

10 J. Szczypa and S. Chibowlki, Conoids Surface., 3 (1981) 393.11 P. Somuundaran and B.M. Moud(i), in R.B. Seymour and G.A. Stabl (Eds.), Macro-

molecular Solutionl, Pereamon, New York, 1982, pp. 151-165.12 J. Rubio and J.A. Kitchener, Trani. Inlt. Min. Metall. Sect. C, 86 (1977) C97.13 S. Saito and Y. Mizuta,J. Colloid Interface Sci., 23 (1967) 604.14 M.J. Schwueer, J. Colloid Interface Sci., 43 (1973) 491.15 E.D. Goddard and R.B. Hannan, in K.L. Mittal (Ed.), Micellization, Solubilization

and MicroemuJaiona, Plenum, New York, NY, 1977, pp. 835-845.

85

16 M.N. Jones, J. Colloid Interface Sci., 23 (1967) 36.17 H. Arai, M. Mukata and K. Shinoda, J. Colloid Interface Sci., 37 (1971) 223.18 E.D. Goddard and R.B. Hannan, J. Am. Oil Chem. Soc., 54 (1977) 561.19 E.D. Goddard and R.B. Hannan, J. Colloid Interface Sci., 55 (1976) 73.20 K.E. Lewis and C.P. Robinson, J. Colloid Interface Sci., 32 (1970) 539.21 S. Saito, J. Colloid Interface Sci., 23 (1967) 227.22 B. Cabane, J. Phys. Chem., 81 (1977) 1639.23 B. Kalpakci and R. Nagarajan, Surfactant Binding to Polymer and Phase Separa-

tion in Aqueous Surfactant-Polymer Solutions, AIChE Meeting, Houston, April,1981.

24 N.J. Turro, B.H. Baretz and Ping.Liu Kuo, Macromolecules, 17 (1984) 1321.25 G.W. Powers, The Volumetric Determination of Organic Sulfonatea by Double Indi-

cator Method, Communication C.225, Amoco Production Co., Tulsa, 1970.26 P. Somaaundaran, J. Colloid Interface Sci., 31 (1969) 557.27 G.A. Parks, Chem. Rev., 65 (1965) 177.28 K.P. Ananthapadmanabhan, P. Somuundaran and T.W. Healy, Trans. AIME, 266

(1980) 2003.29 P. Somuundaran and K.P. Ananthapadmanabhan, in K.L. Mittal (Ed.), Solution

Chemistry of Surfactanta, Plenum, New York, NY, vol. 2, 1979, pp. 777-800.30 P. Dodson and P. Somuundaran, J. Colloid Interface Sci., 97 (1984) 481.