Flocculation of Sulfide Mineral Fines by Insoluble Cross-Linked Sitarch

OVE FRCM LIBRARY PLEASE 00 NOT REM r !::'" iRli 8819 . ~ Bureau of Mines Report of Investigations/1983 . ~ I [

Floccu lation of Sulfide Mineral Fines by Insoluble Cross-Linked Sitarch Xanthate

By S. C. Termes, R. l. Wilfong, and P. E. Richardson

UN ITED STATES DEPARTMENT OF THE INTERIOR Report of Investigations 8819

Flocculation of Sulfide Mineral Fines by I nsoluble Cross-linked Starch Xanthate

By S. C. Termes, R. l. Wilfong, and P. E. Richardson

R ECE IVED

NOV2 g 1983

UNITED STATES DEPARTMENT OF THE INTERIOR James G. Watt, Secretary

BUREAU OF MINES Robert C. Horton, Director library oJ Corlgr1ess Cataloging Itl Publicalion Dala

Termes, S. C. (Si Ivia C.) Flocculatlon of sulfide miller'! fines by insoillb (' cros:>-linked sta,,;h " .. nthate.

(J)lJreau of ~1ine" repon of inl'<:stigi.ltlons : 8819) Bibliography: p.22-23. Supt, of Docs. no.: I 28.2'1:88J9, 1. Ore-dressi ng. 2. F I Ol'Cll\atlOn. 3. Su I ph ides. ,i. Starch x an­ dUlfe. I. Wilfollg, IL L. (Hor L.l. 11. l{i,'hards"!1. Paul I:. [11. Title, IV. SHles: Report inV<;$tiflatlOns (Unl(~d Slules. Bureau (Jf ~1lneS'1 j 8819.

TN23. U43 52111 622:::; .751 R3-600H9 CONTENTS

Abstract...... 1 Introduction...... •.•.•...... ••••••.•••..•.••.••••....•.•••••...... •.•. . ... • 2

Acknowledgmen ts ...... It ...... Ii • ...... • • .. .. • 2 Background. • . • . . • • . . •. . . • • • . • . . . • • • . • • • . • • ...... • . • . . . . • • . . . • . 2 Experimental...... ••..••....••••.••. 3 Re ag e n t s .. ~ ...... , ...... ") • • • • • • • • • • .. • • .. • • • • • • • • • • • 3 Synthesis and characterization of ISX...... 3 Mineral preparation...... 4 Flocculation experiments...... 5 Other measurements...... 5

Re suI t s •••••••••••• II • II •••••••••• II • • • • • • .. • • • .. • • • • • • • .. • • • • • • • • • • .. • • • • • • • • • • • • • • • • 6 Single-mineral pulps...... 6 Zeta-potential measurements...... 10 ISX dosage and pulp density...... 12 Effect of mineral weathering on flocculation...... 13 Flocculation of sulfide mineral-quartz mixtures...... 17 Discussion. .•. .. •.••...... ••....•.....•••..•. .•...... • ...... ••.•••.....•• 21 Summary... •...••••. .•••..••.. .••••....••.•...... ••. .••. ••• ..•••• .•• ..••..•.. 22 Re fer e n c e s ...... • • • . • . . . . • . • . • ...... • . . • . • • . . . • • • . • • . • . • . . . • . • • . • . . • . . . . • • 22

ILLUSTRATIONS

1. Components of starch...... 3 2. Infrared spectra of CLS and ISX...... 5 3. Tilted plate elutriator...... 6 4. Settling of covellite...... 7 5. Settling of chalcocite. ..•.•••.•••...•.•••••••.....•••••••....•••••••••... 7 6. Settling of pyrite...... 9 7. Settling of pyrrhotite...... 9 ·8. Settling of chalcopyrite...... 9 9. Set tling of bornite...... 9 10. Settling of sphalerite...... 10 11. Settling of galena...... •••...... •. ••••. .•. .... ••••• ••• 10 12. Settling of molybdenite...... 10 13. Settling of quartz...... 10 14. Zeta potential of CLS and ISX...... 11 15. Zeta potential of freshly ground covellite and chalcocite...... 11 16. Zeta potential of freshly ground pyrite and pyrrhotite...... 12 17. Zeta potential of freshly ground chalcopyrite and bornite...... 12 18. Zeta potential of freshly ground sphalerite, galena, and molybdenite...... 13 19. Turbidity as a function of the weight ratio of ISX to covellite...... •. 14 20. Total copper content as a function of the weight ratio of ISX to covellite 14 21. Zeta potential of weathered pyrite... ••...... ••.•...... •••••••••.•••••.• 15 22. Infrared spectra of pyrite...... 16 23. SEM photomicrographs of pyrite fines...... 18 24. Zeta potential of weathered chalcopyrite...... 19 25. Zeta potential of weathered bornite.. .•••.•...•••.•••.•...... •.•...... •... 19 26. Selective flocculation of bornite from a mixture with quartz...... 20 ii

TABLES

1. tical data on mineral specimens...... 4 2. Effect of pH of ISX addition on flocculation...... 8 3. Zeta potentials at the pH of maximum flocculation by ISX when added at pHn' II. 4. Points of zero and pHn of suspensions of sulfide fines...... 17 5· Selective flocculation of bornite from quartz...... 20

angstrom ter

cm- J re centimeter mm millimeter

g gram rna month

gil gram per liter mv millivolt

hr hour NTU tric turbidity unit Ilg microgram

min minute yr year FLOCCULATiON OF SULFiDE MiNERAL FiNES BY !NSOLUBLE CROSS·i_INKED STARCH XANTHATE

By S. C. Termes, 1 R. L, Wi Ifong, I and P, E. Richardson 2

ABSTRACT

The Bureau of Mines conducted research on the flocculation of various minerals with insoluble cross-linked starch xanthate (ISX) to determine its potential as a beneficiation technique for low-grade, highly dissem­ inated ores and for selective desliming. Covellite, chalcocite, pyrite, pyrrhotite, chalcopyrite, bornite, sphalerite, galena, and molybdenite fines flocculate with ISX. Floc formation, floc size, and settling rate are dependent on pH, with the pH dependence differing for each mineral. Quartz is not flocculated by ISX. Experiments to obtain selective floc­ culation of sulfides from quartz were attempted. Good selectivity was only obtained for the bornite-quartz system. postflocculation separa­ tions resulted in flocculated bornite in grades as high as 92 pet. Evi­ dence is presented that the flocculation of many of the ~ulfide minerals with ISX may involve covalent bonding of the xanthate group to lattice metal site(s).

1Research chemist. 2supervisory physicist. Avondale Research Center, Bureau of Mines, Avondale, MD. 2

INTRODUCTION

Because of the increasing interest in in flotation circuits by the formation selective flocculation as a beneficiation of covalent bonds between the xanthate technique for low-grade, highly dissemi­ group and surface metal component(s) of nated ores and for selective desliming, the mineral (4); (2) cross-linking of the Bureau of Mines has been investigat­ starch prior to xanthation results in a ing the flocculation beiavior of several high-molecular-weight polymeric backbone cross-linked starch derivatives contain­ that generally favors floc strength; (3) ing chelating groups. This report dis­ ISX is prepared from easily renewable cusses the flocculation of sulfide miner­ sources, and it is more stable and easier al fines by insoluble cross-linked starch to handle than the soluble, alkali metal xanthate (ISX). starch xanthates previously studied by Chang (5) and Brown (6) for the benefici­ Polymeric materials such as ISX, which ation of iron ores, and Brown and C~cil contain a chelating group of known re­ (7) for the concentration of sylvite from activity towards specific mineral sur­ sylvinite ore. faces, were first proposed by Slater, Clark, and Kitchener (1) ,3 Kitchener CD, The ISX reported in this paper as a and Attia and Kitchener (3) as selectIve flocculant for sulfide mineral fines was flocculants for mineral fInes with parti­ developed by Wing and Doane (8-9) at the cle aggregation possible through a bridg­ U.S. Department of Agriculture~ Northern ing mechanism. ISX appeared to be at­ Regional Research Center, Peoria, IL, for tractive as a sulfide mineral flocculant the removal of heavy metal ions from because (1) alkyl xanthates are known to waste waters. react selectively with sulfide minerals

ACKNOWL.E.D.GMENTS

The authors express their appreciation Regional Research Center, Peoria, IL, for to Dr. Robert E. Wing, research chemist, helpful discussions on ISX. U.S. Department of Agriculture, Northern

BACKGROUND

Starches are composed of two polysac-­ of D-(+)-glucose units (fig. lA) joined charide fractions, amylose and amylopec­ in a-l,4-glycoside linkages. Amylose tin. The ratio of these fractions is chains are linear (fig. 18) while amylo­ somewhat variable for each type of starch pectine is a branched polymer with side (that is, corn, potato, rice, etc.). chains attached through a-l,6-glycoside Both amylose and amylopectin are made up linkages (fig. lC). Neither of these fractions are soluble in water. Amylo­ 3 Un derlined numbers in parentheses re­ pectin dispersions in water are relative­ fer to items in the list of references at ly stable, but amylose dispersions can be the end of this report. regarded as metastable. 3

A Cross-linking in starch involves par H ticipation of the hydroxyl groups. It is a nondegradative reaction where intermo­ lecular bridges (cross-links) are formed by reagents having multiple reactive sites such as epichlorohydrin, formalde­ hyde, and phosphorus oxychloride. Inte~­ molecular bridging results ,in an increase in the molecular weight of the polymer.

8 The cross-linked starch used in the preparation of ISX is an epichlorohydrin cross -linked product that can be repre­ sented as

where DCL represents the degree of cross­ linking.

Xanthation of starch proceeds ceadily in strong alkaline solutions. The pri­ mary hydroxyl group, C-6, is the princi­ pal group involved in the xanthation re- 3ction (see figure 1). Alkali metal starch xanthates degrade rapidly in aque­ ous solutions, while the alkaline-earth and heavy metal salts are more stable. The magnesium derivative of cross-linked starch xanthate, which is known as ISX, a= OH was found by Wing and Doane (8-9) to pro­ R= CHpH duce the mos t desirable product'- in terms of room temperature stablity, effective­ FIGURE 1. 0 Components of starch. ii, D.(+)· ness in heavy metal removal, and lower glucose; H, amylose; (', amylopectin. production cost. EXPERIMENTAL KEAGENTS Chemical Co. was used in preparing the xanthate derivative. Unless otherwise specified, chemi­ cals were reagent grade and water was SYNTHESIS AND CHARACTERIZATION OF ISX distilled and deionized. A commercial highly cross-linked starch (CLS) marketed ISX was prepared according to the fol­ as Vulca 9()4 from the Na tional Starch and lowing method described by Wing (9):

Mg2+ CLS + NaOH~ Causticized ------+1 Xanthate ------+) ISX. starch derivative (Na+ salt)

4Reference to specific trade names or manufacturers is made for identification pur­ poses only and does not imply endorsement by the Bureau of Mines. 4

Crude ISX is a pale orange, rather wet Chemical analysis of ISX with a D.S. of solid. Washing with water is necess9ry 0.4 yielded the following, in percent: to remove unreacted material and impuri­ sulfur, 8.27; ash, 19.6; water, 12.7; ties. Successive washings with acetone magnesium, 1.38. The infrared spectra of and ether leaves a pale yellow, finely CLS and ISX are shown in figure 2. powdered material stable for at least Xanthate-related bands are indicated in yr when kept in tightly closed glass the ISX spectrum. containers under refrigeration. At room tempera ture, the life of ISX is a few MINERAL PREPARATION months. With aging, ISX turns dark yel­ low and has a foul smell. Addition of Mineral specimens were obtained from ISX to aqueous solutions produces an Ward's Natural Science Establishment, New increase in pH. Both ISX and CLS dis­ York. Handpicked crys tals were dry perse well in water at concentrations be­ ground to minus 400 mesh with an agate low 25 gil. mortar and pestle. Freshly ground miner­ als were used unless otherwise specified. The degree of substitution (D.S.) was X-ray diffraction data showed that the determined by the acidimetric method de­ samples were essentially monomineralic, scribed by Swanson and Buchanan (10). except for the pyrrhotite sample which IXS with D.S. values between 0.2 and 0.4 also contained pentlandite. Table 1 pre-­ were obtained, which is within the range sents analytical data and origin of the recommended by Wing and Doane (8-9) for minerals. effective removal of heavy metal-ions.

TABLE 1. - Analytical data on mineral specimens

Mineral Origin Constituents Main elements, 1 pct Covellite, CuS •••• Butte, MT ••••••••••• C<=w€l-li-t€, py-rite­ Cu 63.1 (66.5), (minor to trace). Fe 1. 73.

Chalcocite, Cu 2S .. Messina, Transvaal •• Chalcocite •••.•....••. Cu 79. 1 (79. 8) •

Pyri te, FeS 2 •••••• Ambasaguas, Spain ••• Pyrite ••••..•...... •.• Fe 44.2 (46.5).

_ Pyrrhotite, Fe 1 x S Ontario, Canada ••••• Pyrrhoti te, Fe 55.9,2 Ni 6.10,2 pent landite. Co 0.3. 2

Chalcopyrit e, Messina, Transvaal •• Chalcopyri te •••••••••• Cu 34.3 (34.6), (Cu,Fe)S2' Fe 31.9 (30.4).

Aj 0 I AZ ••••.•••.•••• Bornite, pyrite (minor Cu 6 1. 7 (63 • 3) , to trace). Fe 10. 3 (11. 1 ) •

Sphalerite, 2nS ••• Santander, Spain . ••. Sphalerite, wurtzite 2n 66.1 (67.1). (minor to trace).

Galena, PbS ••••••• Galena, KS •••••••••• Galena ...... Pb 86.2 (86.4).

Molybdenite, MoS 2 • Ko rea., •••••••••••••• Molybdenite, quartz Mo 58. 1 (5 9 • 9) • (minor to trace).

Quartz, Si02 •••••• Brazil ••...... •.... Qtlartz •. ., •.•••.••.•..• Si 45.4 (47.1). lNumbers ln parentheses refer to the percent of the maln element, assUDllng a pure sample. 2Variable stoichiometry of Fe in pyrrhotite and of Fe, Ni, and Co in pentlandite. 5

100 KEY : " c:; CLS I,'·' a. : '.' 80 ISX " .- w ' .~ .',/ () .,,/ . Z .' ' ... ~. < ' . .-, - I- 60 t:: 100 \!; ~ , V en CoS Z 60 < .... ;' '" a:: 40 ~ I- 20 4,000 3,000 2,000

20 1 I I 1 ,800 1 ,600 1 ,400 1 ,200 1 ,000 800 600 400 200

FIGURE 2. a Illfrared spectra of CLS and ISX, Xanthate-related bands are illdicated in the ISX spectrum.

FLOCCULATION EXPERIMENTSS Postflocculation separations were per­ f ormed in two ways: (1) decantation of Flocculation tests were performed in the suspended minerals, followed by wash­ 100-ml graduated cylinders fitted with ing of the flocs to remove nonflocculated ground glass stoppers. Unless otherwise mineral(s), and repeating the operation specified, 3-g samples of each mineral as necessary to clean the flocs from the were suspended in 80 ml of water. Dilute nonflocculated, trapped material; and (2) RCl and NaOH solutions (O.OlM, O.lM, and by using the titled plate elutriator il­ 1.0M) were used to adjust- the pH to lustrated in figure 3. This apparatus is the- desired values prior to flocculant an adaptation of the one described by addition and for any subsequent pH Friend, Iskra, and Kitchener (11), where adjustments. washing of the flocs is performed by a counterflow of water. The unflocculated To determine the effectiveness of ISX minerals are collected at the top, while as a flocculant, separate runs were made the flocs are collected at the bottom. in the absence of any starch (acid-base additions only) and in the presence of OTHER MEASUREMENTS CLS. The desired weight of CLS or ISX (0.1 or 0.2 g) was dispersed in 20 ml of Zeta potentials were measured with a water immediately before addition to the commercially available zeta-meter follow­ mineral pulp. Mixing was done manually ing established procedures (12-13). Tur­ by shaking and inverting the closed cyl­ bidities were measured with -a~rbidime­ inder for 1 min, after which the cylinder ter. Turbidities above 200 NTU were was set on a bench and visible changes in obtained by diluting aliquots of the the height of settled solids, clarifica­ original sample to give turbidity values tion, and floc size were recorded at var­ below 200 NTU and then extrapolating the ious time intervals. results to obtain the turbidity of the original sample. Infrared spectra were To determine the selectivity of ISX, recorded with a commercially availa­ synthetic mixtures of selected sulfide ble grating infrared spectrophotometer. minerals and quartz were prepared and the Samples for infrared studies were pre­ flocculation tests repeated as above. pared as KBr pellets. Photomicrographs were taken with a scanning electron 5perform;~ by Heidi C. Triantafillou, microscope. chemist, Avondale (MDi Research Center. 6

FIGURE 3 .• Tilted plate elutriator. II, Water inlet; B, screen or frilled glass plate, 25 to 50 11m porosity; C, elutriant outlets, 0, floc outlet; F.; slurry inlet; F, flow regulators,

RESULTS

SINGLE-MINERAL PULPS The results are shown in figures 4 through 13 for freshly ground fines of Initial tests to assess the ability covelli te, chalcocite, pyri te, pyrrho­ of ISX to flocculate suspensions of sul­ tite, chalcopyrite, bornite, sphalerite, fide mineral fines and quartz, and galena, molybdenite, and quartz as a the influence of pH on flocculation be­ function of pH in the presence of ISX, havior, involved measuring the height CLS, and for acid-base additions only. of settled solids. Although the height Additions of ISX and CLS were done at the ) is not a quantitative measure of min­ natural pH (pH n of the mineral pulp. eral removed from the pulp, it is a The pH range where good flocculation and measure of floc formation and floc maximum visual clarification occurred is size. indicated by the dashed region of the curves. j

361~ When compared with acid-base additions t;f only or with CLS treatment, the most pro­ KEY 1\ nounced effect in the height of settled I \ solids due to ISX was observed for covel­ 32 6. ISX I \ o CLS I \ lite (fig, 4), bornite (fig. 9), pyrite I \ o Acid base I \ (fig. 6), and sphalerite (fig. 10). A I \ moderate increase in height with ISX was 28 I obtained with chalcopyrite (fig. 8) and I I pyrrhotite (fig. 7). Although ISX ap­ ,I peared to produce a negligible effect on 24 ,I the height of settled solid for galena (fig. 11), rapid settling was observed at E ~{'I, E pH 6 and 11 (table 2). Chalcocite (fig. ,I :g 20 , 5) and molybdenite (fig. 12) formed small :::::i I flocs with ISX but settling was relative­ o I (/) ly slow. No floc formation or improved I c settling was obtained with quartz (fig. ~ 16 l- 13). Cross-linked starch induced some I- W floc formation on pulps of bornite and (/) pyrite and relatively large flocs with 12 pyrrhoti te. In general, the pH range of best pulp clarification and maximum flocculation by ISX varies for each 8 mineral. Table 2 summarizes the results of adding ISX at pH values other than 4 • pH n For bornite, the pH of addition has essentially no effect upon the range where good flocculation and o L ----~----~----~ clarification occur, but for the other 2 4 8 10 12 minerals the pH of addition has a pH slight effect on the flocculation be­ havior. In some instances, no ISX­ FIGURE 4. -- Setlling of covellite. induced clarification was observed, as in the case of adding ISX to chalcopyrite at 8 ---'----T----,-- - - ,---- pH 9.4.

KEY i\ I [':, ISX The average floc size range was between / 0.5 to 3 mm except for bornite. Addition "- CLS ,0- --.r< E 6 o Acid base I of ISX at pH for bornite produced rapid I n E I (/l formation of flocs in the size range of Cl ::::; 0.5 to 1.0 mm. These small flocs further o CI) 4 aggregated in the pulp during a presedi­ Cl W mentation period of about 3 to 5 min, -' I-­ '/:1 and formed floc aggregates as large as 7 I­ W CI) to 8 mm, which then fell rapidly through 2 the suspension. If the cylinder was slightly tilted and subjected to a gen­ pHn tle rotating motion, floc growth was o------~----~~I------~---- greatly enhanced. This observation has 2 4 6 8 10 12 been reported previously by Yarar (14-15) pH in the flocculation of mineral fineS-with FIGURE 5. - Settling of chalcocite. polymers. 8

TABLE 2. - Effect of pH of ISX addition on flocculation

Mineral pH at ISX pH after 1st pH of fastest settling addition addition and clarification Covellite • •.•••••••. 2.7 5.6 7- 8 5.1 6.0 6- 7 6.1(pH n ) 9.5 6- 9 10.9 11.0 5- 7

Chalcocite •••••••••• 2.8 6.1 8-11 7.2(pH n ) 10.8 9-10 10.7 11.1 9-10

Pyrite ••••••••••.••• 3.3 9.0 7-11 6.5(pH n ) 10.0 6-10 11.6 11. 6 6-10

pyrrhotite •••••••••• 2.3 3.2 7-12 5.4(pHn ) ~1O 6- 8.5 11.9 12.0 8-11

Chalcopyrite •••••••• 3.2 10.3 5- 6 5.6(pHn ) 11.3 00:6 9.4 10.9 NO

Bornite •.•••.••••••• 5.0 8.0 8-10 6.9(pH n ) 10.0 8- 9 10.0 -11. 0 &- 9

Sphaleri te 1 ••••••••• 3.1 10.0 NO 6.5(pH n ) >10 7-10 11.3 11.3 NO

Galena •••. ..•.•.•... 3.2 ~7 6- 7 5.8(pHn ) >10.5 6, 11 10.9 11.2 6, 11 2 Molybdeni te •••••••• 2.8(pH n ) >10 NO 11.8 12 NO NO Not observed. I lDecomposition of ZnS and/or ISX noted at pH <4. 2Considerable flotation of molybdenite observed at pH >12.

An interesting feature of bornite floes components can be readily removed by is that although they appear to break in­ postflocculation mechanical treatments. to smaller fragments upon shaking, re­ Floes of the other minerals readily break agglomeration into large floes occurs apart upon shaking or washing and show continuously. More importantly, even if little tendency to re-form. the floes are separated from their super­ natants (for example, by filtration) and It was observed that ISX-flocculated then redispersed in water, reagglomera­ minerals filtered readily in ordinary tion into larger floes is observed, sug­ vacuum and gravity filtrations, leaving gesting that entrapped, nonflocculated clustered particles on the filter paper. 36

16 32 II II 1\ ~ ,.c;. II KEY I KEY I' \ 1\ {:;:,. ISX 14 I 6. ISX 28 \ I I 0 CLS \ o CLS I \ o Acid base \ o Acid base I I \ I I I I \ \ E 24 I 12 \ E I I en" ~6-~ E \ 0 E I ::; ~! vi 0 20 ~ Cl 10 ~ en ::::i 0 0 w en -' Cl f- lLI f- ..J 8 w 16 f- en entu

6 12

4 8 l

2 ~L _ _ .~ p r I I I I 4 6 8 10 12 8 10 12 14 pH pH

FIGURE 6. Settli ng of pyrite. FIGURE 7 " Settl i ng of pyrrhotile

14 ~ I \ I \ KEY \ 6. ISX 12 \ \ o CLS \ \ o Acid base \ \ 10 \ \ KEY \ E \ "~[', ISX E I 8 0 CLS \ en- \ Cl 8 o Acid base \ :::; 0 en E ~~ en E lLI vi -' 6 0 .... :; ~~ .... 0 enlLI III . ~ 0 UJ -' 4 ~ UJ III T 2 J pH n pH n I, _ 1 __ 0 I I 0 - - I- I I 2 4 6 8 10 12 2 4 6 8 10 12 pH pH

FIGURE 8.• Settling o f chalcopyr i te. FIGURE 9.• Settling of bo rnite. 10._------,------.------, ------.-

KEY 61sx ~, o CLS ,----- ·~I------.------.------,------' , , o Acid base , , KEY , 61S;( E , E , o CLS , , 6 II) 6 o Acid base I E Q ...J E o vi II) 0 o ::J UJ 0 ...J (f) 4 l­ 4 I­ 0 UJ UJ II) ...J l- I- UJ (f)

I I pr ol- I I J 2 4 6 8 10 12 2 4 8 10 pH pH FIGURE 10. - Settling of sphalerlfe. FIGURE 11. - Settling of galena.

~o ,------r------,r-

KEY 61sx o CLS 16 o Acid base E E vi Q ...J 0 12 E (f) E KEY 0 6 UJ en- ISX ...J l- ~ ~ ; CLS I- ...J UJ 0 Acid base (f) 0 1- en a 0 60L~ 6 000 6LI060 U60 :]0 O,P 8/ w ...J pH n r- P~n I r- w en 0 I 2 4 6 8 10 12 J2 - 4 6 8 10 12 pH pH FIGURE 12 ... Settling of molybdenite. FIGURE 13 .. Seilling of quartz.

This is in contrast with the nontreated mechanisms involved in the flocculation samples (acid-base additions only), which of the sulfide minerals by ISX. Suspen­ produce slimy residues, and with most sions of CLS and ISX and each of the un­ CLS-treated samples, where the settled treated, freshly ground sulfide minerals solids take longer to filter. were studied. Figure 14 shows the zeta potentials of CLS and ISX in the pH range ZETA POTENTIAL MEASUREMENTS6 of 3 to 11. For CLS, the zeta potentials are positive, with values increasing from Zeta potential measurements were made about +9 mv at pH 2.4 to about +25 mv at to gain insight into the reaction pH 9. On the other hand, ISX is nega­ tively charged with zeta potential of ~-8 6performed by Jeffrey A. Riehl, chem­ mv, essentially independent of pH. ist, Avondale (MD) Research Center. 11

30.----,----,---,----,----, 75.---~-- ---r---,_--- r_--_, KEY KEY /'::,. ISX 6. Covellile D CLS o Chalcocite 20 50

> E -' 10 > 25

I -10 -25

6 B 10J 12 -50 pH

FIGURE 14. " Zeta pot~ntial of CLS and ISX.

-75 '------'-----' 10 The zeta potentials as function of pH 2 4 6 8 12 for covellite and chalcocite are shown in pH figure 15. The point of zero charge FIGURE 15., Zeta potential of freshly ground (p.z.c.) for freshly ground chalcocite is covellite and chalcocite. pH 5.5 and the zeta potential is posi­ tive above this pH. Covellite (freshly ground) did not show a p.z.c.; the zeta­ p.z.c. at pH 4.9. Chalcopyrite and born­ potential values were negative and ranged ite (fig. 17) exhibit a similar pattern from about -35 to -65 mv. of positive zeta potentials at pH values below their p.z.c. (4.8 to 5.0 for chal­ Pyrite and pyrrhotite zeta potentials copyrite and 6.8 to 7 for bornite) and are illustrated in figure 16. Below pH negative above their p.z.c. 4.6 (p.z.c.) the zeta potentials of freshly ground pyrite are negative with a Figure 18 presents the zeta potentials value of approximately -10 mv; above pH of the sphalerite, galena, and molyb­ 4.6 the zeta potential becomes positive denite samples. The p.z.c. of sphalerite and nearly independent of pH. These occurred between pH 7.2 and 7.5, with results are in contrast with the zeta po­ maximum, positive zeta-potential values tential values obtained for the same occurring between pH 4 and 5. Above pH ground sample which was allowed to weath­ 10 the zeta potentials were increasingly er for several months (see figure 21 and negative. Galena did not show a p.z.c.; the "Effect of Weathering on Floccula­ above pH 4.8 the zeta potential was in­ t ion" section). Pyrrhotite containing creasingly negative. The zeta poten­ some cobalt-bearing pentlandite showed a tials of freshly ground molybdenite were 12

50

KEY KEY • Pyrite Fresh '\}• 18 mo • Pyrrhotite ~ 'l 25

> > E E ...J- 0 ...J 0

-50 -50

'-----~~____'___~~~..L ~~~----'---~~----' _75L-~~-L~~~~~~~~~~-L~~~ -75 2 4 6 8 10 12 2 4 6 8 10

pH pH FIGURE 16. - Zeta potential of freshly ground FIGURE 17. - Zeta potential of freshly ground pyrite and pyrrhotite. chalcopyrite and bornite. negative throughout the pH range of 3 to TABLE 3. - Zeta potentials at the pH 11. The zeta potential for quartz was of maximum flocculation by ISX when not measured in this study, but it is added at pHn known that the p.z.c. falls in the vicin~ ity of pH 2 (16-17) and that it has a Point of pH of bes t Zeta negative zeta potential above this pH. Mineral zero floccula- po ten- charge tion tial, Table 3 lists the pH range where best mv flocculation by ISX was found together Covellite •.• NO 7- 8.5 -40 with the experimental zeta-potential val­ Chalcocite •• 5.3-5.5 9-10 +20 ues and p.z.c. The "Discussion" section Pyrite •••.•• 4.6 5- 8 +10 presents an attempt to correlate the Pyrrhotite •• 4.9 6- 8.5 -25 flocculation mechanism by ISX with zeta Chalcopyrite 4.8-5.5 6- 7 -30 potentials, based on these results. Borni te ••••• 6.9 8-10 -25 Sphalerite •• 7.2-7.5 7-10 1+2 ISX DOSAGE AND PULP DENSITY 2-35 Galena •••••• NO ~6 -40 Since covellite formed large, rapidly ~11 -60 settling flocs upon addition of ISX, this mineral was chosen for a study of the Molybdenite. NO NO NAp effect of mineral pulp concentration and Quartz •••••• 31.8 NAp 4-25 ISX dosage on flocculation response. NAp Not appllcable. L pH 10. Turbidity measurements and total copper NO Not observed. 3Reference 16. content were used to assess the extent of 1pH 7. 4pH 8-10. mineral removal. 13

50 increase in turbidity may be due to dis­ KEY persed ISX and/or covellite. The in­ Sphalerite crease in copper content suggests that • Galena ISX may be acting as a dispersant for A Molybdenite 25 covellite. At ratios above 0.7, over­ dosage of flocculant may account for some of the decrease in turbidity and copper ,. content. It is noteworthy that for dos­ E ages above 0.1 g of ISX floes were not -' o formed or were too small to be observed ~ t­ in the highly turbid solutions. At the Z lJJ t­ higher dosages some foaming and foul odor O Q. were noted, presumably due to formation ~ -25 t- of CS 2 from decomposition of ISX. lJJ N EFFECT OF MINERAL WEATHERING ON FLOCCULATION -50 Pyrite fines were found to oxidize (weather) readily, even when kept dry in tight containers. Aged fines released F(III) and sulfate ions into solution -75L1 ______~ ______L- __~~ ______L ______~ 2 4 6 8 10 12 and, therefore, pulps of aged pyrite ex­ pH hibited lower pHn than pulps prepared from the freshly ground mineral owing to F IGUR E 18. - Zeta potent ia I of fresh Iy ground the hydrolysis of Fe(III). Pulps of sphalerite, galena, and molybdenite. weathered pyrite treated with ISX or NaOH produced a gelatinous, rust-colored pre­ The desired weight of mineral was dis­ cipitate resembling hydrous iron(III) ox­ persed in 80 ml of water. A known amount ides, which caused rapid floc formation of ISX (dispersed in 20 ml of water) was and nearly instantaneous settling of the added, mixed for 1 min, then allowed to mineral. Because hydrous iron(III) ox­ settle for 3 hr. Samples without ISX ides are known to be strong flocculants addition did not show evidence of aggre­ and coagulants (~-~), weathering of gation or fast settling at pulp concen­ pyrite, a common mineral in sulfide ores, trations above 0.1 g of covellite in 100 and its effect on selective flocculation ml of water, and the turbidity readings were studied in more detail. remained above the turbidimeter limit of 200 NTU. After 3 hr, the top 30 m1 of In mixtures of quartz and weathered supernatant was carefully withdrawn with pyrite where the pH was raised to 7 and a pipette, and the turbidity and total II with NaOH, a rusty color was detected copper content were determined. The tur­ in the collected settled fraction; this bidity and total copper concentration of coloration was absent when fresh ground the withdrawn supernatant as a function pyrite was used. X-ray diffraction anal­ of the weight ratio of ISX to covellite ysis of the rust-colored fractions showed are shown in figures 19 and 20, respec­ the presence of a poorly defined phase tively. The clearest supernatants and having broad, but not intense peaks, best mineral removal were produced at centered at 6.55 A (y-FeOOH has a major ISX-to-covellite ratios of less than 0.1. d-spacing of 6.26 A). The only other At low ISX dosages, floes formed nearly peaks were those of pyrite and quartz, instantaneously upon addition of the which suggests that the colored material flocculant. At ratios between ~0.1 and may be an amorphous hydrous iron(III) 0.6, both the turbidity and copper con­ oxide. tent in the supernatant increased. The 14

o 0.2 0.4 0.6 0.3 1.0 WEIGHT RATIO OF ISX TO COVEL LITE

FIGURE 19. ' Turbidity as a function of the weight ratio of ISX to covellite.

4,000 ----r------T- ··

----

3,000 C'l:::s. KEY ci w Grams of covellite in 0.. 0.. 100 ml of water 0 (,) 2,000 • 0.01 -l .1 « •0 .5 l- 12 • 1 ,0 1,000

- - -- - ~------

0.2 0.4 0.6 0.8 1.0 WEIGHT RATIO OF ISX TO cOVELLITE

FIGURE 20. " Total copper content as a function of the weight ratio of ISX to covellite. 15

Selective flocculation tests were con­ The lnfrared spectrum of freshly ground ducted with synthetlc mixtures of covel­ pyrite (fig. 22A) sho'.vs only a sharp band lite and pyrite (freshly ground and at 418 cm- I assigned to S-S (sulfur­ weathered) containing 0.5, 1.5, 2.5, 3.5, sulfur) stretching vibrations (20). In 5.0, and 10 pct pyrite in a total 0.1 g the spee:trum of weathered pyrite (fig. of mixture. The natural pH of weathered 22B), other bands of variable intensities pyrite mixtures was lower and decreased are present besides the 418 cm- i band: with an increase in the quantity of py three bands in the 1,000- to 1,200-cm- 1 rite, Addition of ISX (or NaOH) to these region: one at about 990 cm- I ; and three pulps caused rapid floc formation and between 550 and 650 cm- I . These bands settling of both minerals. Thus the are in the region where S-O (sulfur­ presence of weathered pyrlte causes oxygen) vib~atioQal mod~s in sulfate are heteroflocculation and appeals to inhibit found. T~e b~nd about 990 cm- I is asso­ selective flocculation. ciated with ~he v1 stretching mode. Bands in the 1,000- to 1,200-cm· 1 and in The zeta potential of freshly ground the 550-· to 650· 'CII'- I regions are associ­ pyrite differs considerably from those ated with stretching modes v3 and v4' re­ recorded with the same fines after air spectively. These modes in a "free," aging (fig. 21) Shifts in p.z.c. as that is, noncoordinated sulfate group, well as charge reversal occur in going are degene~3te because of the essentially from the fLeshly glound ~o the aged tetrahedral symmetry of S04 2-.. Bonding mineral. The zeta potentials also become through oxygen causes a lowering in the more negative at pH values above the symmetry of the sulfate group, and splits p.z.c. with increased aging, the 0egenerate modes, If only one oxygen is in-volved in bonding,. the symmetry is reduced to C3v and each v3 and v4 split 50.------.------.------.------.------. into two bands. If two oxygens are in­ KEY volved, the symmetry is further ~educed to C and each v3 and v4 split inro o Fresh 2v three bands (21), Thus, the spectrum of 25 09 rno weathered pyrite (aged 24 mo) indicates &30 rno the presence of a S04 2- where two of its

> four oxygens are involved in bonding. E Karr and Kovach (22) had analyzed the ....J 0 f ar'infrared (50 to 200 cm- I) region of c:{ I- surface films from pyrite--rich mine ref­ Z uses and found the spectrum to be identi­ LU I- cal to that of orthorhombic, anhydrous 0 c.. -25 FeS0 4 , More recently, Brion (11) unam­ c:{ bigously identified the presence of S04 2- I- LU groups on weathered pyrite surfaces using N X-ray photoelectron spectroscopy and sug­ -50 gested that the final oxidation product is Fe2(S04)~' Clifford, Purdy, and Mill­ er (24) had also pointed out that pyrite ground in air showed photoelectron spec­ tra consistent with S as S04 2-. Scanning 75L-----~------~-- 2 4 6 8 10 12 electron microscopy (figo 23) established that aged pyrite is extensively covered pH by another phase and that the surface FIGURE 21. ~ Zela polenliol ofweolhereJ pyrile< coverage increases with aging. 16

A

t z Q en en :E en z < a: .....

8

, , , I 1- ___1 _ __ I I I s-o ,I Pyrite S-S

v,

1,200 1,100 1,000 900 800 700 600 500 400 300

v, cm-' FIGURE 22 .. Infrared spectra of pyrite. A, Freshly ground; 11, 24 mo old.

Weathered chalcopyrite fines were also precipitation and a shift in p.z.c. found to produce more acidic pulps than Covellite and galena samples did not show those of the freshly ground material and a p.z.c. when freshly ground, but exhib­ to form gelatinous, rusty precipitates ited p.z.c. 's at 5.5 and 5.3, respec­ upon addition of base or ISX. There is tively, when aged. Aged covellite formed also a shift in the p.z.c. and a change rusty flocs when treated with ISX or in the magnitude of zeta potentials NaOH, but this may be due to the pres­ (fig. 24). In bornite, variations in ence of some pyrite (see table 1). The zeta potentials and p.z.c. with aging p.z.c. 's of aged sulfide minerals, to­ were also found (fig. 25), but no pre­ gether with the pH n of their pulps, are cipitate formation was observed. Weath­ listed in table 4. ered pyrrhotite also produced extensive 17

TABLE 4. - Points of zero charge and pHn of suspensions of aged sulfide fines

Mineral and age Point of zero charge pH Covellite:

FG •••••• I •••••••••••••••• NO 6.2-6.3 12 rno •••••••••••••••••••• 5.5 5.8 Chalcocite: FG ••••..••••.• 5.3-5.5 7.2 ~4.0 6.0 Pyrite: FG ••.•••••••••••••••.•••• 4.6 6.5 9 rna ••••••••••••••••••••• 8.4 4.9 30 mo •••••••••••••••••••• 7.2-7.3 3.8 Pyrrhotite: FG ••••••••••••••••••••••• 4.9 5.4 30 rna •••••••••••••••••••• 7.3 5.0 Chalcopyrite: FG ••••••••••••••••••••••• 4.8-5.5 5.6 9 mo ••.•••••••••••••••••• 8.4-8.6 4.7

18 rna. t •••••••••••••••••• 8.1 4.7 30 rna •••••••••••••••••••• 7.1-7.2 4.3 Bornite: FG ••••.••••••••.••••••••• 6.9 6.9

18 rno ••••••••••• I ••• I •••• 4.8 6.3 Sphalerite: FG •.••...••••••.••••.•••• 7.2-7.5 6.5 30 mo •.•..•.•••••••.••••• NO 5.6 Galena: FG •••..•••..••••••••••••• NO 5.8 30 mo •.••...••••••••••••• 5.3 6.0 Molybdenite: FG ••••.••••.••••••••••••• NO 2.8-3.4 30 rna •••••••••••••••••••• NO 4.0 FG Freshly ground. NO Not observed.

It is interesting to note that pyrite, particular interest were mixtures con­ chalcopyrite, and pyrrhotite aged for 30 taining bornite since this mineral formed mo in air have p.z.c. values falling in floes with ISX, which could withstand the same vicinity (pH~7.2), suggesting postflocculation physical separations. that the dominant oxidation product(s) on the surface of the three minerals may be Preliminary studies using one-to-one t he same. mixtures of bornite and quartz showed that addition of ISX caused rapid forma­ FLOCCULATION OF SULFIDE tion of large, dark floes, and a whiter MINERAL-QUARTZ MIXTURES supernatant, as seen in figure 26. X-ray diffraction showed that the solids col­ Separations of binary mixtures of a lected from the supernatant were enriched sulfide mineral and quartz were studied in quartz while the floes were enriched to assess the capability of ISX to selec­ in bornite. tively flocculate sulfide minerals. Of 18

FIGURE 23. - SEM photomicrographs of pyrite fines. A, Aged 6 mo; B, aged 30 mo. 19

50 50 KEY KEY Chalcopyrite • Fresh • Bornite 25 25 o 9 ma \J 18 ma > A 30 ma E > E ...J 0 ...i 0 ~ ~ I-- I- Z Z UJ W l- I-- 0 0 a. a. « -25 I- -25 « UJ I-- N W N

-50 -50

-75L-----~----~------~ _75L-----~------L------L------~ ____~ 2 4 6 8 10 12 2 4 6 8 10 12 pH pH

FIGURE 24, - Zeta potenl ial of weathered chal copyrilc. FIGURE 25. - Zeta polenlial of wealhered bornile.

In subsequent experiments, the quartz­ Nonflocculated and flocculated solids enriched supernatants were first decanted were then collected separately and recov­ after flocculation with ISX. The floes ered by filtration. were redispersed in water and recovered by filtration. They were again redis­ For comparison, other experiments were persed in water and subjected to a swirl­ performed using CLS instead of ISX and ing motion to momentarily break up the without addition of any starch (only NaOH large floes. This operation allowed the to adjust the pH to the range of 9 to release of entrapped quartz into the 10). Settled solids were separated from supernatant, which was again decanted. the supernatant either by decantation or This procedure was repeated twice and with the tilted plate elutriator. solids were recovered by filtration. The pH of the floc-containing fraction re­ The results of experiments for mixtures mained between 9 and 10 during washing of containing 50 pet bornite and different the floes. The ISX readily flocculates treatments (that is, using ISX, CLS, and bornite at this pH range. no addition of starches) are summarized in table 5. All recovered solids were In other experiments, the tilted plate analyzed by X-ray diffraction for mineral elutriator illustrated in figure 3 was identification and by chemical analyses employed in postflocculation separations. for Cu, Fe, and Si content. Tests 1 In this case, flocculation was performed to 3 (ISX treatment) established that the in a graduated cylinder and the floccu­ floc fractions were considerably enriched lated and nonflocculated minerals were in bornite as seen from their grades transferred to the elutriator. The coun­ (76 to 92 pet). Likewise, the grades of terflow of water aided in the removal of solids recovered from the nonfloccu­ nonflocculated material from the floes. lated fractions ranged from 83 to 87 pet 20

FIGURE 26. Q Selective flocculation of bornite from a mixture with quartz.

TABLE 5. - Selective flocculation of bornite from quartz

Test Reagent 1 p:I Conditioning Fraction Recovery,3 pct Grade,3 pct Initia::_ Final time, min analyzed 2 Bornite Quartz Bornite Quartz 1 ••• ISX 8.1 10.3 150 F 65 6 92 NAp UF 15 71 NAp 83

2 ••. ISX 7.5 10.0 90 F 65 21 76 NAp UF 10 49 NAp 83

3 ••• ISX 8.0 9.0 30 F 60 11 85 NAp UF 13 84 NAp 87

4 •• , NaOH 8.1 10.0 30 Sd 72 68 51 NAp St 6 7 NAp 54 I 5 ••• CLS 8.0 8.1 30 Sd 70 43 62 NAp

St 2 56 NAp I 74 I I I I NAp Not applicable. 11.5 g of each mineral; 0.05 g ISX. 2F, flocs; UF, unflocculated fractions; Sd, settled fractions; St, solids recovered by supernatants. 3Calculated from analytical data for Cu, Fe, and Si. 21

quartz. The improvement in bornite grade making it difficult to obtain a differen­ after treatment with ISX shows that ISX tial separation. selectively flocculates bornite and that the bornite floes are strong enough to The recoveries of bornite in the ISX withstand postflocculation separations. treated mixtures (tests 1 to 3) ranged The effect of ISX can be even more from 60 to 65 pet and those of quartz clearly seen if tests 1 through 3 are from 49 to 84 pet. They do not total 100 compared with tests 4 and 5. In test 4, pet owing to transfer losses incurred in where only NaOH was used, essentially several stages of washing, decantation, no selectivity (51 pet grade of bornite and filtration. Separation of other mix­ in the settled fraction) was attained tures of sulfide minerals (covellite, and the solids in the settled fraction chalcocite, chalcopyrite, pyrite, and were slimy and difficult to filterr A pyrrhotite) with qucrtz were attempted. slight selectivity represented by 64 pet Only chalcocite and pyrrhotite formed grade of bornite in the settled frac­ distinct dark floes; these floes had the tion was found in samples treated with tendency to break apart during separation CLS. The floes resulting from CLS were procedures, thus preventing postfloccula­ small, fragile, and easily resuspended, t ion re cove ry •

DISCUSSION

ISX forms floes of various strength the flocculation of freshly ground pyrite with a number of sulfide minerals, but by ISX (25). Contribution from attrac­ not wit h quartz. Floc strength may be tive electrostatic forces may also be in­ related to the manner by which ISX inter­ volved in the flocculation of chalcocite acts with each of the mineral surfaces. (zeta potential ~20 mv, pH 9-10).

As mentioned earlier, ISX is particu­ Since repulsive energy barriers be­ larly attractive as a flocculant because tween particles become more significant the xanthate group would be expected to only at magnitudes of zeta potential form covalent bonds with metal compo­ above 14 mv, other contributions such as nent(s) on the mineral surface, as is be­ Brownian (perikinetic) and velocity gra­ lieved to occur in the alkyl xanthate dient (orthokinetic) flocculation, and flotation of sulfide minerals (4). In adsorption energy should be more predomi­ general, the larger and stronger floes nant in the flocculation of covellite, formed with ISX, when compared with those pyrrhotite, chalcopyrite, bornite, and formed by cross-linked starch alone, in­ galena by ISX. For these minerals, the dicates involvement of the xanthate group strength of the bond formed between ISX in the flocculation mechanism. and lattice metal site(s) could account for their flocculation. In those in­ Table 3 lists the pH ranges of fastest stances where cross-linked starch also settling and clarification with ISX, the induced some flocculation, such as with corresponding zeta potential values at pyrrhotite and bornite, electrostatic that range, and the experimental p.z.c. attraction may be one of the mechanisms Except for sphalerite, where best floc­ involved. culation was found in the vicinity of its p.z.c., best flocculation occurred at The fact that bornite forms the strong­ pH ranges above the p.l.C. of the miner­ est floes with ISX also suggests that the als and, except for pyrite, at absolute bonding between the xanthate group and values of zeta potentials greater than lattice metal component(s) is stronger 14 mv. Pyrite and ISX are oppositely for bornite than for the other minerals. charged, with zeta potentials of compara­ While ISX can form strong bonds with ble magnitude (~8 mv) in the pH range bornite and selectively flocculate it where best flocculation was observed, so from quartz, cellulose xanthates appear that some contribution from attractive to show selectivity towards chalcopy­ electrostatic forces may be involved in rite (~-lL). This suggests that factors 22

other than the nature of the chelating pyrrhotite, release Fe(III) species into group, such as electronic or stereochem­ solution. Hydrous ion(III) oxides form, ical contributions from the polymer back­ which themselves are strong flocculants bone, may also influence flocculant se­ and cause heteroflocculation and there­ lectivity as has been indicated earlier fore inhibit selectivity. This may be by Kitchener (1). of importance in mineral processing applications where it is not always Weathered sulfide mineral fines, in possible to deal with freshly ground particular pyrite, chalcopyrite, and surfaces.

SUMMARY The flocculation response of covel­ plate elutriator as postflocculation lite, chalcocite, pyrite, pyrrhotite, separations. chalcopyrite, bornite, sphalerite, ga­ lena, molybdenite, and quartz fines Flocculation of sulfide minerals with with ISX was studied. Best flocculation ISX appears to involve covalent bond for­ was observed for covellite, bornite, mation between the xanthate group and pyrite, and sphalerite. The pH range metal component(s) on the mineral sur­ of flocculation is different for each face, at least for freshly ground born­ mineral. ite, covellite, chalcopyrite, pyrrhotite, and galena. ISX selectively flocculates bornite from mixtures with quartz. The bornite The presence of weathered minerals, flocs are strong enough to withstand in particular pyrite, chalcopyrite, and separation and recovery from the un­ pyrrhotite, may be detrimental to selec­ flocculated quartz. Recoveries between tivity because of the release of Fe(III) 60 to 65 pct of bornite and grades of species into solution, which forms hy­ 76 to 92 pct were attained using decan­ drous iron(III) hydroxides at pH )3 and tation and washing methods and a tilted cause heteroflocculation. REFERENCES 1. Slater, R. W., J. P. Clark, and 6. Brown, E. H. Concentration of Ox­ J. A. Kitchener. Chemical Factors in the idized Iron Ores by Froth Flotation in Flocculation of Mineral Slurries With the Presence of Carbohydrate Xanthates. Polymeric Flocculants. Proc. Bri. Ceram. U.S. Pat. 2,629,493 and 2,629,494, Feb. Soc., v. 13, 1969, pp. 1-12. 24, 1953.

2. Kitchener, J. A. Principles of Ac- 7. Brown, E. H., and T. A. Cecil. tion of Polymeric Flocculants. Bri. Concentration of Sylvite From Sylvinite Polym. J., v. 4, 1972, pp. 217-229. Ore. U.S. Pat. 2,699,255, Jan. 11, 1954.

3. Attia, Y. A., and J. A. Kitchener. 8. Wing, R. E., and W. M. Doane. Re­ Development of Complexing Polymers for moval of Heavy Metal Ions From Aqueous the Selective Flocculation of Copper Min­ Solutions With Insoluble Crosslinked erals. Proc. 11th ht. Miner. Process. Starch Xanthates. U.S. Pat. 3,979,286, Congr., Cagliari, Italy, 1975, pp. 1234- Sept. 7, 1976. 1248. 9. Removal of Heavy Metal Ions 4. Poling, G. W. Reactions Between From Aqueous Solutions With Insoluble Thiol Reagents and Sulphide Minerals. Crosslinked Starch Xanthates. U.S. Pat. Ch. in Flotation, A. M. Gaudin Memorial 4,051,391, Sept. 27, 1977. Volume, AIME, v. 1, 1976, pp. 334-363. 10. Swanson, C. L., and R. A. Buch~n­ 5. Chang, C. S. Substituted Starches an. Acidimetric Estimation of Xan­ in Amine Flotation of Iron Ore. Min. thate in Starch. Staerke,. v. 30, 1978, Eng., September 1954, pp. 992-924. pp. 206-207. 23

11. Friend, J. P., J. Iskra, and J. A. 20. White, W. B., and R. R. Rustum, Kitchener. Cleaning a Selectively Floc­ Infrared Spectra-Crystal Structure Corre­ culated Mineral Slurry. Trans. Inst. lations: II Comparison ~f Simple Poly­ Min. Metal. Sect C, v. 86, pp. 235-236. morphic Minerals. Am. Mineral., v. 49, 1964, pp. 1670-1687. 12. Zeta-Meter, Inc. (New York). Zeta ·-Meter Manual. 1975, 139 pp. 21. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination 13. Riddick, T. M. (publ.). Control Compounds. Wiley, 1978, pp. 239-242. of Colloid Stability Through Zeta Poten­ tial. New York, 1968, 372 pp. 22. Karr, C., Jr., and J. J. Kovach. Far-Infrared Spectroscopy of Minerals and 14. Yarar, B. Physicochemical Inves­ Inorganics. Appl. Spectrosc., v. 23, tigations of Flotation and Selective 1969, pp. 219-223. Flocculation of Minerals. Ph.D. Thesis, Univ. London, England, 1969, 232 pp. 23. Brion, D. Etude par spectroscopie de photoelectrons de la degradation 15. Selective Flocculation as superficielle de FeS2' CuFeS2. ZnS, et a Mineral Beneficiation Process. Pres. PbS a l'air et dans l'eau (Photoelectron at 2nd World Filtration Congr., 1979. Spectroscopy Study of the Surface Degra­ Filtration Soc., Croydon, England, Pre­ dation of FeS2' CuFeS2' ZnS, and PbS in print, pp. 317-331. Air and in Water). Appl. Surf. Sci., v. 5, 1980, pp. 133-152. 16. Fuerstenau, M. C., D. A. Elgil­ lani, and J. D. Miller. Adsorption Mech­ 24. Clifford, R. K., K. L. Purdy, and anisms in Nonmetallic Activation Systems. J. D. Miller. Characterization of Sul­ Trans. AI ME , v. 247, 1970, pp. 11-14. fide Mineral Surfaces in Froth Flotation Systems Using Electron Spectroscopy for 17. Fuerstenau, M. C., and B. R. Chemical fulalysis. AIChE. Symp. Sere 71, Palmer. fulionic Flotation of Oxides 1975, p p . 13 8-14 7 • and Silicates. Ch. in Flotation, A. M. Gaudin Memorial Volume. AIME, v. 1, 25. Healy, T. W. Principles of Dis- 1976, pp. 148-196. persion and Aggregation in Beneficiation of Mineral Fines. Ch. 12 in Beneficia­ 18. Sontheimer, H. Flocculation in tion of Mineral Fines, ed. by P. Water Treatment. Ch. in Scientific Ba­ Somasundaran and N. Arbiter, Soc. Min. sis of Flocculation, ed. by K. J. Ives Eng. AIME, 1979, pp. 161-178. (Proc. NATO Advanced Study Inst. on the Scientific Basis of Flocculation, Christ 26. Sresty, G. C., A. Raja, and P. College, Cambridge, England, July 3-15, Somasundaran. Selective Flocculation of 1977). Stijhoff and Noordhoff Interna­ Mineral Slimes Using Polymers. Ch. 8 in tional Publishers B. V., Alphen aan den Recent Developments in Separation Sci­ Rijn, The Netherlands, 1978, pp. 193-217. ence, ed. by N. N. Li. CRC Press, v. 4, 1978, pp. 93-105. 19. O'Melia, C. R. Coagulation in Wastewater Treatment. Ch. in Scientific 27. Sadowski, Z., and J. Laskowski. Basis of Flocculation, ed. by K. J. Ives. Enrichment of Mineral Mixtures Containing (Proc. NATO Advanced Study Inst. on the Sulfide Minerals, in Particular Copper Scientific Basis of Flocculation, Christ Sulfide Ores. Pol. Pat. 93,247, Dec. 15, College, Cambridge, England, July 3-15, 1977 • 1977). Stijhoff and Noordhoff Interna­ tional Publishers B. V., Alphen aan den Rijn, The Netherlands, 1978, pp. 219-268.

~U.S. GOVERNMENT PRINTING OFFICE:1983-605-015J79 INT.-8U.OF MINES,PGH. 1 PA. 27 iSB