~,-"""-,,, .-

530

,"Selective flocculati'on is an importart techn"K11.:e for prccessing

fine and colloidal par1icu~tes d:Jring mir.eral separation,and for the manufacture cf h~h j:erformance cer8mic andelec-.ronic materials. In sp,te of signIficant progress rrade in

the understanding of t~ fundamentals inv;)ived, indua:~aiapplication, cf this te<:hnique have been rather Im~ed,ori1lariiy as a result of the lack of seleC1ivity ot separa:ion.

AdGrM88~gnUr Cder for Cdloid, 3I1d k1t,rfecN. Henry !<r'.-nb S:;,~~ 01MnN. Columa Uni'i8f'sity, SCO W..t12Oth Street. 918 S\V \tlldd

Bullang. ~ Xork. NY 1 0027. USA

t.omail; pa248coll..1lbie..wtCOlJXftt8 Res~ Center, Wemat~ P~.. Long Meldow

Road. Tu*o. NY 1 0981. USACQ(r8spondence: P SomaI\:nd.,a,1Current Opinion in Colloid & Int81f8C8 se:ence 19ge, 1 :530-034

C Cu'Tent Sc;e"ce Ud :SSN 1359-02~

Theoretical considerationsThe succcss oi sc~arttion by sciec:;...e ~occulatio:1 ce-pcr:ds on tl-.e libera:ion and dispersion of diffcrin~parciC1;iate materials within a dispersion from c~c~ :)ther,?r:fer~:\rial ad$orption of d:e ftoc::ulancs or. p3fllclc$ ofin:c:e5t. bridging cf the ftocs by tl-.e adsorcec ?ol'fm~rm,leC"Jiei, and eifecuvc s~par1cion of the rlocc'Jlar.edmiSS f-:om th: suspc:,.!ion without r:dispersio:". of ther.oc3, Prefcrential adsorption of a polymeric :eal~nt in :1ccmplex system de?ends 0:1 ~ ir:terflc:al potcn:ial ofthe particle. fructional cov~nge of :he ~r;icl: ,.Jr:acc b-:-.d:c fioccuiant. and :he ::herni~al ns:ure ot" the l1.occulaC1tand the part:culate solids. Forces responsible io~ tnc:~dso:ption of ;.h: polymers on tr.e mincral !urfacc~rc~ulc primar:ly from three types of :>or.din:. name!,!'c~ecttOSta.ic. hyd~ogen and covalc:\t bondl!1g r~ 1. The50:utOn chem:suy ccndiu"os, the rheology of .hc 10lidsui?Cr~ion and the ?o~yme~ prope:ties jjctate thc natur~I)f :hc interactions: several mcch:\:tism3 often operate ~t

tl\: iame time.

-

f

s.ledtYe ftoccuIetion ~ur.d8l'a/\. 0.. and YII 831

irr~vcBiblc process, particu;arly in the dilute suspcnsicnsoften encountered in the Rocx:ulation s!'tcms. GeDera:I'y',the residual concentration or the polymers in ~be systemis onJy . fraccion of :he initial cxncentrltion, thcrcb!suggesting a Stroni adsorptIon affin:ro; of thc polyme=s ontn= ~rticlc surfac~s.

at t ir isoeJeCtric points and any exc:ss char:c resultingfro the solution conditio:1s can Icad to an extend(:dco formation and interpart:cle bridgini.

KiI1atJc 8Spects of ftoccul8tionA .umber of variables involving thc yclymcr-suspendincmQQium and chc piruclcs arc believed tC affeCt the k:nc:t-ics/ot the pol)"tncr adsorpcon on solids. The kinetics of rocad~rpaon of polymer molecules 01: a surface is &OV~m~dbY~c rates of diffusion of thcsc mo:ccules toWirds it. T:te~cion cht.mj,ay condit;ons and t.'te pcl~r propcrCC:s,ind1uding the molecular ~-ciibt and ccnformaao:1 of t!\epolymer, its dosac= and the tempera:ure. are .orne ofth~ ii'Dportant parameters which gover:-. the diffus:on l:tdad.orptior. of polymer on a surface. P.:tide ruorphoic-gyan~ surface chemiCtl properties of to"1C folic also con:riollteto It.~ kinetics and eXtent of Idsorpcion.

Thc Iroain mec~r.ism f.)r polymer.jnduced ftocx:ulatJonis interparticle bridling. which oc::un when segments ofthe pol~mer chain adsorb onto mor: thaT. one particle.~Jln~' models have been developed (4J co calcuJa:e :h:collisior; cfficiexy becween tWo particles. Factors thatar~ .considered to affect the collision efficiency, And thwfiocculltion. include :he siu Ind SUrflC: active siteJ ofparticles. molecular wcight. adsof?tion denJity Ind L""\econformation of thc po)~-mer It the interfaces [l,l).

1ie dyr.amic aspeca of polymer acsorption and ftoc.:u-1a~o.'t have been discussed in the )jte~ture. Grepry [8)vllualir.:d adso:ption ~nc nocculatio:1 St-~s as collision~rPc:ssej which may be eicher due to diffusion Gf pol~-mermp\ecules (rapid adsorptio:1) or incuced b'j' d-.e motion oft* ftuid in the fYJtem (s:O\\' adsorption). Lec snd GreCOr;'['4 stUdied the effect of cha:"cc cGnsj~ ano molect:lar~ss on the flocculation kinetics of silica susper.sions, :ondf~nd that the r8te of polymer I.copolvmcr of acrylarnideand dimet.""1ylaminoeth~-1 acrjlltc) adsorpti:>n c:>uld b:slbw compared to the particle collision race w~:n low~arge densities and \0\\' molecu:ar mass po!~er ~-ere\:.ed, Using I simple technique ir.vok'in& immersion ,>f ag1ass plate in cationic po:~mer so!utions (or sho:t per; odsf~liowed by deposition of silica spheres on the adsorbedpplymers, Sivakumar. Onoda anc I have shown [10.11} :hat~e adso:p:icn can be cooplete in :ess than on: minute,1. fact there was Ye~' litrl~ ads.1r;>tion durinc :h~ first fe\\'seconds folJo~d by a '~Itastrcphic:' $udden increasc in

a~sorpcion,

Effect of v.nabl..Pretr..tmentFIOtt'Ulation can also be enhanced or pm'ented ~ meaddition of' ions ~"hjch, either by compctiri~"C Idso:p:ionon L'1e min~ral surfa;=: or by compleXln& ~th polym=rs i., t.~ bulk. can cause activation or inhibitior. of theprocess. For eurep!e. selective Do;;culacion ol hematite-quartZ mineral ciyltals usinc anionic pclyactytamjce hasbeen r:ported ro be effeCtive with the addition 0: thedetergent Calgon8 and sodium ft'.JOride {5}. Treat:nent'Prior to ftOCt:\Jlatlon may consist of comminutio'l .ndliberation of const1tuen~ compon=ntS. mcchanical andchemical dispersion, and anT ot."1er proceu co re:novepossible coatin& ma:ter (6]. Additior: of polymeric d:s-persan:s :s often found to be necesary to obtain fullliberation of the componenu in the suspension. bl;tpol~'mcr-pol~-mcr interactions can aJlC have detrin:en:aleffeCts on subsequent flocculation. Fun.'termore. not onl~'does the conc~ntration of the dispersant have a markeCeffecr on sclecrive flocculation. but also the modc oi itsaddition (introduCtion of the dispersant before or ar~erthe grinding stage) can markedly affect the aggr:gaticnbcha,-jor of ?Mriculaces.

$eledlvlty, or the lack of ItSuccessful sep~rttion of real mine:'lls and ever. of~~theti:: miXt'.Jrcs of pure r!\in:~i ccmponentS often :'ai;s;;tlis has been attributed to the eostir.g or impurit;cs onqne o. more solid surfac:s, Such impurities, owing !och.:ir adhesion ?ropcrtics. ate called cemencni :nate~ials,~cmo-.-aJ of such coatings ~Dd o~ga:1ic cemendn& matrriauhis been .fbU!1.t;1 t~, :r.bancc s:lc::c:ve separation off:an::olice from pho'sphat: slimes sig:1incandy (6). Loss4r sclccti\"icy is also caused b~ .sli:ne coating', I phc',omenoc frequcntly en::ouDtcrcd-in narwal o~e systCR".~,nd '-'"hi. is charaCterized by the presence of a numbe~If hetetoce:teous co:utiruentSo Dis:)eBsntS can be uscc, -~ prevent such 'slim~ coatin&' anj 'heccroco&&u:lcion'o!"he main criterion in thc sclecrion of such dispersants isjninim~m intcrference \;pon lubseq"Jen~ Adsorption cf t1:c

rOCCula:tu,

Surf8ce coverag. aM Its InfI\Mne8 Oft ftOCQll8tionThe conditioaing (mixing) ti:nc of the minera! "iththe pol~er :ovcrns the extent of surface coverage.Frolor.:ed conditioning resultS jn redispcrsion cf theparticles possioly due ro saturation CO"1cr&ce of the pir-.iclesurfac: b.," pol~-mcr molecules. Stcric srabilization, d".1e toccmpletc co~erage of the particl~. results from chan&e$in tbe er.uopic and enthalpic components of :he freeener~' due to thcc intCrpeneua:ioD of polymer chains;inccrpcnc:ration in turn depends on thc interaction,of th: poJ:'mer WIth thc lol..cnc, as ~'ell II cn thedissol\ocd ir.organics in the ~.,tem. The role of poi)"~erconformation is also very important in the interparticlebridging mechanism (7-) Ext:ndcd chains of pol~erlhsve recentl~. been fuund by Yu and I to be more ~f:ectjvefor bridcing. CoiJin& of pol.,-mcr moleculcs is max:mu~

COOIJ! ~~nTA .T-\~n~ QltQ nQ~ tlTn TV.4 lZ:QT ~. ~8 TOiTf

AppliQtions In chemlsv., I chemical engineering532

formed loops and tails at the latex surface and BOCC\Ilatedthe latex particles by bridging. In contrast. polyrr,ers withhigher charge deMicy adsorbed in a fiat connguratiot\and fiocculanon occur~d by charge neu:ralizauon. Theyfound latex particles co acquire a high positivc char&cat maximum adsorption of h;gh:? charged polymers. The~uthors ~rgued tha: since d'.e mean distance 'DetWeenpositi,c charics on rhe polymer ,vas smaller than t:'edistat\ce becweet1 the charges on the lace., particles. icnicbindit1g of the polymer ro the ioniz~d latex surface groupscould not cakc place w::hol:t sin-.uicaneous attaChment (Ifan excessive positive c~argc to the lateX surface.

Polymeric reagentsPolymer molecules can -sel~ctivel!, adsorb on minenlsurfaccs by appropri,ate adjustment of the suspendingmedium ,vhich controls the charge density, b~' theintroduction of chelating or ocher s(litabl~ functinnalgroups on :he polymer, and by use of inhi~itors 'Which atedesIgned to preVerlt adsorption of the pol~mcric 8occulanton unwanted minenls. Starch and related polysaccharidesba..-: been ,,;dely applied ;0 tho:. mineral p.-ocessing in-dustry as depre~$antS, ftocculantS and selective flocculancs[11). Modific3u.'>n of starch and other n;1tun!. polymersi3 carried OUt by substituting different functional groupsintO the poi)-:ner chain. Numerous mechanisms havebe~n propos~d for the adsorption of starch and relat:cpol,,!saccharidc, onto parccles. Hydrogen bonaing andhydrophobic intenctions becwcen pol~"Sacch2rides I:1Cparticle surfaces are mainly responsible for th: adsorpt;oQ.Other cvide..ce, however, has ,bawn chemics\ interactior.salso pl"1Y a significant role [131.

Recently, Ravishankar 1181. [1S.] invcscilatcC the seleccivc80cculation of iron oxide from itS Ir.ixcur: ~-ith cla)'S usi:\gcommercially available potyac-;:lic acid and starch. andfound the rcquired 6oc;;ulant dosaie far polyacryiic acidto bc lower than chi: of starch: ho,,'cyc:, starch appearedco be more selective. Mecna:1isms based on binuc:le~rcomplexation of $tlrth wid-. iron sites on iron oxjdc andalumi~um sites on a!umina surfaces were proposed [IS.]to explain the findings.

Polyacrylic polymers arc ,tiU the main type of polymerused in flocculation and icleccive flocculation process~s.Synthc:uc tlot:1Opol)-m~rs become ~ffcctiv= selective foc-culants when functional groups are incorporated into thepolymer backbones. Yu and I [14] have observed enhan~c!ftocculation of a.lumina \\;th double nocculancs: \vhilcneither pol~t)-rene sulfonate no. cationic .oolyacryialI'ideshowed app;cciable flocculation of alumina ~'hen usedscparatCl"Y, cxcellcnt flocculation wu obca:ced when boa-.of them we;e added together co the s?Stem. \Vc propos:d[14] thac al'.Jmina particles with preadsorbed polyStyrenesulfonate fiocculatcd as a rcsulc 0: bridging by the catiorucp.,lyacrylamide.

In a related investigation, Jarnscrom If al. [19-] 3tudiedthe eocculation ofkaolir. suspensions induced by mod:ned'tar~hes by mcasuring fluctuations in :hc tUrbidit"f inftO\\'ing 5uspcnsicns using a fiber-optical scnsor. Th:'ffound mar i cadonic~l1y ~ocined starch \nS an excell=r.rftocculanc. e\"~ at vcr"!" low ao,alcs. F:occulation msgood ;f the ionic srrc:1gth W2S maintained becwcen1 and l00mt.1 in the tcmperarurc interval Z3-30'C.Interesandv, ftoc~ulation was poor at 1 mM NaCI cor..cencration when d-.e kaolin suspension wa3 pretreated\vith Na-polyac;-yiatc. The flocculation was satisCactOr;' inthe prC$ence oC Na-pol)'acrylatc at higher slit and starchconcentrations, howeve:-. 0:1 the basis of adsorption ex-pcrimenu, thc authors suucstcd thc cationically mod:ncdand co!lverted starch to be nocc:1:ating kaolin by bridging.

Reccntly. Wci~scnbom t/ ill. [158,1681 have swdicd indetail selective ftocc".1l a tior, of ultran:\c iron ore usingstarch and its arny!op~in and amylose comPCJnencs. Usin~diffuse fcfte::tanc: infrared FOUriCf uansfonn (DRIFT)spectroscopy and merrnogra..imetfic met."\ods, these ~u-mars found wheat starch ar.d amylopccri:1 tc stror.glyad30rb onto iron particles. Adsorption \\.35 due to theformation of a surface complex rather than hydrogenbonding. The preferential adsorpdon of starch on[ohema[ite rather man kaolinite \\'as attribut:d :0 tr.e higherconccntr.tion of hydroxy!ated metal adsorption sit:s onthe iron oxide ;urt"ice compared with cr.e ccnce:\tratior. onkaounite. It ~"3S interesting to note that >95% recover-,'of nematite occuircd a: !f)W frac:ion3.J surface coverage.- 0.2-0.6, and at low iesiauai Sta~ conc~ntration. Theauthors prcp05ed the classical bridgir.g mccl-.anist:1 toexplain 8oc::ula:ion.

~{oudgil t1 6/. [20-) havc rcce:1t!y arricd OUt sclectivcftocculacion of dolomite minerals ha\;ng similar chem:calcomposition and cr)"Stal stroct-.:re but of different surfa:::properties, by using polyethylene oxides. \Vhilc usc ofpolycthyicnc oxidc with a molccular wcid1t of five mi:lionDaltons. as a ftocc\:lant resuit:c in 10S$ of selectivi:v,preadsorption of a low ~ol~cular weight (100 000 02.)po!yc:byicnc o.1C.ide biockcd acc;vc adsorbing sitcs and thusminimized hctcrocoigulacion and yic!ded I near ccmplet:scparation at pH 10.5.

Sh~r ftoc::ularioD of mi:1cral fin=s involves hydrophobizo-cion :)f the mineral surface by a suitablc :ollector fol1owedby formation or aggrcgatcs of thc ~.nc particl:s by stirrir.g.A recent shcar flocculation attem?t was made by Akdem:r:and Hic,!llmaz (21J. who usec sodiurr. oleG[e to modifythc hydrophobicity oi chromitc tina. Rccen[ly. It.: andI [78) discussed the role of polym~~ conformation in [hc6occulacion of alumina witt', ~ dual poly~er combination

In 8 study 00 th~ flocculation of ne~'2[jv~I'i chargedpolyJt!rene lat~x particles using cationic modi5cd polY-acrylamides. Eriksson II oi. [17) chose conditiOn~ s~r.that polymers approoched an equilibrated adsorption StatCbefore appreciable ftocculacioll took piacc. It Wl' menobsel\'ed ~hat polymers with very :ow chargc density

" c,

.nn'"

: ;;:;"::;~t:~f;';~

~"'..

~li'l~~.SeJectM ftoccul.t~on Somas".,dar-an. Du InC "',j 533

(polydialty! dimcmyl ammonium chloride and poly-acryiicacid). \\'bile polydiallyl dimethyl ammonium chiorideftO(;culacion was found to be governed oy polymer bridgingat high pH. the ~cct-.2ni!m at low pH ~-alucs wascha:-ge neutralization. We scudi:ci the rolc of po!ymerconformation by isolating the electroSt2tic effectJ undcrconsunt zeta potenti~1 conditions. We oOscr.vcd that mcco;:formatior. of tpe- 'tldsorbcd poly:ner molccul~s at diesolid-liqui:i intert-2ce ca:1 be drastic:2lly changed oy theaddition of a secondar)" ~Iymer. anI.! p! changing solutionproperties such as pH. .\n anionic:pol!'rr\cr in stretchedform was found to prO"id~ bett~r in[C~rticle bridgir.gwhc.'\ adsorbed on alurni!\a particlcs with prcadsorbcdcationic pol~'mCr.

2. Yu X: P\QC"".uon .1d d~1on of SUSpenSION by~ntJOmns 8cscrplion. ~gnformetion ~ orlent8t:gn 01porymers [PhO TI\..;sl. ,~8" York: COIUft'bie J ,.it>: 1996.

3. M~dgil 8M. So"...unda~ p~ Aes.arch needs h noceuatton.In Floccufalio/l. S.d';T:entleor. i1Id Co".of/G'atlOn. Ed!,~ byMoudgR a..1. SolT8Sundaran P. New YCri(: AIOhE; 1987 5e1-598.

.. MOIIdgii at.!, B~I S: ~occul.tlon in soIld-aqUld s.p,~"~~~II.'. In ,&j~~ Scie"~. 4I1C !'.",.I:ee.'"#1g. Eaite-j by \1atisKS. N- Yo~. ¥ar=el Dekker Inc: 1 995:41.5-440.

a. Read AD: The lI,e of high ",oleC\lI8' weight polyaoryiemid..in tile ,e'ectiYe t\occ;ll,tioll '8par,tion of a miner,' ~xa.,r..Polym J 1e72, 4'253-259.

8. And8rMn Js. S~ran ?: Mechanisms detarmltin9.aper8tton of P/\osph8t1c Clay _te ty seiectlv. ftocc~laij~.Mi"... M".n"fg .c.roc 19$3, 10:200-203.

Conclusions: .

Prncessing of fine valuabie minerals and ce:amic $uspcn-$ions by selective 1i~lat:on i$ I promising technique-Over the ).ea~s, there ha'-e been many 8ttempt$ to exploitthis technology to achi=ve $elective $eparstion, Becauseof the enormo\;s complexicy of systems, arising fromintet3crions cf the various process paramr.cers, indus:rialsuccess has been limited to one or rwo cases. Thefactors governing adsorptionif\occ:1lauon 0.'1 be re!gtedco the characteristics of the solids (particle size. shapc.morpholog)'. solids :oading. surface potential and charge)."be $olution chemis~' (?H. ionic strength, dissolvedmc:al ions), (:olymer pr:>pemes (mclccular w:iehc. charle

.density. functional voups, dosage and conformation) andhydrodynam.ic ::ondicions (agitation). While much \vorkhas been donc on many of these prop~rties, the mostpcwerful variable. namely, polymer confo:-rnation. hasreceived atcentior. 01".1.,. recendy. It is still not known whichconform~tion will b.: "ptimll for ftoccuJltior, or dispo:rsionof various s~'Stems. E ffor:s should be dir:c:ted firSt co\vardsgaining fundamental und~rsunding of the interactions ofm= difTcrenc parameters invclvcd in selective adsorptionand desired conforn-.au:>n of polymers, and :hen to\vardsappropriately modif':ing ~e process parameters "° achievesclcc:ivicy in separation of rcal ,ystems.

1. V" X. Somuunda:1t1 P: Rd. of polV~ coftfatm8tlon in. Imerpantdl'II"d;~ domlnatad ~o::w8tlon. J CofcJO '"It'rla:e

Sci 199t. , T7:283-287TII. ~iC8 d poI~.r COr1Ofmlt'cn8 :h...g., 0: a ..ri.. ol :~":f "ydtc.Iyt.d pQy8Cr)lamidea ad.c~.d on wm"a ". ~"80U. 1O..1a1."'" I("C-ied 810118 with N f!dCQl!ation r88pons8. It W&8 ob8 ~ ~.I ~c" !;..-d pHcondition. tn. 'locculaticlI ~linuo~ cect_ed 81 a 'I;netk)n cf *nj ~UIIe ~c tI'.akege: ~r snifl8d pH concltionl (low :0 1j91) Ih. ~C\;i8Ii:npUles bough. maxi""", &8 . fl:n~ of t~. du. to ci'I...,get if' x~.,conforma.'ion. u Itucied by l!Ua'eKence tpectrolCCp/

8 Gl8gCty J: PolYMer Idsorpdon Ira 'oc..-v!8IIon in Ih..r.cIVIPenslon.. Co!J~iCJ S"rfac8 1 eee. 31,231-253.

t. Lee Sy. G~ory J: Th- 8ff8Ct of char;- d.n.i~ .n~ mol.C!:I"ma..o' eationi: polymers 0" f10::ui~0II ;or.tics in .que~ussolution. VI.,., S"':ply 19i1. 9:1' -'~.

10. Scmasund¥8f1 P. $i".."umar A : Short term kinetics ofpolymer .dtorptlcn on stesl ..t:str.te. CcJ/oid~, 19.~8.30:401-404.

OtlOda GY. S~~:Jn~ P: Two .nd gne dimenslon81nocculetion of ,Ulca sphere, on ,uo,uwtes. ; CQ//~;c '"renaceSc;1987.11':1S~-175.

11

12. W8i.,er.bCM'n PI<. Wa.-ren u. Cum JG Cptmlslllon o~ I.~ectlvetIocC\llrJo~ of ultr8fM Iron ore. Inr J MI"er Proc ~ 994.42:191-1S8.

13 Lulcow.l<. JS. L'u Q acti" NJ: Poly.."harldl' in tlot8tlon cf,ulphidl" Pitt I. Ad.orptiO" of cciy..ccharici. on:O ,"TIiner8'.utfac... /"t J .""in.,~: 1991. 33:223-234.

14. Yu X. Somuurcaran P: Enhanc8d :'Igccul8tion wi~ doublenoGCUI~t.. Cgloid $udace A 1993. 61:11-23.Acknowledgements

The authoR xknowlcdce the ftnar.cial !Upp«t of tile Na:i()naJ Scie~=Fooodition (I/,;T .WI5417. CTS,~~'ll'1o!(I) lrod mc Encjnccring Rcsc~rcilCClXcr . P21t1Clc Sciencc and Tcchnolo;y. I.:nivcnitr or Florida, grsr.r. ;-14-451. Therc 'vcr: Vet\" few ~apen In tne sr.. oi sclel.'ti..'c ftoccul2:ionr-(~ 1~4 ""wards. Most ,,( ,he p~pol$ tl:fcncd to III tIIc text "",u:c ~e cf.pecial intcra$t :0 tile ~c..-n.

References and recommended readingPapers ~I ~'cuIar i"ternl. pu~.i.n.C .~tt1i" ~. II1n\J8 period of '8'1'-.hive been ~iQntgtlted u:

. ot s~c,.. ilt.-ea:.. 0; outstan6n9 interest

15. W.i..."cOtn FK. W- U. Cllrn ,G Selectlv8 lIo:C\J~ 01. \I/traf". iron ore. 1. Mecn8nism ot adsorp11on of sta.ch Ot'to

hem8tlt8. Co/Iaio S:JtfJce A 1995. ":' 1-21.T'Ie ~'In~m of 8dso~licn 01 wheat lta.-ch 8nd tl cor=cr~n:! on:ohlmalile U8 ftvestigated ty dilf..$i't. r:1!,~.-,co 'nirered ~u~cr ,fInS'101"" (DRIFT) Ipedrca=py. ~"eSt .atC" erd &"~'opectn w.rt ada,rtlecs:rongiy arb h_tile ."d :he ~.uila ",er. '=Cn$8I8nt with ,;he 'c1T"a:.or-. a:a .url- comple

15. Wei..entcm PK. \~8T8" u. 0",,1' JG: S8lectiv. "0~18Iio". of ultrdn. I~ or-. 2. M.ctl8nisrn 0' selective .10=1I18IIon.

Co/hid SuriRee A 1996, H:20-~3.Mectlel'i&me of ...et;.,. ftocculation 01 'e~:e frcm kaolir.iI8. W11i.:.'1 ..-s:alch - tn. f!occuI8nl. Ife OitCtl...j The p'1!e-et;ti8 adsO~laI OJ! -;!ltdtonto Pl8II"8tit. -. pfOposeci :0 bl due m :.,. rnQher concentralio, cf tyaro.cylattd metaildso!ptiOJl1 .:e~,

17. Erikaaon L. Am e. St.,iu. ~: Fom8:iOl\ 8nd smdu'l ~poiysty- latex ea;r~8tes obtained ~) fioCCtl8l1~with cationic polYlledfalYteS, 1. Adsorption anI: aptimllmIIOCC\lI.tian conce"trations. Colloid S,,:iaco 4 1993 70,.7-60.

s.,.,1 s. \1ou~ 8M. F,akuh rs: Control of .ctive .itu 1ft..lectIve flocculdon. I. Math_aVca' mod84. J Colloid Inren&caSci 1993. "'l.14~21.

,.

0: :.';',:~':..:.r;;

.1~mn'" 'N~n~ Q~.Q nQC T1Tn TV~ nr:QT nq. ~R Tft/T~

e34 AppIic8llanl In ~Wy I dlemlC81 .v_line

. .. ~k8t SA, ~ ~. HI<; S~ ftocculdOft of. ~ oxId8 f"'fn liS I~ rra.v.. wIth d8Y8: . 'lw.-18cxtof ~ 8dd 8M I~ poly!--. W J M;". PtOC 1'".Q:235-247.

The ~ of poIy8CIYic ~ (PM) ~ .~ AI ~ ~n 1M ~dallon of itOft «e alWII.. . cOlllO¥'C1. 'M1i1e PM yoeld' ftOQ.. b " doug-. ItarciI i8 !ou~ :0 " ~re ~I Q. .-utroIOIl. ~ L. Rlgdahl M: Roe~"doIIln boll". IUIpeII8IO"S 1"d\.c8d ~ rnod~ iWctI... 1. C8U~'

~ 8t8lch - 8ft.- of ta~-- ,nd ~ strenvdl.~ SiI.-:.ce A'~ 104:191-205-

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