Reprint~d from S.~l.E. MineralProcessing Handbook, Societyof Mining Engineers, New York,New York, 1985.

Experimental Techniques In flotation Ba8ic Research

P. SoNAStJ!lDARANK. P. ANANTHAPAOMANA.HAN

f8UM8CdO8

Small-scale experimentS usial sinlie minerals add pure reasenumay yield impOt'taDl infomwiOll about nowiOll. eYeD lhoup prob-'-s often arise in inlcrpretinl!he faulu add in usiallbem profilablydue to !he djJfit;;uhy of COIIIroUinl all tbe relevant variables. For exam-ple. mineral purity often cannot be COIItrolled due to possible contami-nalioa durinl prepantion. Similarly. pH is often difficult to control.panicuiarly if tbe mineral is soluble add !he diS$Oived speciea arehydrolyZ8bie. Another major problem arises from possible oxidalionof fresbJy prepaRd mineral sampiel, ~pecialIy sulfides add tO81. Dueto a variety of fea1OI\S, PC8ibIe variables in ftOtaliOll are numerousand tbcir ~~ innumerable.

However. cardllUy COIIIroUed Iabotatory studies of micro8otaIionaIonl with related in~ properties such as ~ and d~-trokiIICtic propenies can yield infomwion on the mechanism of nota-tion. fn this ~ experimeaW methods tbat are II3aI in ftotaIioII~ alanl with possible ani*ts and --,ry pra:auUons a~discussaI.

M8f8i8I8 Pr ~ 8tiaa

~ pnICeacS are known to be very seasitive to !he pI'escnceof trace impurities as well . unavoidable ic)aS S1ICh as calcium ormac-ium PfaCIII in the plaDt water. It is, theref~ _1iaI torecosaizc the importance of properly cIaIIiIIl the lJ-iale and COII-ttoIlial the ~ of water UId rapau II3aI in conducting thelata. The foIkJwinl ~ have ~ {ouad uscfu1 for amtrolliDlthe ~ of a SystCtll.

Ga-- G~ is extensively II3aI in 8otation ~and unJcsa tbotOucIIIy c1eana1. it -y beaJme a major ~ ofCUlI~~ina~- A recommaIded procedUR {IX" cle8lliAl alassware isas {~ ~ it in chromic acid {OC' I br to remove impurilielsuch as oxide 81-. wall with disIilled water {our to five Ii-. ~in alcoholic potaMium hydroxide (12 8 of KOH. 16 nIL of water.and tile ~ ethyl aicobol to make 100 nIL of solution) for at leastI br to diaolve the. ocpnic impuriliea. wasil with djS(iJled water 10

SAMPLING AND TESTING30-88

0.01,

~'I~ !'-0.05!

O.J.:

0.:"

~'I~~~II ic--"-if -0,

1"1~#~~I~t~~:~~~~1

;- .".'--4---+

~~:"""~

~'"'i-~ '"" L;!: ~:~:'::';:'7r'7:~'~ ',',:.:=:::.,,:.

.- 'l- ...:t:

:::t-:. !

--._~

~~-.::+:'-+---

2.~ 2."1.55 2.60PIG. 92. !

the dissolution m ,Iass. Solubility of silica can be o{ the order mla-OM or more, depending upon the soIutioo conditions such as pHand rate of dissolution. eYa1 at fQXD temperatU~ - Since the COftCa'-trations 0( reagentS in ftotation are m the ume order. praencc msilicate species in such amounts can be expected to have an inftuer=on the 8otation propenies m miDerab under investip~ It milhtnot always be practical to avoid II- contaiJlen but the possibilitym anifacts due to these problems should be re:oani-L Similarly.the use of ~ aMlWnen should be carefuUy evaluaccd {or ani{8(:1Sas they oftat release various organic materials during storage.

P8rifiC8tio8 of Water. Water can be eft"ectively purified i{ it isfree of volatile matter initiaUy DOOJlation of water in the prfSenCCo{ potassIum permanganare is comnt(M1)y practised in order to destroythe organic contaminants in the system. But amines and similar com-pounds can distiU over an alkaline bath and hence another stage o{

to 12 times, 8IId finally rinse it thr= to four times with triple distilkd_. At this st8ICo !be sawaR may be checked for cleanlinessby Ite8IDin&- Unifonn COIIdeasatioo of Steam 00 the walls of the vaae\(without the fonDaliOll of isolated droplets) can be considered a sipof c\C8D1incsa. at \cut with rapect to orpnic contaminations.

E- JJa8Sware cleaned so intensively can still cauae problemsin ftowion cbemiItry rsearch. For example. iD the "case of adsorptionof cationic surfactanta 00 minerals, surfactant adsorption on sacan lead to experimental anifacts and ~ interpl'elalioas. Even~tion of very dilute solutions (say <IO--M) of such realefttaiD JIass containers can be accompanial by a drastic reducrioct iDbulk surfactant CCM1centration. In such cases, prerinsinc all tbe Class-ware with solutIOnS of similar concentrations is ~ended.

A more serious. thouCh often neglected. problem In this reprois the release of silicate species into the stored solution bec:ause of

MINERAL PROCESSING TEST PROCEDURES 30..9

T.w. 29. Co..eded R..ults of ~y U~ Teots

58 -}5.-3 -

EPM 0.040 EPM O.G.s

P1oat ~ Sink~

UI ... 11.1

EPM 0.040 EPM 0.046

FIO8t SiDk ftIet SiDk

0.41 9.2 0.« u

acid dilaiUarion may be necessary." Ion exchanaen are good forthe ranoval of inorpnic decuolytes. but they are known 10 releaseOfpJIic impurities into the system and hence they should not beusec1 as a final Stage of cleaning. A th~staae distillarion can yieldWater with a ~tly low impurity level. Quality of the water 59Im'dIM:ed can be testec1 by measuring its specific conductivity andsurfKe tensioIL A conductivity value lower than 10~ho/cm anda surface Iension of 72.8 dynes/cm at 2OOC can be usec1 as criteriafor -- purity.

ThouIh the use of freshly prcpared triple distilled water (roW)is adYOCatcd. MyseisaT has suaestec1lhat storaae can be usefUl inallowinc the surface active contaminants to escape from bulk water10 the 5\Irface. Water must be removed in Ibis case usinc a tap or asiphon so that surface water is 5ICDtially avoided. In this regard.fO8mina by bubblinl purified --pumped nirropn throuIb rowand taDoviJII the surface layers may also prove bene6ciaI. In factthe foaminl tendency of Water is considered 10 he a better criterionthan thole mentionecI earlier. Bubblina of niuoaea will also resultin the ~ovaI of any dissolved COt; the resultant water should havea pH 0(7.

Even tbe presence 0( trace impurities has been known10 cause anomalous behavior 0( surfactant sotution and so in ~~nl flmdammtals taean:b uae 0( ultrapure reapalS are~mended. - In aeacraJ. absence 0( a minimum in a sun- ten-sion VI. log COtM:etItraUon curve caD be taken - a criterion for surfac-tant purity even Ihouah tbe sampie can be sriU a mixture of twosurf_IS with similar valua for critical micelle concentration.

Use 0( ftesb surf_t solutions is advocated. as solutions of cer-tain reaaents will undergo oxidation (as in the case of oleic acid) orhydrolysis (as in the case oflong-chain sulfates). Stock solutions insudl cases should be prcpared with deaeraled triple distilled waterand stored in a refrigeratOr under nitrogen atmoslJliere.

lnorpnic cbemicaJs also can introduce impurities into a lest sys-tem. For eumpIe, when flotation ~very is stUdied as a functionof ionic -Ith. the eft'~ of heavy metal impurities such as ladwhich O(herwjse is nqiigible may become significant under high con-cen!ralion. In such ~ it is na:essary to check the possibilitiesfor experimental attifacta by conductinl tests, eoa.. with lad addedto ultrapuIC reaaents.

MI-.L The hetefOieReous and complex nature 0( ore bodiesmakes it dilftcuJt to obtain similar samples from dift"erent mines and.in fact. often from t- locations of the same mine. Therefore. ex-care is needed in selectinl samples for fundamental ~

For normal laboratory ftowioo tests materials ia the BRae ofJS to 200 mesh can be used. Size ~uctioa of Iarau samples canbe achieved usial cnfshers or grindinl mills. Minerals subjecled togrindinl may. however. be contaminated with iron in a ball miU,".with alummum in a pebble miU,'" or even with minerals that havebeen broken in a crusher on prcvious ~ In addition. thesample itself can UDdefIO possible physical and chemical transfOlma-tions duriaa grindin.."Zo... From tbe ~h point of view. thesepossible transformations and contaminaliOllS ~ be miDimjzed.Therefore, it is SUgesled that tbe grindina step be avoided if alterna-tive t«hniques of size ~uctioo are available. Ma!eriaIs in the ranaeof JS to 200 ntesh can be pt'epared usina roll cnIShers. For a further~uction ia size. \lie of apae mortal' is recommended.

The crushed product from rolls may have iron-bearinl P8fticlesin it and they can be removed by p8a1 the material thfOUlh ahigh intensity malnetic separatrK. For oKides such as quartz andalumjna, mild acid (pH ~ I.S) ~nl is recIXDmended. In such cases.acid trcatment shooJd continue till there is DO discoloration of theacid solUtion. After leKhina. the mineral should be washed repeatedlyuntil the pH of the W8Sb liquor attains a constant value.

In aenerai. W8Sbinl with triple distilled water and desliminl of

SAMPUNG AND TESTING30-90

the mineral samples followed by wet $(Or8ge in Tefloo containers isrecomnIeIIded. If mineral samples are stored dry, proIonled equilibra-tion ill - (or in electrolyte solutions) may be ~ for somet~ before tbey are subja:ted 10 any wet studies. Mittcr8is may take8S much 8S l,lXXI hr or - - 10 reach equilibrium in soIution."'-.,. CbaaIC in pH of the supemat8Jlt solution or cban&e in zeta poten-

tial 0( the mineral C8I\ be UIcd 10 dctcnnine the ~uired equilibraliootime.

Extra ~ should be taken while storinI oxidizable materials such8S coa1 and sulfide mi1IenIs. It is penJly believed that cnI$binIand JriIIdiJII 0( such samples in an inert ~ will pmeIItoaidatioa of fresh sun-. 011 the other haIId, due 10 the pGn)USIlatUte 0( ~ miIIeraJsIU inlericM' surfaces might have beett oajdized- before such size redUCIion operations. SIOrin& of such materialsin 8ft inert 8bDmpIIcre. ~erably below room tanpa'ature. wiD pI'e-Valt dcterionIioa 0( the -pia by oxidation.~ ~.;adoa. . PbysicocbCl!Jjcal as weD as m«1lhoiolical

cbar8Ctcrizatioa 0( panic:\cs-is imponant in inlerpfetinJ their bdlaviorin proc8IIina systems. ~Iy used physical characterization tech-niqva include size ~y1i5. ~ty, and surface area masurcmenu.Size ~ysis utilll 5ieYC5 C8I\ be C8lricd oot dowtt 10 aboIIt 62S n1ah(24,..). For sinlie minerals, the ledimalwion IJt1aIIce ('-d <XI Stokeslaw of Mtt1inI) C8I\ be used ill the fitter size ranIC. but for IIetcrose-- 6nes pnlduced from complex ora. the CouIta' COUIIler (moddT A-II) is better suited in the nuae 0( 1 10 SO ,.. III the a)lJoidalrattIC of size dowtt 10 o.OS ,.., the UDAL pipeUc cmtrifu&e basbeett f<Mmd 10 perform salisfactorily,'" The BET technique,.steamacid 8dIOr1JCioo technique. and penneabiIity tecbnique (e.&-, FIShersublievc ~Y%a') are -. the widely UIcd techttiq- for _r-iDI the sun- area of particles. - II' The uearic acid ad5OtptiOIItechllique is limited to polar solids, but may be more rdeYaIIt forobIaiIIinl aD inlcrf8cial area ~ 10 surfaCfant molecules. TheQIIaIII8IOrb _tinuous Bow sorpCioa system (BET area) manu{..:-tured by Qu8lllachnxnc Corp. has beett reported to perform satisfacto-rily dowtt 10 about 0.0028 m"l..-

ScaIUIinI dectrOD microItaPlI$ C8I\ provide val~e informatioa<XI the morph(josy 0( panicl~ which can be imponant in determin-iDI bdlaYior of panicles in a number of mineral pfOCes5iD& opera-nons.

In addition 10 such physical characterization, chemical analysisof particles is also oftaI conducted. Wa attaIysis by classical ted!-niques Ii- bulk compositi<XI of minerals. In S(XDC ~ bowever,surface cbemical composition can be more rdeYaIIt for ftowi<XI re-~b, 8$ the mineraIOIicaI beIeroteIIeilies of samples may resultin Iarae varialions in surf.ce compositions from bulk valva. ~tstudies of hematite samples by tbe AuleI" and EDXRF tecbttiqua-sbowai 8$ much 8$ ~ silica <XI the surface. 8$ ~ 10 thebulk CCXStCDl of S", This dift'aace W8$ in fact UIcd to explain thelower isoeIecuic point of the sample 8$ ccxuparai to that of !be pure

bcmaUte.-T~ such 8S uaer.- eJecuon spectrOIcopy for chemical

attaIysis (ESCA),JI1 iCCI scaIterin& spa:uoscopy in comtXttation wilb.-Ind8rY i<MI - 5pa:tn18CopY (ISS-SIMS),- scaMiDI aucer mi-

~y (SAM)," aDd 5C8DDiDI dectnx1 milCrwcopy (SEM)DI arepowcrfu! IooIs that have become available today for surface cbaracter-i28IiOII of ~ A _t ~ on characterization of solidsurfaces dCICrihe5 the curra.t status of theIe IechIIiqua along with

anum. 0( odICr poI8IOIe techniq- such as M<8bauer spectnB-

aIpy.

H7~~ty

The s.- of ftocali<Ml depends primarily Up<MI the selective by-drophobicity of the particles that arc to be floated. Except for a few,minerab are in aencral hydrophilic and hence amphipbilic surfKtanISwhich wiD sdcctivcly adsorb <XI the mineral 10 be IIoated are addedto !be systal1, Resultanl bydrOf'hobicity of the mineral depends uponsolution conditions such as pH, ionic streRltb, and tanperature. Someof the ccxumon tecbniqU5 thaI are used in ftocatioa r~b to deter-mine the nonwettability (or hydrop~ty) of the minerals are:

conlact angle nlC8SUraDCftts. iDduction time. bubble pickup. and mi.cro4\Olatioa experiments.

In 8dditiCMI to these, a vacuum ftocatiCMI i«:hnique developed by~huhmann and Prakash""" is also used for ~g incipient ftOIa-tiCMlCtXlditiCMla.

Contact anp mQSurana!ts aR carried <MIt on poIishcd surf-whaUI both bubble pickup aIId microftocatjon experiments can becarried CRU on cnashed ~a having the - size ranae as inthe 8CUIaI IocatDI. U~ 0.5 to 5 g of the mineral aampic aRused in ~ cella. die amount being dependalt upon thedesign of the ceiL Brief ~~~ of'tbeIe techniqua folk).,.

c.-ct A8IIe. Ta:bniq- to ~ contKt angle include di-r= - b8aed on IN'Ojected « p~ iaIaIc& aswell as i8direct evaluations in which the UIIic is cakuJaced frommeasured ~ or -ur.s - of ~Ie drops.'"

The ~ method intnJducal by Tagpn. Taylor. andI~ is quite popular among mineral processiDg ~. A sche-matic diapam aa modified by Ottcwill is shown in fiC. 93. bt thistechnique, the bubble formcd by the manipulation of a micromrAersyrinse is CCXllacted with tbe solid surface. aDd the angle is then~ from a photograph. Because of its ability to CCXltroI thevolume of' the bubble. this method has the advanta,e that one can-~ rececIiDI « advancing ana-.111 It can be used in a controlled~ aa was done by BaneI1 aDd CardwdPU or at hiP --~ aa carried <MIt by ~ aDd Taylor.-

In CCXltact anale measurements. surf- ~ to be polished andstored f~ fnxn pC8ibIe ~ts. Detailed discussions of' CCXltactangle ~IS have beeII publisbed.." ., Considerable hy$tere-lis oftaI exists in _red contact ana- due to surfKe roughness.contamination, noncquilibrium adsorp(ion eI'-. and mineralogicalheteroICR~ty .

The rajuimneIIt of polished surfaces f« contact &nile -ments often limits its practical imponance. as the mineral sampi5can neyer be used under such conditions for actual flotation tests.

I8d8edG8 TI-. It is galel'aby ~ that there is a definitetime period called the induction time betw~ tbe contact of thebubble with the panicle and its adhesion. Durin& the course of attach-ment of the bubble to the panicle. the liquid film separating thebubble aDd the solid has to thin and finally ruptW'e- The time laka!for this process of drainaae is believed to CCXltribute towards inductiontime.

A technique developed by S--Nilsson""" and later modified byEigeles- JOT involva vibratDI of' a captive bubble apinst a sub-n1erJed bed of mineral panicles. The frequency of vibration is variedand the time period c;oncspOIIdiDg to the frequency at which theattachment just (XCUf$ is taken as the induction period. Inductjooperiods have tICCn shown to vary from a fraction of a second toseveral hundreds of _ds. A CCXltact angle setup can be easilymodified to mas~ indUCtion time.

Babble Pick8f. In this technique a sinale bubble created at theend of a capillary by appiyiDg pressUR to a rubber squeeze bulb isCCXlcacted with a suspension of reagen~ panicles and the amountof minerals coIIa:ted on the bubble is .,.r;~ - A steady-stateconcentration of particles on the bubble surface can be obtained byintnJducinC shear f- into the syuan with the bdp of a paddlestina- .

In anochcr version cX this i«:hnique, the bubble produceci at theend of the capillary was CCXltacted with a mineral bed. rather thana sus1)ension of panicIa- See FiC- 94.

It is extremely important in these ta:baiques that conditions suchas the bubble siu. CCXltact time, positioDiDl the capillary tip withrespect to the stiner and the bottom of the aJOtainer. and stirringintensity be staDdardized. so that the information obtained from thesetests can be quantified.

MienftGt8dOL Microftotatioa tests using 0.5 to S g samples haveb«:ome very popular among ~ers in ~t years. A numberof cells have been ~ for microftocatioo tests, but onetbat has found wide application is the modified Hallimoad tube.'"

A typical Hallimond tube is shown in Fig. 95. The lower pan

MINERAL PROCESSING TEST PAOCEDURU 30.91

Intermediate ece n9AdvanaP.a. ,]. ~ dIIcr- m. - -II-

of die cell CCIaIi8II of a II- well with a frit bavinl a unifonn pore.. of .. '- tbu 40 JA an.acl-.t ~ the bcxtoaL The UtIfIer p8rtof the cell conIiIa of a bent .- tube with a vertical stem justabO¥C 1M bead. The top of the t1D is ~~ to a 8owmeceI' toIIIOIIitor the pi Gow. The preuure in the rcservoir (not sbowu inFic. 9S) -. be ";...1 to o.aaI tb8 .. low in the ~ ATc8on-CO8led IDaInctic stirrinl b8r pI8Ced inside die Ii- well isID8i to ~ in ~.CK-"'-:':~ The ID8peIic stirM' a8dsolenoid valva controiliac the 1M Sow can be activated by limenin S8cII a -y tbat a p)Od !'~ is obtaiDed ~ the bclinaiftlof the pi 8ow.

~y . la&elltizinl of the mineral is can;ect _t _aide tbeHallimond tube. This can be done by llimblini the mineral colIec:toc

BUBBLE PICK UP APPARATUS ,

IOIutioa « by Mininl the s,- usia, a malnctic atirrer or ~llinel' aIId BMIf« for a Ii- - 0( lime.

At !be c8d 0( thc co8dicionin.. !be pH 0( the solution is ~aIId !be ~ sol... is Ia--'a-..at to die fI~~lUbe widt mmimum nIftIuIeIIce. Frocbcn are Icnet'8ily not u..s intbilraniqIIe.

HydnJpI!oaic partida attach tbemlelva to lhe rilinl air bubblesand ~ to !be lop 0( !be ceil ne bled ~ falls into !bevenicaI - or stay anached to !be lop pan ollhe cell from where

it is asily ,.raIeIt.This letUp can be u..s for quantiwive expennlenU since the im-

pona8t hydnMiYJlamic variables sucII - the pa now rare. llimn,inteaatY. and ftowion lime can be coatroUed a.:.:utaleiy.

TOFLOW-

MET,ER ~~

~

.f.t"'It "

/30-

L__~:~-""

'--I

IIelll

IGROUNDJOINT-g-mm TUSING

CONCENTRA TE --

STEM I~TIRRING\_i IaAR-~ -L

-,PREPURIFIED

NITROGEN

CORK STOPPER-Q(NOT TO SCALE)

PIG.'" ~ .. . ~ --,.- F~". ~ H8Ii8.-d c.-."

3G-92 SAMPLING AND TESTING

be maintained usiq a pH-Scat. After eq~ the solid is Iepa-rated from the solutiCX1 pref~ly by ~trifuptioD aDder conatanttcmpet8tUR CCX1ditioaa and it is analyzed for the surfactant coa=ttra-tiCXI by stumrd anaIytieaI t«:hnjqua ~ as titratiOII or SpectropiJOotOmetry. The cbup in ~~ duriDI CCMlditiOlliDl is attributedto adIOI'ptjoII at the soIid/liquid interf- and kDowin& the IUrf-ata of the -pie, adsorptioo delllity is calculated. If 6- C is thecbanse in cc..-tratiOII of aurfactanc. V the orilinal voi- of soIv-tiaI. A the spa:ific surf- ata of the miIIeraJ (m2/1), aDd S theamount of solid in g. thea 6- C. VI (A.' S) will ~ the adsorpotQJ density. It shCMIId be _bered that in such caI~.~ thevolume of soIuti<M1 ~ by the solid is DeIIecfed. aDd if this is~ corra:IiCXIS will have to be made to the value of ~OIaDaa in .0- -pcioi-. deDsity a a functiCNI of soIid/Iiquid ratio WIdersaturatioa ccxaditioaa will be an indicat* of ~ eI"ec1S, evm thoupthis can also result f~ other ph~ eft"a:ts such as d(MJhIelayer inleractiOnl ~y at bish pulp density.

Adsorpcioo ClperimCDts can be carried out in vcsaeIs such as the~ tAown in Fas. 96-

Some of the pc.-ible artifacts durin, 8dsorpt* expeI'iments arelisted as follows:

I) P~"bIe adIOrptioa of surfactants on the container walls andthe related ~ a discuIaed earlier.

2) If the soIid/1iquid separation is carried out by filuanon. PCJISi"bleloa of surfactants due to 8dsorption on the filter paper or evm ~of soluble species such as calciIIm- f~ the paper.

3) Temperature chanse duriDlso1id/1iquid Iepar8IiOII. if ~trifu-Jationisused.

4) Prmpitatioa of surfactant counter ion compI-.-') Interf- durin, the analysis of a p&nicu1ar species by the

other spa:i~ in solUtion (e.s.. Ca- - has been known to .,.~ the

analysis of pIIc.phate in soIut* by atomic abIOI1'tion technique.-Similar problems may also arise when ion specific ~ are used).

Oftea. the ciIeaIical state of the adsorbed species is determinedby spa:troscopic tedmiques such as infrared. It should be noted tbatthe resulu of such tests do not provide a ~ti\'e proof for the forma-tion of identified COMplexes because of the P<MSibie chemical chansesm the state of adsoriIed species during the preparation and pl'e{re&t-ment of the sample for such spectroscopic analysis.

E1ectroki8etic~

~ 0( surfactanls on the mineral surface may be due toa number of iII~e f~ between the surfactant and the mina'al.In a number of systems electrostatic aMltribulions have beett ideutiftcdas important. - 8. Measurement of zeta poteutial of the panicle(potential at the shor plane) ~ dilrereut conditions can be hdpiulfoc- ducidatiIIg the role 0( dcc:trosIaIic contribulioas durinl ads0rp-tion. Two 0( the widely usaf techniqua foc- ~ zeta poteutial&R discussecI ill the following secti<ML

~ MobiJity. When a charged panicle mov~ ill and~ fidd, the dira:lion of movemcnt indicata the sign 0( thecharJe and the speed indicat~ the magnitude of the ~ ThispriJlcipie has beat usaf ill this te:hnique 10 ~ the zeta pocatial0( the panicle. Electrophoretic mobility 0( the panic1e is ~Ied tozeta potential by the equation:

v=.!!.:.4..."

w~ V is the vekx:ity ol the panicle. x is the applied add in v ICIa, " is the intrinsic mobility, , is the - pocential. and e is thediela:lric constant. Standard charts are available to read - potentialby knowiq the e*tropborecjc mobility.

SoIwions COQtaining about 0.1 % solids made ol 0.5 to S-" sizeparticles are taken in the eI«:tropboresis cell <- Fig. 97) and voltageis applied &CI'OII the two electrodes. Velocity ol the particls is daer-mined by observing the panicle movement under a microscope. Aver-ace speed ol I S to 20 panicles can be used to calculate the zetapotential of the sample.

AnodIer ~ ~ dcsip ~ -baliy of a modificd1,o,.mL Budmcr funnd with a S1em II8r&IIeI to the boC1om and witha bait lip at tile top of the ~ to diICbarae tbe froth.'" A microscopeIiide !'~ iDIide the ~ 8Cts . a bdIe. Unlike the Hallimoadtube, ia this ~ the raptizina of tile paniclcs can be dcMIC inthe ~ itlelf. AdditiCMI of a &ocher is Deca1atY here. The shape oftile ~ m8ka it ~_imt to define a pulp dawity whicll can be. much. 3 to S~ by wapt.'" In the HaIIimond tube, - tIIouIhthe M:hIal pulp den8ty is t»ly about 1~. the et"ective value is bi&bcr.as tile panicIcs ~ ~ only in tile lower p8ft. below tile MIldof tile tube.

The ps low SyItCIII and rat of the -bly can be similar tothOle dacn"bed earlier for the ~ tube.

In Idditic.a. a ~ devdoped by Tc.l\iD.x1 and F'-iDc- forkiDCCic Itudi8 and the Pur Cell- ~ by ~ ~ n0te-

worthy.~ Cell. Cbemica1 conditiODS for 8owion sepuaticm

of aIiDera18 can be established by aIicroftocatM)n experiment&. The~_t ICe, in a ~ design schaDe siICM&Id be ftowioo testsusit11200 to I(xx) I of material in iabor8Iory-size ~ Dalver.

W-. F&Ia'Jta. AIitair. and WedaJ ~ amool the mKhi-tbat ~ av~ for 18borat(Wy teItiDJ. They 8ft rep1ic:8s of cammer.Qa1 ~ ( ~ tbou&h tbete 8ft scaling distonions) and heDcethey may be ~ to tat the feaibility of a pnx:esa. ~ver: hydro-dYD8mic COIIdi(joas in ~ cells are a- to thmc of QltDmerciaJm8CbiDa than the microftotatioo cells. Also tile - of i8lIa" amountsof lamplcs can red- tile ~ anifacts -due to samPlins errors.

TYPcai COIIditiOllS for ftotatKMI experiments in . Denver ~ 8ft. ~ the Qid/liquid ratio is 20 to 30%; tile impeller speedfor CC*titiOlliDa is 1600 to 1100 rpII. for ~ 1400 to 1600f1X1', ud for cIeuiDIl200 to 1400 rpII; and the airtow is natura1.

The DIiDera1 is ~ with the =IIecfor lOIution for a prede-tcnained amouat of time. Other reagaIts such. pH DIodi6en. dcpIes-I8Dts, etc.. can be added duriq the COIIditiooing period. The orderof addition. _t added. dC., wiD depend uptMI the sYStem butsiICM&Id be Doted. Normally. _bat hillier _ts of rageat8ft required in tile Dalver ~ as compared to thOle in the aIicro/Ioca-ticm ceil T ~ tile end of alnditicx1ing. Crochet is added (MIBCor pine oil) and the sYStem is stirred for another 2 miD. Then theimpeller speed is reduced and aeration is begun. Flotation is altaidone until aJlDpiecion and it can be as m,b . I S min. Aoated productand tailinp 8ft anaIyW for.fade and =very.

In 8O(atQI tests for a procss desip, water from the supply that

is to be ~ aJlDmercially is pref~e.'"

For aptjmi~~tioa of ftot8IiOD alnditiCHlS, experiments should becarried out '-led UptM1 swistica1 design and the imponance of varia.bIcs abouId be evaluated acaInIiDcly.-

~

As mentioned earlier. hydn)pbobicity required for ftowioo is im-p8rtaI to the DIiDera1 by mans of amplliP8thic fealeDts which seIec.tively adIOti) «XI the miaeraJ. Tberef~ it is helpful to iavatiptethe ~ chancteristics of sucII 1alCDrs. known . co1\ccton

ormodilcn,«XIbochthemiaeraJtobeftoaredaswelJasthepngueminerals. TYPcai procedure frx adsorption experiments is as follows:A known wapt of the mineral sample (of known surface area) is

equib"br8teci with triple discilIed water «< ill iDdiI"er=t electrolytesoIutjC)llS which 8ft DOnIIaUy added to keep ioaic StreDIth constant).Wbcn the alnductivity and pH of supenlataDt solutions attain COD-S18IIt values (depeDdinc upon the systemS. the criterion of equilibriummay be dit'er=t). tile SyItCIII can be assumed to have attained equilib-rium. Daired volume of surfactant lOIuticm of known ~tratioois added to the SyItCIII at this ~ and COIIditjOIIed with the mineralfor . pncieICnIIiDed amount of time. It shCMI\d be pointed out herethat the equilibration time fm . mineral collector system can vary

considerably depending Up<M1 solution conditions such . pH.'" andhaIce it is Decesaary to determille equilibration time under dit'erentCOIIditions ill the relevant rance.

For casa where pH is a critical parameter conslant pH should

MINERAL PROCESSING TEST PAOCEDURES »-93

Stirrer ~

MO1Q'speedcattroI -:l-.

Acid lbo..di.spenMf AutomCItic

burette

~~~:opH"ectra~

~pH

Mete,

~cell

~C~trol

unitConstant

tempeNltIW'water

circul~

Testpulp

//"'.Water ...

Clrculaticn stirrer

~,., ~~of....,c-. ~ Nt

~ f7. ~ -.- ~ - ~~

w~ Cis.. pocaeal. " is ~cy ill \XMIe. P is pr-..n di8'er..-ICns the bed in dynes/cmJ, E is streamiq poteIItia! ill e.s.u.. e isdielectric -to A is spa:iic conductivicy in e.s.u.. C it cell COG-IWH. 8M R is raiswIce.

For ~ of ~ pcIteIIti8I - iII~ --a cell simii8l' ill pr;llClpie to (be ... da:rib8f by F--- witheither pIatiIIum or silver/silver chloride electrodes. Such cells caRROt.~, be safely employed to cc.-d- 5tIIdi8 as a fIIIIdiOII of --~ « 8IiIII ~ -- they have -, 81- ¥18JIS. A ra:cadydevekJpai- - ~ cell ~ be ~ to -1tre8aIiIIIpoteIItia! as a ~ of ~tmjon of 18pat. pH. f8npentUA.aliDlli-. etc.. with load pnciaiOIL A bri&l d8criptioll of this cell~

Tbe ccI1 ~ of two s-ns: die cell --*'Y - die dKtnIde~y . A KhetDatic diap8ID of die cell is Ii- in Pi.. 98. ThefonIIa' CC8iIa of two SOO cm' pyla &I- bulbs joi...t to e8Ch- of a ~ -pie tube of 1.3.- iIIMr diam &lid 9-cmieDIdL The ~ ~ of a -- cell. made for - w.CMIJy 6mitcd - of aIiaenJ an a¥aiJ8ble. - .. iMIde diameterof 0.8 cm &lid a lenltil of 7 Cat. The IMI1t. are provided with No.23 0 riq ~.ts which provide a - for the dKtnIde ~bly.

The d8:tzode ~ ~ of two P8fOI'8fed pI8ti.um disksof abou& 2.0 Cat diam &lid 0.2$ ca dIiI:k-. TIler ... wddaI OD~ side to a platinum puze (80 msh) &lid ~ die otiIa" side uWlyto a Ikm long thin plalinum rtMi of 0.23 cm diam. The decuodeIeD&tb is funtw ~ to J 3 cm by weIdiIII a thin tUDpten rtMiof 0.3 ca ~ OD to 1M pIaa.um rod. Tbe electrode IS r.-I to a2.0 cm ~ and IJ-cm I0Il1 ..- tube with two circular JroOYes

Si8Ce iDdiYidaaJ ~ an oIMer-s under the mtCn*XIpe. IIIistechnique Qft provide 8ft idea 0( the distribution 0( char.-. This isulef\JlliIICe in mineral miAtuns both pmiUvely and neprively clIarJedpeItic:I8 will be preIent.

U~ 0( hip voItqe ~ Jichl CODu--ty for a !oat period shooaIdbe avoid.a . this -y pnJd- cKcSIiYe '-in. 0( the -pieLHip voltap -y aIIO I8d 10 eIecuoIysis 0( water.

CAJaI-a.I ~ dI8I an av8il8llle f~ _IS 0(.-u~. -*iIy an the Riddk:k - - (Zaa Meta" Iac.),

taler - - (Paa K.- C4.), .-uiJPIM: ad - b8IISIMIft

analysis (Mi ~). - r-. (K:...Jj~), and raak%cia -- (Raak ~. EaIiaad).

The Mca-;JP8c;.-- aIt.1iIY IcIIniquc - be us8d OIIIy f~ 8MP8nid8. 0. the odI8' b88d. 8cIC8I-. is of'- carri.t - 'MiDI tiYdy -- P8nid8. Tbaaon. il IDaY be ~ 10 -

!be swf- gbarp 0( similarly Ii%8i partIcI8 for alndalioft with~ PanicuIarly in :Iller ~ SJSI-. dIarIC IDaY be depea-~ 1M P8Itide size ~ 0( 1M iatcrp8nidc ~ ad Iibcn-tioa ~ AJIo ia maay i--. size ~ ~ canlad 10 _W!'~-!!~ 0( !be sylCetn. 2U Thcnf'0Ie. -~I

0( %cia ~ - ~ partic18 can be U8IfIIl This can be -.-pIiaW by IIIiDI a i8j pcx.IaaI techDiquc.

~ --. P...w. In dIiI tecII8MI-. sofutx. is ~1hn1Up a piUI 0( miIIeraJ P8rtic:- and the pclletltiaI dc-.Ioped Xn8the plUio ~ as sllamia. potential. is ~ 51_in. poten-tial is tdatcd 10 %cia poIeDtiai by lbe equaIioII:

C - 4rlEIPXEIPXl/-IA - CIR

30-84 SAMPUNG AND TESTING

TOATMOSPHERE

F~'" A ;c 0( tk -,.-ioI coB - tk ,...aow

F1GCC8I8.-

The imporwIce of the IUtf8ce cbarae in determiDiDI the 8daorpotion propenia of solids bas beeII diIC\ISIed artier. The sutfxe ciw'sealso can ~use aurepIioa of ~ in mixed miJI«81 systems ifthepanjdcsuc~tdycballcdandnminsinglemiJl«81Syst-if the surface cbarae is rd8Iively low (say <20 m V).UI On the otherhand. similarly cbarJed mincn.Is can be dispersed well if tbe paniclarqIe1 each ocher. This piIeIIomeDOII is imponant for a number ofproce8Ie8 such as ftowion. ftocc:uiabon. selec!ive ftocculatiCM1, dewa.terinIo and filtrabon. Usd"ul infonnation !XI the dispeniOII/ftoceuJa.tiCXI propcnja of sIISpenIiODI can be ~ by -riAl KUJinCrate or turbidity ch8nse of suspensions. The foU-m, is a simplemetbOO for the nla8Ut-.t of the settlinc rate.

In this method. the lilht ~iued throuJh the suspcnsion ismeasured u a fuIICtiOII of time. The initial rate of <:baDce of theinleasitY of transmittcd IiIht is takm as a masure of the stabilityof the suspeasion. FICo 99 shows the eaenIia1 fcatura of the appal'&tus.It ~ mainly of a lipt soorce !XI one side of the chamber anda piIotoceIl !XI the other side to respond to tbe light transmittedtbrooch the serdin, tube. The pb~ocdI is ~~ to a recorderthr<M1lh a control. The whole system is maintained at constant tem-perature by passing tbennostaucaUy controlled Water through thechamber sUn'OUJIdin, the settling lUbe.

<M! it to bold two 0 riap. This tube IIoog with the electrode canbe itltnIdaccd iDto .-her sIus tube and be held inside this withthe bdp of the two 0 nap. The sIus tube is PI'O¥ided at ODe endwith . suitable 0 riJI& joint for COIttIectin, it to the cell -baydCICribaI artier. This arraDIeIDeIIt -- f~ movcmcut 0( eIa:.uodes iDside the cell eva1 after ~I the OUtel" tube in its pOIitioawithout any disturt.uce 0( the preISUR iDside the System and without~ any torque at the eIa:trode-liaSI ~ wbile pIepanDgthe millet'&! pillS-

The mode oC PI low and the eIeI:trica1 system arc describedeiIew~ -.. p_tiaI developed duriD& SU'eamiq is fcd into .hiP impedence (-1 0'" ~) ~cter which in turn is connectedto . reIXJrder. Tbe complete SyIIem can be autOmateli so that it canbe opentcd for boun ancI eva1 days.

p~ that should be takeII during suamia, poccntial ala-_is arc si- as foI~

I) Tbe platinum cIecuode should be stored in 10-' HHo.. Therat poccnbal oCthe~ should be less than 1 MY and whalCYerit ~ this value, the electrode should be cIaDed using aqua reIia.

2) The niuoaen pressure in the cell should not exceecf 20 cmHI bead.

3) There should be no precipiwion of pses in the plttg.4) There should be GO gap between the electrode and the mineral

bed.

MINERAL PROCESSING TEST PROCEDURES 3O-e5

THERMOMETER

:: -;. -_'I

-ca.sTANTTEMPERATURE

JACKETSILVER

BL..:J< FINISH -- -- -

- -- --- -

-

--

r CIAOJLATING WATER TO MAINTAIN

CONS T - TEMP.

LIGHTSOURCE 7

1- -- -- --

1- ---i- -

RECORDER- -SETTLINGCHAM8ER

SUSPENSION'~ER STUDY

~~~=- - - --

.- - - -?:: -.- -- ':, =~- ---.- - -- - - --. - - .---

- - -. -. -- -- --=- -= .-~ -- :. --- --- - -:,.--=-= -:"".-::--:- - -- -. -. --. -- -

------ -

-- -- ---- - -1 _-

\.':-~.~-:' - --

r:-~. ~I--~ : --- -

-

- -- -

j::- ::(--::-;;;-': -

- -- -- --- --

--

- -

--

-

WATER -25.CPIG. W. LiIM --- --., roo _.~ -

(II the WIlbdm, p1.re lecII-~~. the puB ~ the --- wIleD IIis jUIt 10IIcIIift,1he lOIut1on is .-red and is ~aced to !he surf~IenIiOtIai force IC:1inI ~ !he plate. 11111 C88 be daM 1CCUtateI, by.-. a ~ ( a ~ wo K8bII ~). Nor.maIIy pIaciIIum foil is .-s .. a _. Qt- maIeI'iaIIlbat QII be.-s an II-. TdCMI. wo - p8pcI' d8pcAdi-, upon the a¥8il8lality-!he-a,-.

A IChcmadc ~wx.. of a IIirf8I:e ~ ICIUp is sho.mill FIp. 100 - 101.- The ~ is aIOa8ted cm a - --riIIc 1M ~ r8iIiIII - ~ of 1M --- . ThelOlutioa w'- ~ Iensioa is to be ~ QII be IakaI ill ajIcteII8d cell (for -..t ~) -=k .. the ~ shoWII inFtc. 101.- The .-tput of Ik IIIicIob8I8Dce is felt illto the ,-axilol an ,I-y reconIer with !he ,I-uis for ri-.

TlIiI ICbIp C88 be .-s for equilihrium -.-15 .. wet\ ..dy-ec sun- IeIIIio8 Y8l-. T 0 ~ d, ic surface -a chill layer ollOlutiaa is remoYeI1 by Iuctioa which is applied gni-fanIIJ, fwo 30 sc. The ..n- --- recordiIII is beIun at lhe endol ~ whd dincd, ~ IIirf8I:e IeIIIio8 YS. bate plots.

~ lenIiCMI is ealmnel, scnsiciw 10 impuriliea and hence spe-cial care slKIUId he Iakca 10 a-.Jid all PC8ibIc conl8minants. Good~ ol the -- is ~ fIX" dimiIIatIq axtCKI anale et"ecuon the _red surf~ teosion value. Clanin, of the platinum~ ill _crated nicric Kid is r~o5i".o1ed ill addirion to the

Ia C8rrYiaI OUt a IeCtIiDI Gpcr;-c. rypM:8iIy a SOoCID" ~widI an 8~ pulp d8IIiry is shaken tborouply and ~ in theI8UIIDa chamb8l' with minimum pc-.jble delay. The ~ of the~ ia ~ _tin-'y rr-. the ~ft- ~I T1Ie seaIia& .-is e¥81uaf81 from the initiaJ slope of the inlensiry va. letdinl timecan-.

s-t.. T.--fnltb 8oC8aion iIIw/- duw in-'-= 1OIid/Uquid, liquid/gas.

a8d 1Oid/... Plopa18 of the 1iq8id/.. incerfacc - be. impJr-lant . tbar of the tOtid/1iquid inlerf-- - in datcmrininl lhe

8oC8aion ~~-- of aIiDCraIa. T~bajqa8 wue d8:ribed e8tticrfa ~ the sun-t ~ M the ~ illrerfacc.EAluiJibrium IUrfact8ftt IdIOrIMion at the liquid/air inlcrface can bei iadi~y by -naa the sa"- ~ of RrfacIaatIOIucx-. S- in .. 8CIUI 8IIC8Im cetI the life of - bubbi8 maybe ~ Ibott tJw they may aoc have IaclIed equilibrium with tbcsun-t soIUIioIL ~ in IddItM» fa equilibrium adIG.~it may be iIapCWt8at fa St1Mfy also the ~ of ~ at theliquid/airinrerfacc.-

A aUI8b« of 'lI:ba~~ ... a¥8ilabk fa ~ sutf~ ~of RrfacIaat a8lioaL The W"lu.eImy tII:baiqae delCnbed in the foI.Iowinl -=bon can be conveaiftdy II..t rOl' both dynamic . well- eq8i8briUIa surface ~ SbIdis.-

30-88 SAMPUNG AND TESTING

FIG. 1m. s..f8ce --

Microbol~ce

rquIar cle8DiD& (or orpaic contaminants by burning 0{ the sensorin a BunIaI flame. Even with all dIeIe precautioos, cenain systemssuch as the primary alkyl amine h~ calISe wetting pr0b-lems.