AO¥AN:ES 1M PtC)S'MATE flOTATlC*

8rlj ". "aud,11

Center for Research in "1nln, Ind "Inerll ResourcesOeplrt.ent of Miter111s Science Ind Englneerln,IMlyerslty of florio, GllnesY1lle, fl 32611

P. SO8Isunda,.an

HeII,.y ~ School 0' Mln.sColu.bla University. New Yort. IT 10027

"S~TFlotltton of phosphate rock around the world constitutes one of the .ajor

Ind _t effective .tneral processtn9 unit operltt~s. In J"lortdl, _tchproduces one-third of the world output, two stlte rewerse flotltton has been tnoperlt I~ since 1931. ,"t~ the depletion of blth grlde reserwes renewedItt.-pts have been ..48 to t8prove the efficiency of the current technology andto develop new athods to beneflcllte lower 9rade, c(J8plex phosphate ores. Inthis piper, I review of the efforts 114de to l8prove tile flotltlon efficiency Inthe exlstln9 pllnts Ind the new develOPGents rellted to processtn9 thephosphite ores with clrbonaceous (dolo.lte, calcite) 9aRgue are discussed.

IMPROV94ENTS IN 1tf[ FLOTATION (J" C(»IVENTlc-.Al 1)1[5

FlotAtl~ of phosphAte ores with pred08lnantly silicAte 9Angue hAS changedlittle over the 1ASt fifty yeArs. IkIrlng the past decAde, two considerAtionshAve AccelerAted the efforts to I~rove the efficiency of the conventionAlnotAtion process: dep1etlon of hlih grad. ores And chAnges In the product .Ixof fertilizers (LAwver, 19~). For ex~1e, the PzOs content of FloridAphosphAte Ntrlx hAS decreAsed f~ approxlutely 151 to less thAn 1M In tilelASt fifteen years. It Is expected to drop to About 71 In the South FloridA.Inlng district. At the s- tl_, due to hlgh~r trAnsportAtion costs,production of norul superphosphlte by direct IcldulAtlon of phosphAte rockwith sulfuric Acid hAS st~adlly decr~Ased In favor of high AnA1ySlS f~rtlllz~rssuch AS dl..-onAnlU8 phOSphAt~ (OAP 18-46-0), -onoA-.oniu. phosphAte (MAP 11-SO-a), _rch,nt Acid (a-54-a), ,nd trlpl~ super~sphAte (0-46-0). T1I~seproducts require high grAde rock (721 IPl or hl9her. llPl . 2.185 x 1 PzOs) to.Inl.lz~ processing and h,ndllng Proble8S. In addition to th~ 8Pl cont~nt ofthe phosphate rock, SOM of the other speclflutl~s d~slred for efficientprocessing Are the following:

426

427PHOSPHATE FLOTATION

I&A: The a~unt of Iron arid alUl8ln~ present Is an I~ortant considerAtionSTnCe It dete,..lnes the IIMIUnt of sludge produced In the wet-process phosphoricAcid plants. It Is required thAt the ratio of iron arid al..ln... content (ilsoknown IS 1M, O!" RZ03) to the pzOs content should be less than 0.095 (Rz03/PZOS

< .095).

CaO/PzOs Rltlo: The _unt of sulfuric acid l"equ1r_nt depends on theClo7pios !"at!;; In the U.S. I CaO/PlOs ratio of 1.6 is required.

"qO/PzOs Ratio; The amount of dolo.ltlc 11..stone 1~rlt1es, reported as "90content of the rock, vlr1es fr~ 0.05-0.7S"gO in the Apatite (lattice). SouthFlorida deposits will hive a MgO content higher thin lS. High _nts of MgO(> o.~) increases the viscosity of the phosphoric acid, thus rais1n9processing costs. Presence of excessive ~unts of Mg also Nkes it difficultto unuflcture I standard 18-46-0 (QAP) fertilizer product. Current fertilize!"production technology l"equlres the MgO/P20S ratio of the phosphate rock to be

less thin 0.015.

In Iddlt1on to the Above specifications, the SI/F ratio, the _nt ofor9anlc utte!". the chlorine arid cl~il8 content, and the reactivity of thephosphite rock al'e other fACtorS taken Into account In evAlUAting the rock for

use In wet-p!"ocess phospho!"1c Acid unufactur1ng.

A nulmer of the above 1..r1tles can be reduced by attrlt1onln9, scl'een1ngarid desl181ng operlt1ons. Furthe!" !"educt1on in the 18jlUrityleve1s is achieved

by flotation.

Advances In phosphate beneficiation operations which 1nvo1ve new1nstru.entat1on for washer design were discu~sed in a recent publication bylawve!" et al. (1980) Evllult1on of new conditioning equlp8el\t, flotation cel1sand reagent schemes have also continued ove!" the last decade and al'e discussed

belovo

ConditioninQ £Quip.ent

In the conventiOfla\ .thod of coa..se f..action (-16, +35 .sh) condltiOf1ing,the feed and ..eagents a..e .Ixed in a ..otating d cOfldltlone... Conditioningof fine phosphate (-35, +150 _sh) Invo\ves the use of a \ar-ge p..ope\\e...ixe... The th..ee 8Ost 18PO..tant facto..s which dete...lne the cOflditlone.. designare pu\p density, agitation intensity, and agitation tl_.

Pu\p density in both coa..se and fine phosphate conditiOfling Is ulntalned atapproxiNte1y 1M so\l.ds by weight. A new deve\Op8ent ill cOfltr-o\\ing the pulpdensity of feed to the colldltlone..s Is the use of a Lillatex Cyc\one whicha\\ows a constant pu\p density to be discharged even if the..e Is a va..latlon Inthe feed to the cyc\ones.

The pl"Oductloll of fines du..ing conditionillg, which can cause hlghe.. r-eagentcOfls~tlon alld \ead to nonselectivity, is especia\1y i8Portant when p..ocesslngsoft phOSphate ores. An a\temate conditioning device, ~ich essentia\lyinvo\ves ftowillg the ore ove.. . set of baff1es to cre.te the lIecessa..y.git.tlon, has been r-easOflab1y successfu1 ill conditi~ing the coar-se feed andill the .cld scf'Ubblng ope..atlolls to r"e.ove the f.tty .cld coatIng f..~ apatitepa..tlcles. This new devIce, known .s Ifg-Z.g, Box, Launde.. 0" Powe..1esscondftl_.., ..equl..es less powe...1Id has 1ess tendency to shon cf..cultr-eaQents. It h.s, howeve.., been obse..ved III plant eva1uation that the cu ent

ADVANCES IN MINERAL PROCESSING428

designs of these CO4Iditloners ,re not suitab1e for tre,ting ores fr- different1oc,tions. ~ve1op.ent,1 wort Is contInuing to optl.lze the design for,pp1Ic,tlons in conditionIng ,nd Kid scrubbing oper4tlons <Moudgi1 IIIdR,nsde11. 1985).

The optl... retention tiN In the condItioning t,nts v,ries fr- 2-5.Inutes. Pridgen Engtneerlng h,~ deve1oped , four t,nt conflgur,tion which411ows .ore precise control of the retention tl.. fr~ 2 to S.inutes.

Flotltton Cells

In the new f10tatlon p1ants, trends have been toward usIng 1arger ce11s.However, a new ce11 desl9" known as a F1oatalr ce11 has been undergoIngextensIve pl10t p1ant and In-plant eva1uatlon. It has been reponed thathlghe~ recove~y and g~ade are ObtaIned usIng the F1oatalr cel1 ~athe~ than theconventiona1 f1otatlon Nchines. low att~Ition In the ce11 Is expected to.Inl.lze fInes gene~atlon. Test resu1ts a1so indic4te that thIs ce11 is ableto f1oat coa~ser pa~ticles than the 1a~ge Mchanica11y agItated cel1s (lawveret 41., 1980).

~' ;

Reaqent Sche.es

fatty acids or their salts. because of thel,. aval1abillty and re1atlve1y lesscost are the 8Ist i..,o,.tant anionic su,.f~ctants tn the 88ine,.a1s Indust,.y(fue,.stenau and Ap1an. 1962; Sousunda,.an and Hanna. 1976. Leja. 1982).Anionic c01lecto"s t"Ployedlll ,.oughe,. phosphate flotation ct,.cults Inc1ude a_Ixture of crude ta11 oil. fatty acids and soap ski_lngs. Effo,.ts have beenundenlay to find a rep1acetlellt to,. fatty acids by synthetic reagellts to t..".ovethe reliability of collector efficiency. A nu~e,. of reagent sche.es such asesters of polycarboxylic acids, sulfosuccinic derivatives and su1fonatedderivatives have been developed (Wan9 and SIIith. 1978. 1980). Perfluoroalkylco.pounds associated wtth fatty acids have a1so been proposed fo" anionicflotation of phosphate o,.es (IIan9 et a1.. 1919).

Another recent developlaent 1s to ~Ioy only single stage notation Inphosphate beneficiation. for ex~1e. aP911catlon of amine ~lslfied in fueloil has been suggested as a reagent sche- to beneficiate phosphate ore in asingle stage flotation circuit. A alxtu,.e of a1kylamlne and ethera8ine. orusing a polyamine have been proposed as reagent sch_s for one stagebeneficiation of the- phosphate ore (Houot and Polgalre. 1980).

81alY et al. (198l) have developed a fa_Ily of ~hoteric type reagents suchas a1kyla.inoproptonlc. alkyla.inopropylamlnopropionic. and alcoyp,.opyla-lno-

propionic acids with the for-.1a:

R - (NH - CHz - CHl)n . 101+ - tIll - CHl - COO'

for f10tatlon of phosphate and sl1'ca us'ng the sa. reagent under different pHcond't'ons.

Recentl'1. to enhance phosphate recovery. ta11 0'1 collector additivesc_l'1 kno~ as "boosters. have been tested w'th 11.lted success. ThecQ8Poslt'on or the addit'yes 'S not g'yen by the .anufacturer.

429PHOSPHATE FLOTATION

In the c.tlon1c flot.t1on c1rcu1t gellt1n1zed st.rch MS been used toenh.nce select1Y1ty dur111g sl1lc. f10t.tlon. It Is bel1eYed tMt st.rch~Iecules .ct .s . pIIospll.te depress.nt thus 1~roylng the s111c. r1ot.tlon.It Is .1so suggested th.t starch m1ecu1es .dsorb onto the -act1ve- sites OCIc1.ys thus reducing the ~unt of c011ector required for efflc1ent s111c.f10tat10C1 (l.wver et .1., 1983). It h.s. however, been reported th.t p1anttrl.1s of st.rch with .11phAt1c ..1ne type co11ectors hAve not proven to becost effect1ye .t this tl_.

The .dyantAges of synthetic surf.ce ~1flers oyer natur.1 poly.er1cproducts such AS starch .re the e.se of structurA 1 chAnges to sui t A spec1 f1cAppliCAtion, .nd cons1stency of the product fr08 one bAtch to Another. ",g.r.jet .1. (1985) hAve discussed the .odlfler .ctlYlty of p01YAcry1..lde typepo1y_rs conta1n1ng both hydroxyl .nd carboxy1 funct1OC1.1 groups in c.tl0Cl1cf10tAt10C1 of sl 1 Ica fraa the phosph.te rock. These 1nvest1gators reported th.t20 9/T .dd1tlon of . ~Ifler (phospMte depress.nt) of . gener.1 c1l81c.1for-.1. g1yen be1ow, resu1ted In upgradln9 of . 5M 8Pt feed to 741 8Pt using500 g/T of. c_rc1.1 Mille .s the c01lector. WIthout the ftldlfier .concentrAte si.i1ar in grade w.s achieved but the aPt recovery was 8n .sopposed to 911 when the .1 fler WAS .dded to the suspension.

-( -tHt-tH- >X - (-tH2-tH- ),-I IC~ C.OI Iratt NIl

"'--OMICoc.!

Structure of Modifier

In the above 8Odifier. both hydroxy1 and carboxyl functlona1 gf"OUPS are onadjacent carbon at08S attached to tile a.ide nltf"ogen. In genera1. the presenceof (»1- and COO- In c10se proxl.ity appears to be iqlortant. Recent1y.synthetic depressants for phospllate during si1ica f10tatlon were IntroducedInto the urket. P1ant trla1s are underway to deten81ne the cost effectivenessof these additives.

All of tile above efforts have been directed towards I~rovlng tile notationefficiency of separating sl11ca gangue fro. apatite (francolite). A nullber ofpast studies and current investlgati'ons (Ru1e. Gruzensky and Stickney. 1970:Cklal. 1973: Oalilln and Fergus. 1978: Jollnston and leja. 1978: lawyer. Mclintockand Snow. 1978: ~four et a1.. 1980; LaWYer et a1.. 1982: L1ewe11yn et a1.,1982: Fu and So.asundaran. 1985; MO1Jdgll and Chanchanl, 19854. 1985b. 1985c:Ru1e and 0a1lenbach. 1985) have been related to beneficiation of phosphate orescontaining ca1clte or d0100aite as the I18P\Irlty. 1hese efforts have .ost1yInvo1ved deve10plng new reagents and 8Odlflcatlons of the conventionalprocessing sch-s to achieve the desired separation."

ADVANCES IN MINERAL PROCESSING430

A review of phosphite beneflciltion including the re8)vat of carbonate'~ur'ties fr- apatite h.s been pubtlshed by ~ot (1982). The Njordevetopowents in the are. of apatite (fr.ncolite). dotooalte/calc1te separationare discussed betow.

tqn!ous PIIosphate Ores

Pyroxenite type phosphate ores fro. PIIalaborwa consist of ~rbonatite coatedwith a serpentlne_gnetite-apatlte rock. ~atite Is reported to be unlfor81ydistributed and is .ixed with copper, titanlferous Ngnetlte. uranlu-. andthoriUt8 as accessory 8inerals. Magnetite Is removed by Ngnetic separation andis followed by copper flotation using potassiu. alRYl xanthate and triethoxl-but}ne. The reagent sche- for- apatite-carbonate separation invotves sodlU8si11cate as a gangue depressant. a dispersive agent (0.75 to 1.5 kg/ton). andtatl 011 (0.Z-0.Z5 kg/ton) as the cottector-. In addition, nonylphenyltetr-a-gtycot ether- is used as a depressant for carbonates and as a dispersant of talt011 cottector. The P20S content of the concentr-ate is 36'(t5-ZS' P20S feed)at a recovery of 75-86'. In cases where car-bonate content Is hi~er. largeramounts of nonytphenyttetragtycot ether along with potysaccharldes (0.1 to 0.15

kg/ton) ar-e needed to controt the froth voluR (lovelt. 1.976).

In 8r-azi11an apatites. depr-esslon of carbonates and iron oxides Is achievedat pH 10 using caustlclzed starch. Tall oit fatty acids are used as collectorsfor apatite (Silvia and AIIder-y, 197Z. 8etz. 1979).

FlOTA TIOIC fJ!' ~SPIIA TE atES vIm CARBONATE GAI«OUE

The two ~st i~ol"tant types of phosphate deposits fro. an ec_ic point of

view are the following:(i) Endogenic dePO'its: igneous alkaline c~lexes and carbonatites

(ii) Supergene deposIts: urIne sedi.entary deposits, phosphates, guano.

At present, urine sediMntary deposIts constitute approxiutely 801 andigneous deposits approxiutely In of the total world output of phosphate rock

(Houot, 1982).In the igneous (endogenic) deposits the phosphate .ineral is well

crystallized and exhibits a greater floatability than the phosphate .ineralconstitutIng the sedl_ntary (supergenic) deposits. Phosphatic ores frOl8Phalaborwa, Jacupiranga, S1ilinjarvi. and Jhaur Kotra are SOM of the igneous

ores which contain carbonate gangue.Flotation schemes to beneficiate igneous phosphate ores associated with

carbonate gangue have been developed. However, appl ication of these _thods toprocess sedi.entary phosphate ores have not been successful. This has beenattributed to the following factors:

(i) High specific surface area of sedi.entary ores;

(It.) Inability to liberate carbonaceous .aterial fr~ phosphates in theflotation size range;

(1ii) Substitution of CO~- and f" for PO~- and Kg!. for Cal. in theapatite lattice.

PHOSPHATEfLOTAnON 431

The unIque feAture or benefIcIAtIon or FInnish phosphAte ores, ~Ich contAin101 ApAtIte. ZZI cAlcIte And do1o.lte. 651 ph10goplte And 31 .-phlbole Andother sl11cAtes, is the use of "-substItuted SArcosIne. An ~lIoterlc c011ectorof the r011~1n, type:

CH,I. -R -. - C"a - coo1H

This reagent acts IS In anIonic collector for apatIte flotatIon under basIc pHcondItIons (pH 8-11). Klukkola (1980) his reported that after three c181nerf10tltions of the above ore the ~rlte ana1yzed 351 '20s and 1.61 MgO asCO8plred to the feed Which ,ontlfned 4.01 '20, and 14.11 KgO. Apltite recoverywith 32.5 9/t of the above collector It pH 9.6 was 851 (Hellsten and K1fft9bert.1918, Ktukk01a, 1980).

, "

$tdi_tAry PhosPMte Ores

PhySiCAl sepArAtIon ..thods su~ AS hlAY1 8edtA sepArAtton. JrAvttysepArAtton And Attrtttontn9 to reduce the MgO content of sedi_ntAry phosphAteores such AS fro. South F10rtdA Mve '-eft investIgAted tn the PAst (lA~er etAl.. 1980: Dufour et A1.. 1980; Mtn-.t PAtent. 1980; 8AU8&nn And Snow. 1980;Cox et 11.. 1980; Vlege1 And .An9. 1984). Alternlte techtltques to beIIefictlted01~tttc phosphAte ores Are bAsed on the dIfferences tn surfAce ch..icA1properttes of the two .Inerlls And tnvolve flotAtton of ApAttte ordol~tte/cA1ctte f... thetr .txture.

CAtIonic FlotAtton

Res.,rch.rs It InternAtIonAl MinerA1s And Che.icil Corp. hAve developed Aprocess to flOAt ApAtite f~ dol~lte fr~ conYelltt~l conc..trAte ustng IcoelnAtton of priury AliphAttC A.ines And kerosene (Sno~. 1979: lawver etAl.. 1983). The resu1ts tndtcAte thAt A product contAtntng 1ess than is MgOAnd I 8Pl recovery of .re thAn 901 CAn be obtAtned usIng the above process.Soto And IVISAkt (1985) hAve Attribvted the se1ecttvtty of the reAgent Sche8eto 10wer s01ubl1ity of the pine-phosphAte c~1ex for8ed on the ApAtitesurfAce AS C~Ared to the ..ine-cArbon&te c~lex fon8ed on do108tte.

Antonic F10tAtton

Processtng of U.S. PhosphAte Ores. f1ort" phosphAte depostts constitute AuJor plrt of the world reserves- of phosphAte. With the dep1etton of highgrAde reserves tn CentrAl F1orldA. re,IAce8eftt production ~t11 co.. fro. theSouthern extenston of the current .IIItll9 dtstrtct. The future phosphAtedeposits tn F10rtdA And Wtstern UIIlted StAtes contAIII higher POUnts ofdol08tttC It..stoll. t.rttles thAII the rock presellt1y betll9 processed.SeverA1 .tt.-pts Are underwAy to reduCi the cArbolllte content of the U.S.phosphAte rock. A brIef revl.. of these .fforts t$ presented be1ow.

IMC PROCESS: llwver et A1. (1984) eXA.tned fAtty Acids And their s~ps.Inc1udtag sodl.. 11ky1 su1fAtes And petr01- suTfonAtes for f10t.tion ofd01o.tte fro. Ap&ttte At pH 5.6-6.2 tll the presence of il1or,.nlc depreSsAllts

ADVANCES IN MINERAL PROCESSING432

such as phosphates and fluorides. These investIgators reported that sodiu8tripolyphosphate and hexa_taphosphate with a proprietory anionic coll.ctoryIelded the best results. The applicatIon of thIs process to n MgO phosphatefeed that was fIner than 300 - (48 _sh) yielded a concentrate contaIning lessthan II MgO at BPL recoveries in the range of 5O-9OJ.

U.S. BUREAU CE MINES PROCESS: Llewellyn and coworkers (1984) at the U.S.Bureau of MInes observed that addition of sodiu8 sil Icate depressed dolo.ltepartIcles. ThIs process yielded a concentrate contaInIng 0.4 to 1.361 MgO withPzOs recoverIes In the range of 72 to 961. The InvestIgators rec_ndedfurther oval of dol08lte by $Oz leachIng.

Continuous flotatIon test results after two cleaner stages, using the U.S.Bureau of MInes process, are s_rized In Table 1.

In another study at the U.S. Bureau of MInes. Rule et al. (1985) developed atechnIque to selectively float carbonaceous illP\lrltles. Fluosllicic acid wase..,loyed to depress phosphate and an aqueous fatty acid ...lslon was used astile collector for carbonate uterl.ls under slIghtly acidIc pH conditIons.Pilot plant flot.tlon test results of an Idaho phosphate ore are presented InT.ble 2.

Table.1. U.S. Bureau of Mines Flotation Process

Fatty Acfd - Fuel Ofl (2:3) .1 kg/tNiGH, NaaCOJ . 0.3 kg/t (each)

Sodfl8 Sfllcate .0.5 kg/tFrother .0.01 kg/t

Assay, S

P2Gs CaG MgO IllsotO1strtbutton. ,P20s "gOFracttOfl

9.60

31.30

16.60

41.10

1.80

0.55

59.803.40

100.00n.1O.

100.00

6.90FeedConcentrate

* Tota1 recovery (f1otatlon feed recovery 89.~).

TYA PAOCESSES: Hseih and lehr (1985) used diphosphonic acid to depressphosphate whl1e f1oating dol~ite with o1eic acid. These investigatorsindicated that higher MgO content in the f1otation feed NY require higherfatty acid dosage. They a1so rec_nded desll.ln9 the 20 .. (625 _sh) toreduce the reagent consuaptlon. 8ench sca1e f1otatlon results of an Idahophosphate rock presented In Table 3. indicate that the reagent scheme developedby these Investigators is effective in separating dol~ite from apatite.

433PHOSPHATE fLOTATION

rib1. Z. F10titf~ of 1ft Idiho Phospliite h

FittYiCfd .0.70 tg/tHzSfF, .0.45 tg/t

Prfury .therA8fne ic.tite . 0.20 tg/t

Ass~.YS SPIGS "90 StOa

O1st,.tbutt~ S

PzOS "gOF...ctIOll

Feed

Concentrate

ZO.8

n.s1.100.84

zo.s19.4

10089.5

10055.8

In another proc.ss deye1oped by lYA (Anon.. 1983). HzSG- ts a6ded to st11CArree rougher concentrate to benertctate ca1careous phosphate ores. Se1ecttyenotation or carbonates fr~ phosphite Is attributed to dtrferentta1 desorpttonor the ratty acid co11ector on the phosphate 8lnera1. No conc1us1ve data.however. Is presented regarding the ~nlS8 or se1ectl.. notation.

MINKET PROCESS: This process (Mln..t Reche~che. 1980; Dufour et a1.. 1980)a1so 1ny01yes a carbonate notation sta~ using an anionic c011ector Arterconyent1ona1 doub1e stage notation. The phosphate concentrate was conditionedwith the col1ector ~ a phosphate depressant at pH 5.5. The reagents used inthese tests have not been 1dentlrled. The rlna1 p~oduct assayed was 1ess t~nII MgO with 8Pl ~ecoYe~les or 48-851. In this case also. the 1nYestlgato~sr.,o~ted hlghe~ ~ecoYe~les ror pa~tlcles flne~ than 32 _sh.

r.b1e 3. Bench Sc.1e F10t.tton of -za .es- +20 .. Phosphate Rock fro. Id.ho

Isoste.rtc AcId (001o.tte Col1ector) .0.5 kiltHydroxyethyll dene DlphosphoRlc Acl G . 0.5 tg/t

(60S .cttwe phosph.te dep~s."t)Dodecy1..t"e ~droch1ortde . 0.2 kilt

(StllcI C011ector)Colldl t1O1\t"1 pM . 6.4 (Oolo.tte Flot.t ton)

1.4 ($t11cI Flotlt1O1\)

AsSIY. ,

'2Gs C.O MgO St02

Distrtbvtt-. ,PzOS "gOFr.ct1on

FeedConcentr.te

25.60

32.00

39.2046.50

100.00

82.70

100.00

3Z.00

1.90

0.90

16.20

8.00

ei

- -.ADVANCES IN MINERAL PROCESSING434

~

M STAGE C~DITI~I~ PRcr.ESS: It his recent1y been reported ~tseparation of do1.lte fro. South F10rida phosphate can be achieved by firstconditIoning at pH 10 with fatty acId followed by recondltlontng at a pH be1ow4.5 (Moudgl 1 and Chanchanl. 1985.. 1985b. 1985c). The recondltlonlRg pH aftdcollector concentration were found to be ..jor par.-eters In flotatIonselectivity. The ..chanls. or observed selectivity Is .ttrlbuted to hlgh.radsorptIon on do1oelt. at pH 10 as CMPared to that on apatite and trans-forwtlon of oleate species to 01elc acid .lecules upon reconditioning. Benchscale test results of the two st.,. ca.dltlonlng proc.ss are proalslng. It IsIndlc.ted that the rea,.nt concentration .nd the agitatIon Inttftslty durIng theconditionIng procels have a ..jor Influence on the flotation selectivIty.

I. . process developed by Fu .nd So8asundaran (1985) .1lrarln red S his been.-ployed to achleye an effective separation of ap.tlt. ~ ~lclte .sln9 01..t.as the collector. They fOllnd th.t alizarin red S adsorbed .re on ap.tlte th.non c.lclte and consequently acted as an apatite depressant. l1Ie best rflu1tsto date ..r. obtained by conditioning the .In.ra1s for one .Inute In a1lzarl.red S solutions between 2 x 10-' and 5 x 10-' k801/.s .nd flo.tlnt with oleateat pH 10.5. For a 50:50 .Ixture of a,.tlte and ~lclt.. theS8 Inyestl,.torsr.ported 90S flotatton or calcite al co.,.r.d to 1M for apatite. Tests are Inprogress to underlt.nd the _chanls. of flotatton selectivity and to optt.treth. process p.r_t.rs.

l1Iese investigators ~v. also rtpOrted that conditioning tl.. his a ..jorInfluence on selectivity possibly due to dlfr.r.nce In the ktn.tlCI of r.agentadlorptlon on the two .lnerals. In addition. .dsorptlon of th8 dlss01ved.lneral Sp.Clfl can also a1t.r the surface che.lc.1 behavior of the soltdsubstrates. A detailed analysts of the rol. of dtlsolved .1ft8ra1 species 1ftelectrokinetic and flotation of .patlt. and calcite has recently been presented(Ananth.paa.nabhan and So8lSundaran. 1984, A.ankO",h .t a1.. 1985).

Proces~tng of PtIolpll.te o..-s ~tstH the U.S. A ~r of ledl-.ntaryphosp~ate deposIts OIItstH th8 U.S. also are Issociated with carbonategangue. Several atte~ts ~ve been reported tn the Itter.ture to separate thecalcite and dol08tte t.purtttes froa the phosphates. A brier discussIon of thefindings by various rese.rchers ts presented below.

TASIT (nJRKEY) PHOSPHATES: Fatty acid flotation of carbonate g.ngue fro.Tastt (Turkey) phosphate ores using a phosphate depreslant wal atte..,ted byAtal.y and c_rk.rs (1985), 11tes. Inveltlgators evaluated fl_ostllclc Kid.dlphosphonlc acid. pIIoSphorlc Acid and an al_l- lu1 fAte-tArtrAte c08P1ex alth. deprtslants. 111. 1.It two deprusants separAtely or In cO8bI"atlon wreround to be succes'ful to a It.lted extent. For example. flotation of a 10.41PzOs pho,phAte ore at pH 6.5 using 17 kg/t pho,phorlc acid, 250 ,It Alz(S~)],SOO g/t tartrAte and 5 k9/t oleic Kid yielded a product cont.lnin9 26.351 PrOs.t a PzOs recovery or 57.851.

KARA TAU (USSR) PttOSPHATE5: Ratob,11kAya et AI. (1975) hAve described Aprocess for flotAtion or an ot'e CO8Posed of phosph.te. cAlcite. dol~lte AfIdquartr. 111.., achl.yed the depression of pholp~tel ultn9 Ot'tho9bolPhortc KIdand a ratty Actd collectot' tor f10tatton of carbonates. After rl0.ttn9carbonates. tall 01,. kerOlene and sodlu. slllc.te are eq>loyed to float outphosphate at pit 7.6 - 8. Flotation resultl or ~rA Tau ore uSI"9 thll reAgentsc~ are pt'esented tn Table 4.

M~OCCAN PHOSPHATE ~E: SePAt'Atlon of cAlcite rro. A Moroccan pholphAte orewas obtained using O.g kg/ton of fatty acid And a few hundred gra8S of a 2:1

PHOSPHATE FLOTATION 435

Table 4. flotation or Ka,.a Tau Phosphate OI"e

Synthetic fatty Acid. 0.3 tg/tPhospho,.tc Acid.' tg/t (pH 51

Soda . 1.7 tg/tKer-osene . 0.5 tg/t

Sodi- SI1icate .0.5 tg/t

AssaySPzGs MgO l"s01

Olstrlbutlon. I'20S "gOKaterlal

22.5

28.0

3.01.3

20.0

11.0

10075.0

10026.3

Feed

Concentrate

.ixture of all8inum sulfate and tartaric acid as tile pilOspilate depressant(S8ani et al.. 1975; lIouot and Polgalre. 1980). Flotati~ results utilizingtile above process are presented in Table 5.

MUSSOQ(IE (INDIA) PHOSPHATE ORE: To beneficiate ""ssoorie pllospllate oreswitll high carbonate content. Rao and co.orkers (1985) .-ployed KzHP~ asph01phate depressant. Flotation of calcareous i-.>urltle1 with 1 k9/t of oleicacid at pH 6.5 in the pre1ence of 3 kg/t of KzHPo- depreS1ant yielded aconcentrate analyzing 27.6' P2Ds at a phosphate recovery of about 601.

SWEDISH IRON/PHOSPHATE (ME PROCESSING: The ~ktu1vaara iron ore in Swedencontains heNtite. apatite. ca1cite and 8Ignetite. The phosphoru1 content ofthe1e ores varie1 frOal 1.5 to 5'. 801in (1983) ~Ioyed water glass (28.91SiD2. 8.991 "a2D) to depress calcite willIe floatln9 apatite u1ing an ~holytlcfatty acid derivative a1 the co11ector at pH 6. He also exaMined tileeffectivene1s of other addltive1 1uch a1 HzSiF6 and NaF2 In achieving thedesired separation. The selectivity achieved is attributed to the differencein 101ubl1ity betveen calcite and apatite to control the fatty acid adsorptionon tllese .inera1s.

Table 5. Flotation of Phosphate VlthDoI08ltic Gangue

D1eic Acid. 1300 - 1500 9/tAluMinum Sulfate. 200 - 250 g/t

Na-K-Tartarate .400 - 500 g/tDenatured Alcohol. 650 - 750 g/t

Soda (pH 7.8) . 5DO - 600 9/t

Distribution, ,

pzOs KgOAssay, ,

PIGs "90 SIOzFr4ctton

FeedConcentrate

23.24

32.14

3.29

0.43

9.69

3.77

100.00

83.94

100.007.93

".

436 ADVANCES IN MINERAL PROC~SING

SYR1AR PHOSPHATE ORE: Clertcl et al. (1984) haye reported beneficiation ofa sedt..ntary phosphate rock fro. a Syrian deposit associated with acalc.reous-slllceovs flfttUe. ~81l8Ployed the f011ow1nt three differentrlagent sch_s to ach1eye the desired s.,.ratlon:

(I) Flotation of the c.rbon.te ~n9Ue .t pH 6.5 us1n, -.u1s1f1ed f.ttyacid (2.1 kilt) .nd HISIF, (ZOO g/t). followed by se11ct1yefloccul.tlon of silica w f10t.tlon of phosph.te using ~lt1on.1fatty acid.

(II) s.1ectlye flot.tlon of the c.rbon.tIS .t pM 11 w s111c. at pM 4 1.two st89s using sod1.. sa1t of y..1ky1-..1no-proplon1c acid (an..photertc co11ector). The.-ouftt of co11ector added in the twof10tat Ion steps was 1050 g/t for c.rbon.te .nd 700 "t for st I tcaflotation.

(111) F10tat1on of carbon.te with the reagent In (11) .boye f011owed byselect1ye floccu1.t1on and flot.tlon of the phosph.te with excessfatty .c1d. Carbonate flot.tlon WlS conducted .t pH 4 with 700 "tof the collector. select1ye f1occu1at1on .nd flotation of phosph.tewas acc~1tshed .t pM 6.5 using 1440 g/t of t.II otl In two st.ges.

A co.parlson of the phosph.te concentrates obt.1ned by the .boye ..thods Ispresented In Table 6.

OTHER SEO1"ENTARY ~E: In a processlllg sc~ deye10ped .t IRQ!. Fr.nce.d01o.Itic phosph.te ore ~s been beneflcl.ted using phosphoric esten .sc.rbonate collectors. .-d ..Ine .cetate as a co11ector for phosph.te (I.udet.1983). Under optt.u. cond1ttons a phos~te ore fro. .n undisclosed loc.tlonass.y1n9 26.31 PlOt. 3.71 MiO w.s concentr.ted to 341 PIGs ~ 0.241 MgO at.PIOS recoyery of 89.M. Another slall.r "~Ie cont.ln1ng 2).11 PIGs. 4.751"gO w.s beneficiated to .ss.y )3.11 PlOt and 0.731 MgO at a PIGs recoyery of69.11. It w.s deteralned In this study t~t I~ pulp density duringcondltlonln9 .nd short condtt1onlng tt.. required less collector.

Houot W coworten (1985) ~Y8 ey.1uated beneficiation of phosph.t1c oresassocIated with. siliceous and lor . c.rbonatl g.ngue using .8pIIoterlc _1nederlyatlyes as flot.t1on c011ecton. 8.sed Oft the flotatIon of ores f~ ~l~.Djerda. Tunisia; Sra E1 ~ertane. TvtlISII; MIu T.rtur. Egypt; Sidl ~oul.Morocco; Ind ~rdel County. Flor1dl. U.S.A.. the .boye reselrchen concludedthlt f1otlt1on results with MPhoterlc cor lectors were .t lelst as good IS byusln9 other re.gent sChe..s developed for the respective ores.

TAble 6. flotAtion of SyriAn PIIosphAte Ore

feed . 2~.61 '205. 49.11 CAO. 10.41 CO2 And 6.51 SI02

}

~

()

437PHOSPHATE FLOTATION

Concluding R_rk~Beneffcfatfon of igneous phosph.te ores with carbonaceous g.ngue f$ not a

Major problea. ~ the other hand. separation of carbonates fro. SedfRntaryphosphates cannot easfly be accO8(>lfshed due to their c~lex structure andpresence of different a~rphO4ls and porous phosphates In these deposits.

A nullber of potential reagent sche.s and flotation process ~f ffcatfonshave been proposed in the past. but their econo.lc feaslbl' fty at c~rcfalsca'e has not yet been established. The various flotation atte8pts can becategorized as those fn which phosphate Is floated out of carbonate gangueusing a catfontc col'ector. l1Iese att~ts are ,t.tted tn appltuttoll becausea Njor c.onent of the ore (-901) ts floated out 'e.vlllg the t.purtties fnthe stnk. In the second categor,.. reverse flotation Is atte..ted. carbonates

being recovered In the froth .nd the sink fraction constituting the phosphate

concentrate. l1Iese efforts un be assigned to - of the following: (f)flot.tfon of carbon.tes with a f.tty acid collector fn the presence of a

phosph.tedepress.nt; (ff) develop.entof c.rbonate selective reagentsch..s. The key to se'ecttvtty fn the first c.se fs the effecttveness of thedepressant. In this regard. n..r of depress.nts have been ex..ined -phospllortc .ctd. dfphosphonic actd. su'furtc .ctd. fluosillcic acid. alulIl.-J8sulfate-t.trate co.plex. altzartn red S. and sod. glass. SOlIe of tile carbonateselective reagent sth..s e8ployed tnc'ude. pllosphatlc esters. Na salt of n-alkyl-a.fno propionic actd - and "-substituted sarcosine. tile last two betnga,.lIoterfc tn nature.

In another process known as two-stage conditioning process tile dolo.fticphosphate ore ts reagentlzed first at pH 1O with fatty acids followed byrecondftfontng of the pulp at . pH aroand 4. pH 8Odfflcatfon un be achtevedby HHOJ or H250,. Flotatfon at pH 4 leads to recovery of dol-fte in the frotllleavtng apatite (franco'lte) fn the sfllk. Bench scale evaluation of thisprocess is underway and looks pr~fsfng.

It ts clear fro. the above discussion that SOlIe of tile f'otatfon sthet1e5have a potential to be successful. however. the dffferencesfn the nature ofthe ores to be Pf'ocessedw1'1 requfre optt8tzatlon of the major par..ters forores fr~ different locations. It is essential that the basic _chanfs8S ofthe process be co..,letely understood fn order to find a .ore gener.l solutfollto the critical probl.. of beneffatfon of low grade co..,lex phospllate ores

assocf.ted with urbonaceous gangue.

Acknowledge_nts

The authors acknowledge Flortda Institute of PIIosphate Research (Contract182-02-023 (81114) and 1 83-Q2-037R (P$» for part1al ftnanctal support of th1swork. One of the authors (8*) thanks the NSF-PYI award prograta (CPE 18352125)for addtttonal financial support. Any opinions. findings and conclustons orrecOnlendattons expressed tn this publtcation are those of the authors and donot necessar1ly reflect the views of the Florida Institute of PhosphateResearch.

~ , ~ ...

~

,

ADVANCES IN MINERAL PROCE~tNG438

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440 ADVANCES IN MINERAL PROCESSING

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PHOSPHATE FLOTATION

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