FLOTA'l',rON OF LOW GRADE MUSSORIE PHOSPHATE ()~

D. Vaman Rao*, H.K. Narayanan*, u.s. l~yak*and

K. Anan~~apadmanabhan** and P. Somasundaran**

ABSTPACTSeparation of Mussorie rock Phosphate (P20~ - 20') from ~ttar PradeSh,

India, cortaining pyrite, calcite and other carbonace°u.s iD()urities by flo-tation has been successfully attAmpted to upgrade the phosPhate values.I. sed on Balltmond cell flotation results of single and synthetic mine~almixtures of calcite and apatite usin~ oleic acid and potassium phosphate,conditions were obtained for the separation .,f calcite from apatite whiC'.hia considered to be the most dif.ficUlt step in the beneficiation of calcar-eous Phosphates. Further studies using 250 gms of the mineral (-60 +150and -150 meSh f~actions, des limed) in laboratory size Fagergrpn sUbaerationmachine employed a stagewise flotation viz. carbonaceous materials usingterpineol, pyrite using pc:~ssi ethyl xanthate and calcite using oleicacid respectively. Separation was, h~ever, found to be unsatisfactory inthe absence of a depressant.

Among starCh, hydrof~uosilicic acid and dipotassium hydrogen phos-phate, which we.ce tried as depressants for apatite in the fi.nal flotation8tage, dipotassium hydrogen phosphate proved to be superior to others.However, t-.he tests with the above fractions did not yield the required grade.'!his was possibly due to insufficient liberation of the phosIilate mineralfrom the ore body and dlfferent experiDental conditions due to scale \fPoperations. E]q)eriments conducted using -200 Desh deslimed fractions. hasYielded an acceptable gr~de ~f 27.6% P20S with a recovery of about 60~. !hehsul ts have been explained in terms of the sp '~cific ad -;orptiOIt characteris-tics of phosphate ions on apatite and the liberati.on size of the mineral.

I NTRO DU C'l' I ON

Mussorie rock phosphate from Uttar Pradesh, India contains about 19-20'P20s. It is necessary to upqrade its phosphate values to about 28-30' foreconomic use of this ore in the fertilizer in~ustry. Si.iceous pbo~ateores are generally beneficiated on an industria'. scale by a ~ stage flota-tion techniq~ using a.J.ines and fatty acids, respectively for silica basedgangue and phosphates. On the other hand, Mussorie rock phosphate whichis calcareous in nat,'re (containing about 15' calcite) appears not to beamenable to such Q flotation treatment. Mineralogical and ~~emica1 &~lysiEof a typical sample of this ore (Mussorie rock phosphate) given in Table Iclearly indicates its complex nature. .Even though the separation of ganguematerials such as pyrite and quartz could be easily achieved by flotation,~va1 of ca1cit£ fran phosphate posed the major proo1em .-;~ this case.'l!1is is believed to be due to tile similarities in th~ surface cher.ical aMelectrOkinetic properties of calcite and phosphate as a result of whic~ bothaiMrals respond similarly to cationic and anionic co~lectors. 'l'lis p:rob1e~is further complicated by the fact that the attempts to separate ~~osphate

~ -"

* Dept. of Metallurgy, Indian Institute of Science, Banga1ore, India

**Benry Krumb School' of Mines, ColuDbla ..University, Ncw Y<:-rk, -.':Y 10027, USA

from calcite even from thei~ synthetic mixture often failed under condition3where qood separation was p~.edicted based ~n sinqle Ddneral tests (Soma-s'mdaran, 1975). '!his has been suqqested tt) be '-ue to thf! infiuence of4lss.:>lved mineral species on the flotation properu.s .:>f each other (SaDa-8undaran, 1975, Ananthapadman..abhan, et al, 1977). 1-,::.;';:

Because of such problems in the beneficiation of the present.P'iaosP1~te, .:.~a 81'8tematiC study to obtain sol~tion condition& suchas pH, coll~cto~ co~...~Stration and depressant concentration was conducted in Hall!mond tube . U$i~ l ~ .£.1::

single a1ner£.18 and their synthetic mixtures. Subseq~nt s~eb.in.-Fage;'!;!;O~g'ren flotation machine using the crushed ore with additional steps to se~~~.;.ate the carbonaceous and sulfite gangue yielded a product having an acceEt-""i-::able grade of 27.6' P20S with 6°' recovery. Experi_nt with the single . ;_I~~

minerals, syntheti c mixtures and the ore are discussed in the following .-f"'- ...~sections with suggestions for further iq)roving the grade and recovery ~ '0

EXPERIMENTAL

Materials

Calcite. Iceland spar calcite Crystals purchased form Ward's Natural,:Science EstabliShment were crushed in a roll crusher to Obtain -35 +48-me~fraction for ~lotation studies.

~~te. Canadian fluoroa.patite containing about 5' calci~ was cr~dand then leached with dil. HNO3 (pH - 1.5) several times to remove the C8\- ~

cite from it. Complete removal of calcite was ensured by treating the min-.eral surface with Alizarin Red, 'which stains calcite prefenntially. 'Jhe-8ineral was then washed with triple distilled water several times till thepH of the s~rnatant reached a cons~t value of 6.9. -35 +48 fractionapati te was used for flotation experiments.

Phos~ate ore. Mussorie rock phosphate obtained from Pyrite Phosphateand CheDdcals, Ltd., India was crushed and deslimed to obtain -150 2sh(BSS) and -200 mesh (BSS) fractions for flotation feed.

Reaqents. Oieic acid reaQent qrade (UCP specifications) purchased frC8Fisher S' i.entific CODI>any was used to prepare potassium oleate solutions forsimple mineral and synthetic mixture structures. ~e stock solution was .

stored in the refrigerator under nitrogen atmosp~cre in order to prevent itSoxidation. Other dbemicals such as ~OB, XNO3' ~2003' ~3PO4 ~ere al: of ACSQrade purchased from FiSher Scientific C~any. Triple distilled water wasused for preparing _11 the solutions and in the case of oleate solutions .

deaerated triple distilled water was used.

*thods

Single mineral and synthetic mxture flotation experi~nt3 ~re carriedout using a aodified ~.alliD:)nd cell described elsewhere (Somasundaran andMoudgil, 1974). A special feature of this apparatus was the automatic con-trol of gas flow and stirring time which yielded reproducible resu~ts. Forflotation tests, about one gram of 'the m1.nera"1 was d.!slimed and condidoMd~~th the collector solutions in a 100 mI. volumetric flask by tumbling it at

3 -

a 1.ate of 17 rpm. At the end of ten minutes, the mineral and the solutionwere 'transferred to the Halli~nd tube for flotation. Purified nitroqen ata rate of 20 ml/min. was used for 10 sect)nds in all the e~e%'i_nts. pH oftne aineral 8\JPernatant solution was ~asured before and after condi tionin9and the latter was reported as flotation pH. Froth prrduct and t.'ie tailing8were dried and ~Jighed t, Obtain percent floated. In the case of synthetica1xt~8, beavy liquid separation ".1Bint bt!omOform was eDIPloyed for the ana-lysi8 for calculating the gra~ of the froth product and tailing.

Ore flotation tests were conducted with 250 91..8 saJlPle In laboratory8iM PagErqren subaeration machines. .

~ULTS AND DISCUSSION

Flotation of calcite and apd.U te as a functif)n of the concentration ofpotassium oleate under tlle s~ Iff conditions is g'iven in Figure 1. Appro..priate con.:entrations for tlle study of pH dependence of flotation werechosen fr m these results so tllat under the concentration rar.ae selectedflotation will be sensitive to addition of reaqents. 'nlus, lO-4M and 7.5 x10-6M oleate concentrations were select&d for calcite and apatite 'resp3ct-ively. Dependence of flotation of apatite on pH is shown in Figure 2.Maximum flotation is observed around pH 6-7. It is to.be noted tllat this isthe rang'e in which oleate-oleic acid soap coeplex, whic~ is possibly more8urface active ~mpared to other forms of oleate, is expected in .solution."!!lis ~rtant aspect of oleate chemistry on flotation behavior of mineralsis discussed elsewhere (Kulkarni and Somasundaran, 1975, Ku1k~ii, et a1,1977, Anantha;padmanabhan, et a1, 1978). Addition of .{3PO4 (lC H) to. the8ystem, as can be noted from Fiqure 2, has CO1Ji)letely suppressed tlle apatiteflotation under all the pH conditions considered. It would be interesting'to look at the effect of potassium phosphate on the flotation properti~s ofcalcite (see Fig'Ure 3). Sig'nificant decrease in calcite flotation due tophosphate addition is observed only in tlle alkaline range. ~is res~tcoai)ined with earlier observations on the phosphate effect on apatite flo-tatior. sug'g'ested a sche~ for ca!Cite-aphtite separAtion whidl would involveoleate flotation of calcite in the presence of potassium phospha~ as adepressant for apatite. Bow...ver results obtained earlier for the effect ofdissolved ~neral species on the flota~on properties of calcite and apatite(Ananthapadmanabhan and SoJr J.sundaran, 1977) had shown flotation of both cal-cite L~d apati~e to be depressed by tlle aissolved species of both the m1Der-a1s, but only in the allta1ine ranqe for calcite. Since tlle overall aim 1sto depress the flotation of apatite, the effect of dissc.1ved species in theacidic rang'e is to be consid£red beneficial for the present separation.Under such conditio11s, it should be possible to selectively float ca1c.te anddepre:3:) apatite in t&'1e acidi... range. '!his has been confirDed during' the8tUdies with syntlletic mixt\lres which were conducted with certain DK)difica-tions. When the mineraL mixture was treated witll oleate solutions for enminutes, is in tlle case of single mineral test3, only abOut 40% of the epa-t".ite was depressed, whereas reducing' the conditioning time to one minute im-proved tlle reoovery to 90% with all the calcite in the froth product (see. .FJ.gure 4).

It would be interesting to investigate the reasons for the selectivedepression of apatite by phosphate in the acidic reg~ou. 1he depression of

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- --~pati ~A by Phosphate (H2PO4IHPO4 ) could be due to the specific adso~tior.of phosphate ions on the Ca-sites of the apatite surface (Somasundaran and'Aqar, 1972) preventinq the oleate adso~tion. Similar mechanism can be ex-pected to operate on the c~cite surface also. On ~e other hand, theforaation of llic-obubbles of carbon dioxide on ~e calcite surface in theacidic region can possibly enhance the bubble-particle attat.'hDient for flota-tion.' "

After the chemical conditions were established for the selective flota-tion of calcite fran apatite, st\dies were extended to the beneficiation ofthe ore. Initial tests were carried oUt using the deslimed -150 ~sh frac-.tion, these re~ul ts a~ a given in Figure s. Even though the recovery ob-tai~d was abOut 70', the P20S content of the. non-floated concentrate wasless than 24', far below the acc(~ptable value. Even. a three stage flotatJ.onusing terpineol for carbonaceous materials, potassium ethylxanthate fu~pyrite and oleic acid for calcite with K2BPO4 as the depressant for phOS-Plate did IXIt yield satisfactory results. 'rests were alsf' perfo~d withhydrofluosilicic . acid and starch instead of K2HPO4 as depressants for phOS- .Plate, but..the resultL were inferior to those obtained using K2HPO4. At tJ11s.tage, the feed size was reduced to -200 mesh (again deslimed) and. a similarthree stage flotatJ.on scheme using terpineol, potassium ethyl-xanthate,oleic acid and dipotassiU!ft hydrogen phosphate w~s employed. '1!le xesults are9iven in Figures 5 and 6. Percent recovery and grade are given .as a functionof concentration of K2HPO4 in the fo~r aM as a function of the concenflra-'.t1on of oleic acid in the latter. Increase in the amount of K2HPO4above 3 kg/ton did not produce any improvement in thl' recovery. Xncrease inoleic acid concentration decreased the -recovery but did i:rD;.)rove -the grade.~st results, under the conditions considere'd here, ha\.'e yielded anacce~le ~ade of 27.6' P20s with 60' recovery. The improvement in gradeobtained by reducing the feed size to -200 mesh could be due to the betterliberation achieved under these conditions..

It should be ~ntioMd here tllat tllp.se results support th~ contentiOnthat Ball!mond tube results are extremely valuable in understanding t-hechemistry of the system. Ar'::"ueEnts often heard against the B8.LliD:>nd t1:i>ethat uses only a one gram mineral sample are unfounded.

Further improvements, in both qrade and recovery ~e possible by addingcleaning and scavenging steps to the calcite flotationd.rcuit.

Experiments were also Conducted as a function of the condi tioning ~with KPO4' as this was found 'Co be an important par~ter during the "Syn-thetic mineral studies. '!be results given in Figure 7 sugge.sted five minutesto be the optimum conditiotdng time. Here again, at higher co~tioning tiI8,percent recover-.i was found to decrease, even though an improv~nt in gradewas observed.

CONCLUSIONS. .

g31ecti"e flotation of calcite from apatite using oleic acid has been.successfull:" attempted by depressing the phosphate wlth dipotassilml hydrogenphosphate. Olemical conditions for selective flotation were evloluated firstby conducting single mineral and synthetic mixture flo'.:ation tests. A three

- 5 -

.

Stage flotation sche. developed subseque.tly for the beneficiation of Mus-aorie rock phosphate (Uttar Pradesh, India) rmploying terpineol for carbon-aceous material, potas3ium ethyl-xanthate for pyrite and oleic acid in .com-bination with di20tassi1B hydrogen phosphate for calcite yiel4ed a productcontaining 27.6' P20S with 6°' recovery. Inclusion of cleaninq and s~Aveng-1ng steps in calcite flotation circuit should further improve both the gradeand recovery of phosphate.

ACKN~OOMEN'JS

'111e authors acknowledge the partial support of the U.S. National ScienceFoundation and the Pyrites, Phosphate and O1emicals, Ltd. and the technicalassistance of Mr. T. Wong.

REFERENCES

Ananthapadmanabhan, K.P. and Somasundaran, P. (1977) -'1he;-.Role of UnavoidableChemical Species in Calcite/Apatite Flotation, n paper presented at the lO6th

Ann. AIME ~eting, Atlanta, February 1977.

Ananthapadmanabhan, K.P., Somasundaran, P., and Healy, 'l'.W. (1978) 8'!be Oleu.-istry of Oleate and Amine Solutions in Relation- to Flotation,8 paper presentedat. the lO7th A.-m. AIME ~etin9, Denver, March 1978.

x;u1karni, R.D. and Somasundaran, P. (1975) "Kinetics of Oleate AdSorption atthe Liquid/Air Interface" and Its Role in Hematite Plotatton,. Mv. i.! "Inter-facial Phenomena of Particulate/Solution/Gas Systems,. P. So~~undaran anda.B. urieves, eds., AIOlE Symp. Ser.,"V. 150, 124-133.

EuIkarni, R.D., Somasundaran, P., and Ananthapadm~nahhan, K.P. (1977).Flotation ~chanism Based on IonoJX¥:>lecular Complexes,. XII Int'l. Min!.Processing Congress, IRON-II, Sao Paulo, Brazil, 80-94.

8Mussorie Phosphate: A Technical Note on the ~posit and Beneficiation Char-acteristics," Pyrites, Phosphates and Chemicals Ltd., India.

somasundaran, P. and Agar, G.E. (1972) "Further streaming- Potential Studieson Apatite in Inorganic Electrolytes," SMF, AIME, 252, 348-52.

somasundaran, P. and MoOOg'il, B .M. (1974) "'l11e Effect of Dissolved Hydro-carbon Gases in Surfactant Solutions on Froth Flotation of Minerals,~ J.Coll. Interface Science, 47 (2), 290-99.

Somasundaran, P. (1975) -On the Problem of Separation of Calcite from f'..ai-careous Ap~tite,. Seminar on Beneficiation of Lean Phos ates with C4rb0nateGanque, nth Int'l. Minl. Processing Congress, Calg1iari, 2, 155-6.

TABLE 1

Q\emical Analysis of oreApproximate MineralogicalCoD()Osi don-

19.9'4.6

0.8

6.7

45-48\ ..

12.14

Collophane

Muscovite

Serici te and

Clay

~rtzCal-:ite

Doloa1 te

Pyri te

r .i~ni te

7.10

14.16

6-8

6-7

2-3

P20S

Fe203

A1203

SiO2Cao

MgO~ss on

];pinon

s

~..1IOM..~nrt0~gn..~.rt..-80~1...00...

.g0~g;....0gJ!.0~0..aa.I:-~B

.

it!.~

0r--r'1o.J>

~

-tr"1n0zn-r"10z

I-t

0

~»-t0Z. -

~o.

...

-0..,.

-9.-.

.(')»r(')-:-tf"

.»~~.-tr'1 N0

. T

I T

-0:J:Ic.o.c.o1+0.-

-4-~rT1I-0cnrT1

('). ~5 m0I

nA:

0 I

zoor. r'1

-I»--I~

fT1

fT1I-0~-IU>

.

. -00

~,~,~~~F

LOA

T

100. I I I I I - ,I . NO DEPRESSANT APATITEI

I "f' kS PO4 104M k-OlEATE -.2 x 166M

- 3x162M-80KNO3

~0 60LI.J

~0-J 40tA.

-

-

20

4 5 6 7 8 9 10pH

Figure 2 - Bffect of E3PO4 on apatite .flotation.

~.~

~~").~

:CALCITE

80 -K-oleote 10- .'M

-

.-:'

8TDW20 . PHOSPHATE IONS(10-4M) -

I I I I I I00 2 4 6 .8 10 12 14

pH

Figure 3 - Effect of E3PO4 on calcite flotation.

~~~,~.~

0 2 10 124 6 8T'ME - MINUTES

Pi~ 4 - Effect of condi tioni.D9 time on the recovery of

apatite frC8 a calcite-apatite synthetic mixture.

I -n-.. v~

I90

,-- - ~...,.., '-' ~ (~i1q-~~-O~-r:;=1v~_:;~ DO!100.- . ,;, ,., )':,1' i ' I .

~~ ! i-\r~'-~(..,,- ,I ,'c. .. MUSS.ORIE PHOSPHATEf\1 OO~- -- t1331 i

~ OLEIC ACID (~"-:-l-KgtTon.~O Sc-l t

Cf)ND. TIME - ;~K2 H~a4 -r'5 MT~)c.1 H s~ !

,...~ -;:-'.:-, - Ob~I,-G,~CID'551MTSft10J,,:-" ;j'II- PH -c 6 .~ . . "",!, -" --; ', . i

. ~ . ,,' " - I. I ',',;\, ;'"" '_"1_..1__'.- !

t .'"'- ~-.. \.'f;;t

\80

~

-J. 1"",. ",' !I

.-~.,.-.70 ~: \

: --,'"

- -;.. .

,"'-- t-; (: -~,I "I.:

'

60

;',.".~~

~

--

L~ y... --

It)26 0

~II ~0

30 -0-. --- ,)

20J. r ~\..;~ -I~ c c C=~"b--C ~"

c . "c10 "22

~"-<'~.~'i.

~."

- FEED. - 200 MESH - BSS

(22.07 % P2 °5)

FEED.-150 MESH-SSS ;- - (18.4~/o R05~ "---":"-~-", L___~__L_." t(:~

0 ~3" - "~

4 202 ... "-. i'

.'. 1<2;1 Ii p;.d4'~".KO'l(ton

Figure 5 - Rec~ry aM qrade of ~~ori~~~?~I.>~~e:¥ . f~ctic"n of J..~ 4

Concentration.

>- 500:tIJ>0-,,' -(,) 40tIJ ,a:: :

MUSSORIE PHOSPHATEFEED - -200 MESH (BSS)

(P205 - 22 .07%)- 3Kg ./Ton- ~2HPO4 - 5MTS.

OLEIC ACID - 5 MTS.

90

K2 H PO4CONDo TIME60

~

70 .

60>-Q:~>

0(.)L&Ja:

50 -

~0 -40

2630 . -s

20 -

10 -

O' I I I I I I 1200.2 0.4 0.6 . 0.8 1.0 1'.2 1.4

OLEIC ACID, Kg /Ton

Piqure 6 - Recovery and qrade of Mussorie phos~~ate as a f~ction of

Oleic acia cancentra.ion.

."0

~~0

100

90

OLEiC ACIDK2 H PO4CONDo TIMEpH - 6.5

80- 1 Kg I Ton

-- 3 Kg I Ton

- OLEIC ACID - 5'MTS.

70.-"'..-".--'

.60 .

>-0:W>0(..)W0:

-50:

~0 -400

00

126I30 -

-20

-10

~~~~

~,~,~

0 0 ~ * ~ ~ 1 ~ ~ 10

CONDITIONING Tlt.1E IN KlHPO4- MTS.Fiqure: 7 - Dependence of recovery and qr.,de of Mussori~

phosphate on cordi tioning time in J::2BPO 4.

MUSSORIE PHOSPHATEFEED - -200 ~J1ESH (BSS)

~a,.N~0