This paper deals with the results of flotation studies carried  towards   pre-concentration  of  a  low-grade

uranium ore sample from Domiasiat, Meghalaya.  A comb-ination of potassium amyl xanthate, cupferron and light diesel oil was used as collector for flotation of uran-

ium bearing minerals in the sample. The effects of vari-ous process parameters were studied. Under the optimum conditions the flotation concentrate weighed about 35 % with over 90 %  recovery. Flotation  with  classified / deslimed feed also resulted in  similar  metallurgical results. Use of diethyl hexyl phosphoric acid, alamine 

336 & tri-butyl phosphate in combination with potassium amyl xanthate and light  diesel oil, as  the  alternate reagent  scheme,  also gave  reasonably  high  uranium 

recovery

Chattopadhyay, A

Maulik, S C

Pathak, P N

Sengupta, P L

Singh, Ratnakar

English

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International Conference on Challenges in Coal and Mineral BeneficlationFLOTATION STUDIES ON PROCESSING OFA LOW GRADE URANIUM ORER. Singh, S.K. Sengupta, P.N. Pathak, A. Chattopadhyay and S.C. MaulikNational Metallurgical Laboratory, Jamshedpur, IndiaABSTRACTThis paper deals with the results of flotation studies carried towards pre-concentration of a low-gradeuranium ore sample from Domiasiat, Meghalaya. A combination of potassium amyl xanthate,cupferron and light diesel oil was used as collector for flotation of uranium bearing minerals in thesample. The effects of various process parameters were studied. Under the optimum conditions theflotation concentrate weighed about 35 % with over 90 % recovery. Flotation withclassified/deslimed feed also resulted in similar metallurgical results. Use of diethyl hexyl phosphoricacid, alamine 336 and tri-butyl phosphate in combination with potassium amyl xanthate and lightdiesel oil, as the alternate reagent scheme, also gave reasonably high uranium recovery.INTRODUCTIONThe uranium is the basic raw material for a nuclear energy programme. In India, uranium ore isprocessed essentially by hydrometallurgical route. The conventional process involves sulphuric acidleaching of uranium from the ore, ion-exchange concentration followed by precipitation of uranium asmagnesium diuranate. A pre-concentration of the ore by physical beneficiation method is expected toreduce the high acid consumption in leaching of the low grade ore and would also be helpful in safedisposal of tailings [I].In Meghalaya occurrences of sandstone type uranium mineralisation is reported from Domiasiat. Aneconomic explotation of this deposit is desirable. At the instance of M/s Uranium Corporation of IndiaLtd., Jaduguda froth flotation studies were carried out on a low-grade uranium ore sample fromDomiasiat, Meghalaya. It was envisaged that froth flotation would be helpful in pre-concentration ofthe ore reducing the load on downstream hydrometallurgical steps. This paper presents the salientresults on the flotation of the low-grade uranium ore sample from Domiasiat, Meghalaya.MATERIALS AND METHODSOre SampleThe sample used for the studies was all passing below 1680 microns . It assayed 0.052% U308. Theganulometry and the uranium distribution in different size fractions of the sample is shown in Fig. 1.ReagentsCommercial grade potassium amyl xanthate (KAX) and analytical grade cupferron from E. Merck(India) Ltd., Mumbai with light diesel oil (LDO) were used as collector for flotation of uranium ore.Laboratory grade methyl-iso-butyl carbinol (MIBC) was used as frother while commercial gradesodium silicate (SS) was used as depressant/dispersant for siliceous gangues . Laboratory gradesulphuric acid and sodium hydroxide were used for maintaining pH of the pulp.135MethodsThe bench scale flotation experiments were carried in standard Wemco Fagergren LaboratoryFlotation Cell. For this purpose 500 gram -1680 micron ore sample was wet ground in laboratory rodmill at a pulp density of 66% and floated after conditioning with the flotation reagents at a pulpdensity of 20%. All the products from the flotation experiments were assayed for %U308 by standardspectrophotometric method involving uranium extraction with tri-butyl phosphate.RESULTS AND DISCUSSIONChemical, Ganulometric and Mineralogical CharacteristicsAs mentioned earlier the ore sample analysed 0.052 % U308. The particle size and uraniumdistribution in different size fractions of -1680 micron ore sample as give in Fig. 1, showed thepreferential concentration of uranium values in the fine size ranges, particularly below 37 micronfraction contained 68.4 % of the uranium distribution. The X-ray diffraction studies carried out on thehead sample indicated a broad picture of the various mineral phases. The sample was predominantlymade up of quartz while other minerals like pyrophyllite, kaolinite, muscovite, paragonite,ferricolumbite and rutile occur in minor proportion to traces. The presence of radio-active mineraluraninite was indicated by X-ray spectra. The X-ray spectrum of the sample is shown in Fig. 2Particle Size, micronFigure 1: Particle size and uranium distribution in different size fractions of crushed sample.1700^MOO.roo1}I•I T7O^x 1{I()L) C I d.I ISM II.cc^lE :41 ^L_ E.acp . I(] : (JUAr [Vy • PA . LI ItM ' kAOLOLINSWIFMu' MUsco"TEfr' 0-A4ACOE . UMFITEV FMAAGETT!W- UQAWNI TE.0 UQANOCIQCIIEQu - WU71LEOIVfWACTION ANGLf1701Figure 2: X-ray diffraction pattern of uranium ore sample.136Effects of Granulometry on Flotation of Uranium MineralsExperiments were carried out to study the effects of granulometry on the flotation behaviour ofuranium bearing minerals . For flotation with potassium amyl xanthate pH of the pulp was maintainedat 8.5 while for the combination of cuferron and light diesel oil, pH was 4.5. The results of theseexperiments are shown in Fig. 3. As we can see from the data shown in Fig. 3 that due the betterliberation an increase in fineness of the feed from 30.6 % to 35. 1 % increased the uranium recoveryfrom 85.6 % to 92.6 % respectively. Similarly the yield has also increased from 24.7 % to 35.6 %. Afurther increase in fineness of the feed and hence a decrease in the particle size shows a marginalimprovement in recovery but at the cost of loss in selectivity as evident by the sharp increase in yieldand a corresponding decline in grade of the concentrate [1]. An increase in the yield of the concentrateat finer size with increasing fineness of the feed is mainly due to increased gangue recovery byentrainment and entrapment phenomena and the mechanical carry over [2]. Based on these results afeed with 35.1 % -74 micron was considered suitable for uranium recovery from the sample.at 120 ,m 100 ^80604020250Recovery IYield35 45 55Wt. %-74 micron in Feed65Figure.3 : Effects of granulometry of feed on flotation of uranium bearing minerals.Flotation of Classified/Deslimed FeedFrom the size-wise chemical anaiysis of crushed product and ground flotation feed it was found thatthe sample showed a preferential distribution of uranium values in the finer size fractions, particularlyfractionbelow 37 micron contained uranium values more than 60 % [1]. So it was felt that there exists apossibility of separating uranium rich finer fraction and floating the sand against the direct flotation ofthe ground bulk feed. The classification/desliming of the flotation feed is also expected to remove thefine particles which are known for slow flotation rate and thereby improving the overall flotationefficiency [3,4]. In order to examine these facts the ground flotation feed was classified using 37micron screen and sand was floated. Another flotation experiment was carried out under the identicalconditions using a manually deslimed feed. The desliming of the feed was performed after suitablescrubbing in laboratory mechanical agitator. The uranium recovery from the classified and deslimedfeed are shown in Fig. 4. As it can be observed from the data shown that classified and deslimed feedgave uranium recovery of 26.5 % and 22.7 % respectively. When the uranium rich fines (-37 micronfraction/slimes) are mixed with the flotation concentrate the resulting uranium recovery is -92 % inboth the cases which are similar to those obtained by direct flotation of the ground ore as shown inthe same figure. So in the present case from the process point of view classification/desliming of the137feed is not essential but this offers an option for reducing the load on flotation by splitting the feedprior to flotation and thereby reducing cost on reagents etc.n From Fine Fractionn By FlotationFigure 4 : Flotation results with classified /deslimed feed against normal feed.Effects of Xanthate Dosage on FlotationPotassium amyl xanthate has proved useful in flotation recovery of uranium bearing minerals from thepresent ore sample . In order to study the effects of the variation of dosage of xanthate on the uraniumrecovery and the flotation selectivity, experiments were carried out varying the xanthate dosage from0.075 kg/t to 1.2 kg/t. For these experiments flotation with the combination of cupferron and lightdiesel oil was discontinued. The results of the experiments on xanthate dosage variation are shown inFig. 5. It was found that although there was a progressive increase in the yield of the flotation productwith an increase in the xanthate dosage from 0.075 kg/t to 1.2 kg/t [1,5] but as it is evident from theFig. 5 that almost there is no improvement in the uranium recovery. The increase in the yield wasmainly due to loss in selectivity of separation leading to increased recovery of gangues with higherdosage of xanthate. SoO.075 kg/t xanthate (alongwith cupferron and light diesel oil) was consideredsuitable for flotation of uranium bearing minerals from the sample.70006050403020102 4 6Flotation time, mina8Figure 5 : Uranium recovery under varying dosage of xanthate.138tVariation of Dosage of Cupferron and Light Diesel OilAs mentioned earlier cupferron and light diesel oil were used alongwith potassium amyl xanthate ascollector for flotation of uranium bearing minerals . As discussed above xanthate was effective inrecovering more than 60 % of the uranium values from the sample. This was attributed to theassociation of pyrite and carbonaceous materials with uranium bearing minerals in the sample [1]. Butfor further improving the uranium recovery, cupferron, a uranium chelating agent, was used. Lightdiesel oil was used as a chain extender alongwith cupferron. Experiments were carried out to examinethe effect of the variation of dosage of cupferron and light diesel oil on flotation of uranium minerals.The dosage of cupferron was varied from 0.312 kg/t to 1.25 kg/t while for light diesel oil the samewas from 0.462 kg/t to 3.6 kg/t. The results are shown as the additional uranium recovery (over thosealready recovered by flotation with xanthate) against the dosage of the reagents in Fig. 6. As it can beobserved from the resultse summarized in Fig 6 that 0.312 kg/t of cupferron is not sufficient and anincrease dosage to 0.625 kg/t improves uranium recovery. But a further increase in cupferron dosageshowed a decline in uranium recovery. Again for light diesel oil, an increase in dosage from 0.462 kg/tto 1.8 kg/t, there is some improvement in recovery but further higher dosage does not lead to anyimprovement3025201510CupferronLDO0 1 2 3 4Cupferron / LDO Dosage, kg/tFigure 6 : Effects of cupferron and light diesel oil on uranium recovery.Effects of pHpH governs the charge on the mineral surface and plays an important role in the adsorption of theflotation reagents and hence floatability of minerals . Normally xanthate is used in alkaline pH forflotation of most of the metallic sulphides but for pyrite slightly acid circuit is preferred. On the otherhand cupferron forms complex with uranium ion in the reduced state (U`) in a strongly acid medium.Good recovery of uranium is reported between pH 4-6 [6-8]. Marabini finds high recovery ofpitchblende for Hallimond tube flotation over pH 0-4 [9]. But at the same time considering thepresence and association of uranium phases and the varying degree of floatability in the present casethe effects of pH was varied in a wide range. The results of pH variation is shown in Fig. 7. As it canbe seen from the results that though a reasonably high recovery is possible in a wider range of pH buta slightly alkaline pH for flotation with xanthate and slightly acid circuit for flotation with cupferron ispreferable. The best results obtained at pH 8.5 for flotation with xanthate and at pH 4.5 for cupferronflotation.139Alternate Reagents SchemesXanthate is a commercially established collector and is also known as an economical flotation reagent,which has shown its efficacy in the flotation of uranium bearing mineral species in the present oresample.94Recovery--*-Tailings Assay0.008865.5/5.5 7.5/8.5 8.5/4.5 8.5/8.5 10.5/4.5pH of Flotation Pulp (Xanthate /Cupforron)0Figure 7 : Effects of pH on uranium recovery and assay of tailings.On the other hand application of cupferron has been limited to laboratory flotation studies and it isconsidered costly for commercial applications. The reagents like diethyl hexyl phosphoric acid,alamine 336 and tributyl phosphate, because of their tendency to form complexes with uranium, areused in solvent extraction of the uranium [10]. So in order to develop alternate schemes, studies wereundertaken using these reagents as flotation collector for uranium bearing minerals in combinationwith light diesel oil. It was interesting to note that a reasonably high uranium recovery could beachieved with above reagents alongwith potassium amyl xanthate [1,5].CONCLUSIONSFlotation studies were carried out on a low grade uranium ore sample from Domiasiat, Meghalaya.The sample assayed 0.052 % U308. and it showed a preferential concentration of uranium values inthe fine size ranges . Use of potassium amyl xanthate in combination with cupferron and light dieseloil as collector for flotation of uranium bearing minerals resulted in a pre-concentrate with a yield of- 35 % and uranium recovery over 90 %. Flotation results with the alternate flotation reagent schemesinvolving diethyl hexyl phosphoric acid, alamine 336 and tri-butyl phosphate in combination withlight diesel oil and potassium amyl xanthate were also found encouraging. Pre-concentration of thelow grade sample by froth flotation can reduce the load on the hydrometallurgical extraction ofuranium.ACKNOWLEDGEMENTSThe authors sincere thanks are due to Prof. P. Ramachandra Rao, Director, National MetallurgicalLaboratory, Jamshedpur for kindly permitting to publish this paper. They wish to thank to themanagement of M/s Uranium Corporation of India Ltd., Jaduguda for providing the financial supportto this project. They also thank them for supplying the necessary uranium ore samples and carryingout the chemical analysis of the flotation products.140REFERENCES1. Singh, R., Sengupta, S.K., Pathak, P.N., Chattopadhyay, A. and Maulik, S.C., (1997), Studies onPre- concentration of Domiasiat Uranium Ore by Froth Flotation, Investigation Report, NML,Jamshedpur, India, pp. 1-37.2. Mehrotra, S.P. and Singh, R., (1993), Role of froth processes in flotation , J. Metals, Materials &Processes, 6, 195-216.3. Singh, R. Rao, S.S., Maulik, S.C. and Chakravorty, N., ((1997), Fine particle flotation- Recenttrends, Trans. Ind. Inst. Metals, 50, 407-423.4. Singh, R., Pradip and Shanker, T.A.P., Selective flotation of Maton (India) phosphate ore slimeswith particular reference to the effects of particle size, Int. J. Miner. Process., 36, 283-293.5. Singh, R., Sengupta, S.K., Pathak, P.N., Chattopadhyay, A. and Maulik, S.C., (2000), Pre-concentration of Domiasiat uranium ore by froth flotation, Proceedings of National Seminar onMineral Processing Technology (MPT- 2000), Nagpur, pp. 25.6. Muthuswami, S.V., Vijayan, S, Woods, D.R., and Banerjee, S., (1983), Flotation of uranium fromuranium ores in Canada, Part I- Flotation results with Elliot Lake uranium ores using chelatingagents as collectors, J. Chem.Engrs., 63: 728-744.7. Muthuswami, S.V., Vijayan, S, and Woods, D.R.,(1985), Flotation of uranium from uranium oresin Canada, Part II- Cupferron adsorption on uranium oxide, quartz, illite and a uranium ore fromElliot Lake, J. Chem. Engrs ., 65: 650-661.8. Singh, A.K, Padmanabhan, N.P.H., Sridhar, U. and Rao, N.K., (1992), Proceedings of NationalSeminar on Research and Process Development in Mineral Preparation, NML, Jamshedpur, pp.217- 224.9. Marabini, A.M., and Rinelli, G., (1973), Flotation of pitchblende with a chelating agent and fueloil, Trans. Inst. Min. & Metall., C225-C228.10. Ritecy, G.M. and Ashbrook, A.W., (1979), Solvent Extraction : Principles and Application toProcess Metallurgy, Part II, Elsevier Publication, New York, pp. 453.

Floatation Studies on Processing of a Low Grade Uranium Ore

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Floatation Studies on Processing of a Low Grade Uranium Ore

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