ABSTRACT : R & D studies were carried out at NML using Acidithiobacillus ferrooxidans (Ac.TJ in

column for the bio-recovery of uranium from the low-grade uranium ore containing 0.024% U308 of

Turamdih Mines, Singhbhum. A recovery of 55 .48% uranium was obtained in bio-leaching as against --

44.0% in sterile control in 30 days at 1.7pH in a column containing 2 . 5kg ore of particle size mainly in the

ra,., 5-1mm . In the large scale column , leaching with 80kg ore of particle size -0.5cm, uranium biorecovery

was found to be 69.8% in comparison to a recovery of 55% in control set at 1.7 pH in 50 days. The

uranium recoveries followed indirect leaching mechanism

Abhilash,

Kumar, Vinay

Mehta, K D

Pandey, B D

Tamrakar, P K

English

eprints@NML

Amenability of Low- grade Uranium towards ColumnBioleaching by Acidithiobacillus FerrooxidansAbhilash *, K.D. Mehta*, V. Kumar*, B.D. Pandey*' and P.K. Tamrakar***MEF Division, NML, Jamshedpur-831007, India **CR&D Dept., UCIL, Jaduguda, Jharkhand, India'E-mail: bdpandey@ nmlindia.orgABSTRACT : R & D studies were carried out at NML using Acidithiobacillus ferrooxidans (Ac.TJ incolumn for the bio-recovery of uranium from the low-grade uranium ore containing 0.024% U308 ofTuramdih Mines , Singhbhum . A recovery of 55 . 48% uranium was obtained in bio-leaching as against --44.0% in sterile control in 30 days at 1.7pH in a column containing 2 . 5kg ore of particle size mainly in thera,., 5-1mm . In the large scale column , leaching with 80kg ore of particle size -0.5cm , uranium bio-recovery was found to be 69.8% in comparison to a recovery of 55% in control set at 1.7 pH in 50 days. Theuranium recoveries followed indirect leaching mechanism.1. INTRODUCTIONAs the high-grade ore deposits are becoming rare,the importance of processing low-grade ore isincreasingly being recognized . Metal-solubilization processes were believed to bechemical reactions mediated by water and oxygenuntil 1947, when bacterial catalysis of ironoxidation and sulphuric acid formation in minewaters was demonstrated [Colmer et al., 1947].Today bioleaching is an actual economicalternative for treating specific mineral resourcesuranium as a result of rapid growth of thenuclear power industry. Presently the world'spower reactors with combined capacity of nearly370 GW, require about 68,000 T/yr of uranium.Due to higher burn-up of fuel, demand is steadilyincreasing and so is the need for bio-leaching oflow-grade uranium ores.In bio-hydrometallurgy of uranium [Guay etat., 1977; Tuovinen,et al.,1984; Mather et al.,2000; Abhilash et al.. 2006], the insolubleuranium (IV) is oxidised to the water solubleuranium (VI) by bio-oxidation of pyrite of orewith the generation of ferric ions as:U0, + Fe1(SO4)3 -4 UO,SO4 ±- 2FeSO.4 . , . (1)Leaching in column simulates the flow of a liquidpercolating through a mass of material by gravity.The lixiviant also penetrates into microfissuresand micropores of the ore reducing the need forenergy consuming crushing and grinding steps[Lizama et al., 1989; Muiioz et al., 1995]. Thispaper discusses the results on bioleaching ofIndian low grade uranium ore by A . J rrrx,^Yicko sin a laboratory and a large scale column.2. MATERIALS AND METHODSLow grade uranium ore (0.024% - 0.03% U,Ox)was collected from Turamdih mines. Jharkhand,India. A representative sample was prepared byconing and quartering for chemical analysis byFluorimeter (UCIL) and AAS (Model: GBC908BT) for other metals (NML). The chemicalcomposition of the ore for large scale experimentswas 0.0278% 1J7Os. I0.64°n Fe. 0.0031o Cu.0.0480,0 Ni, 0.056% Co, 47.4% SiO,, 1.085%CaO. 0.383% TiO,. 0.168% S and 15.5% AI,O;.For laboratory column, the ore contained 0.024%U1 1.0,511 o Fe, 0.090% Cu. 0.0491oNi. 0.058% Co. 47.6°.0 SiO,. 1.0')20o CaO.0.412% FiO,, 0.172% S and 1 5 . 5 ° x . A 1,0 .X RI )analysis of the ore showed silica. alumina andmagnetite as the major phases while aluminiumsilicate, ferro-silicate and hematite being minorphases. Uranium was present as uranitite (1_10,).The ore with proper sizes ^sas packed in 2.5 kg7346Iaboraton column 1-lnmm to 60mesh: 200g• -Jmm to yI mm: 2.0kg and 5mm to 4mm: 300g].For large scale experiments (80k(.g) only twofractions such as 0,5cm (70kg) and 2.5cm (10ku)were used. l3^reteria used in this work wereisolated from the mine water of Thuramdih mines.The isolated -(C. T/'was mierobiologieally and wasgroin in QK medium and sub-cultured at I.7pHand 35`(' (Silverman, 1959). For column leaching,10° 0 (V culture was adapted on 5% (www/v) ore at1.7p11. In case of chemical leaching, addition ofmercuric chloride acted as bactericide.Fig. I shows the schematic diagram of thelab scale column set-up for 2.5kg ore leaching.The laboratory column was fabricated from 0.2cmthick Plexiglass , 75cm high and 6 . 5cm I.D. Ahigh density support rubber cork with a hole wasplaced in the bottom of the column . The column\k as sprayed with the bacterial solution (10L)using a metering pump at the rate of 3L/h, whilere-circulating the leach solution . The leachant had10% inoculum (cell count of 6.4 x 10' cells/mL).In large scale , the column (rubber lined MS) had80kg ore while spraying 360L leachant at the flowrate of 551./h containing 10%inoculum (celldensity of 6.9 x 105 cells/rnL).- .^ osomI ;I^^-rteEMeteringPumpN\Nreactorirri,qiii . 7:III "'1171 "1117711 7"7 IMineral Processing Technology (MPT 2007)Feed and leach liquor Were sampled and analyzedto estimate the extent of metal dissolution, Cellcount was determined in a Petroff-Hauser counterwith Leica biological microscope. Fer wasanalysed by titration against K2Cr207. The p11 ofthe leach solution was maintained on alternatedays. Redox potential (Eh) was measured againstSCE,Fig. 2: Schematic of 80 kg Scale ColumnReactor3. RESULTS AND DISCUSSION3.1 Column Leaching at 2.5 kg ScaleThe effect of pH on uranium recovery wasevaluated with equal load of ore. The uraniumleach recovery showed increasing trend with timewhich may be correlated to increase in bacterialcell count from 6.5 x 10' to 1.3 x 109 cells/mL atpH 1.7. Thus uranium bio-recovery was found tobe 58.91°=o as against 56.820% at pH 1.9 in 40davsAmenability of Low-grade Uranium towards Column Bioleaching ... 3471701.3x109158.91 601501 40 030lox1000 10 20 30 40 50Do"Cell counVmLt Uranium Recovery)Fig. 3: Change in uranium biorecovery with cellcount at pH1.7 using 2.5 kg orer 1200 66.8• 60/^^ r10000 1•0 8x1o 100800 + 40J 0600 + 30-r Celt cant/mLOY 400E20 `-t-% Uranium bcrecoceryU 200 10 I1- 0-0 10 20 30 40 50DaysFig. 4: Change in uranium biorecovery with cellcount at pH1.9 using 2.5 kg oreVariation of Eh (mV) and change in Fe(ll)levels in bioleaching columns at 1 .7 pH is shownin Fig.6. The Eh increased from 530 to 635mVwith corresponding decrease in Fe (11) to 0.12g/Lin 40days time , showing consumption of Fe(lIl)in leaching . In case of control leaching , change inEh was found to be in the range 350 to 564mV in40days which was almost constant from 20th dayonwards as against a steep rise in Eh beyond32days during bio-leaching at 1.7pH. At pH 1.9,Eh varied from 540 to 623mV.Fig. 6: Variation of Eh (mV) and change inFe +concentration in column bioleaching at1.7pH3.2 Column Leaching at 80 kg Scale403020 11000 10 20 30 40 50Day:Fig. 5: Uranium recovery in control leaching atpH1.7 using 2.5 kg oreThe extraction rate increased particularly rapidlyat the lower pH of 1.7 where formation of jarositeprecipitate was very light. The jarosite formationappears to limit the rate of uranium solubilisationby hindering the permeation of soluble reactantsthrough this layer.Column bioleaching on large scale was carriedout in two columns. one for bioleaching and otherfor control leaching with a flow of lixiviant at -9h/day basis for 50days. The results reported inFigs. 7-8 showed an appreciable bio-recovery of69.8% at I.7pH against a control recovery of 55%in 50 days with a respective rise in Eh from 325 to638mV and 332 to 614 mV.lndirect leachir12mechanism is thus responsible for uranium bio-recovery. The cell count of Tf increased from63 x 107 to 2.66 x 1010 cells/mL in 50 days,which may be responsible for the rise in redoxpotential due to the oxidation of Fe (11) andcorresponding increase in bio-recovery ofuranium (Fig. 9). Thus, uranium bio-recovery inlarge column was higher than those in laboratorycolumn.34 8 "," ",.V"; Mineral Processing Technology (MPT 2007)700600500E 400 sw20r-1 00- 80638mVk- =x69.8% - 70- 6050 0Q -x- Redox Potential40 `.2 -r- % U Bio-recovery . Im30 n. 20100- -.- 00 20 40 60 80DaysFig. 7: Change in uranium biorecovery with Redox Potential at pH1.7 using 80 kg ore7000--0 20 40Days- 6055.12%614m V 50,- 40o R do Potent al30 U -- e x iII 7% U Recovery J+20+ 1060 800Fig. 8: Change in uranium recovery with Redox Potential at pH1.7 using 80 kg ore300D69.6%T ov2500 702.6x1010 60o >2000 °50 mE 1500 s 40 m f r' Cell CounUmLi £ L-t- Uranium 8io-recovery i° 30 E1000 - 20500 ;---- ---- 00 10 20 30 40 50DaysFig. 9: Change in uranium biorecovery with cell count at pH1.7 using 80 kg oreV,i 10Iif"'"'!"°'R,, ,, f!+!!111111!!!fif"1"II"I1"I1"I"I!!^!111' ^^"191^1111i"PP1"1^P IrkAmenability of Low-grade Uranium towards Column Bioleaching...4. CONCLUSIONSThe low grade uranitite ore of Turamdih mineswasfound to be amenable to bio-leaching incolumn by the native A. ferrooxidans. In 2.5 kglaboratory column, 58.91% uranium bio-recoveryis recorded in 40days at 1.7pH as against-56.82%at 1.9pHn with respective maximum Eh of635mV and 623mV. Control experiments yieldeda lower recovery of 47.91 % in 40days at 1.7pH.On large scale (80kg), bio-recovery of69.80% at' 1.7pH against a control recovery of55.12% in 50 days is achieved with rise in Ehfrom 325 to 638mV and 332 to 614mV. The cell.nts increases from 6.3x107 to 2.66 x 1010cells/mL in 50 days, which aids the oxidation ofiron (Il) and increasing the uranium recovery byindirect mechanism.REFERENCESAbhilash, Singh, S., Mehta, K.D., Kumar, V.,Pandey, B.D. and Pandey, V.M., Microbiallycatalysed process for uranium dissolution from itsore, Int. Sem. Min. Proc. Tech. (MPT-2006),Chennai,2, 717-724 (2006).Colmer A.R. and Hinkle M.E., The role ofmicroorganisms in acid mine drainage: apreliminary report. Science 106,253-256 (1947).349Guay, R., Silver, M. and Troma, A.E., Ferrous ironoxidation and uranium extraction by Thiobacillusferrooxidans, Biotechnol. Bioeng. 19(5), 727-740 (1977).Lizama, H.M. and Suzuki, L, Bacterial leaching of asulphide ore by Thiobacillus ferrooxidans andThiobacillus thiooxidans Part II: column leachingstudies. Hydrometallurgy 22, 301-310 (1989).Mathur, A.K., Viswamohan, K., Mohanty, K. B.,Murthy, V.K. and Seshadrinath, S.T., Technicalnote: Uranium Extraction Using Biogenic FerricSulfate; A Case Study On Quartz Chlorite OreFrom Jaduguda, Singhbhum Thrust Belt (STB),Bihar, India. Min. Eng. 13(5): 575-579 (2000).Muiioz, J.A., Bkizquez, M.L., Ballester, A. andGonzalez, F. 1995. A study of the bioleaching ofa Spanish uranium ore, Part II: Orbital shakerexperiments. Hydromet. 38:59-78.Silverman, M.P. and Lundergren, D.G., Studies ofthe chemolithotrophic iron bacteriumFerrobacillus ferrooxidans. an improved mediumand a harvesting procedure for accuring high cellyields, J.Bacter.77,642-647 (1959).Tuovinen, O.H. and Hsu.C.J. Effect of pH, ironconcentration, and pulp density on thesolubilisation of uranium from ore material inchemical and microbiological acid leachsolutions: Regression equation and confidenceband analysis. Hydromet. 12,141-149 (1984).

Amenability of low- grade uranium towards column

bioleaching by acidithiobacillus ferrooxidans

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Amenability of low- grade uranium towards column bioleaching by acidithiobacillus ferrooxidans

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