International Journal of Minerals, Metallurgy and MaterialsVolume 17, Number 4, August 2010, Page 381DOI: 10.1007/s12613-010-0330-8A new process of extracting vanadium from stone coalYan-hua Liul?2), Chao Yang", Pei-you Li2), and Shi-qi Li)1) Mallurgical and Ecologial Engineering School, University of Science and Technology Bejing, Bejing 10083, China2) Beiing Nengtai Environmental Protection Group Corp, Beijing 10022, China(Received: 1 July 2009; revised: 22 July 2009; acepted: 10 August 2009)China was introduced. Various leaching experiments were carried out, and the results show that the vanadium ore in Fangshankou is difficultto process due to its high consumption of acid and the high leaching rate of impurities. However, the leaching rate can be up to 80% and thecontent of V2Os in the residue can be between 0.22%-0.25% in the process of ore fine grinding- →oxidation roasting-→mixing and ripen-ing- >aquecous leaching- >P2O4 solvent extraction- >sulfuric acid stripping- >oxidation and precipitation- >decomposition by heat. Also, thequality of flaky V2Os produced by this process can meet the requirements of GB3283- 87. The total leaching rate of vanadium is 70%. Also,three types of wastes are easy to treat. The vanadium extraction process is better in relation to the aspect of environmental protection than thesodium method.Keywords: stone coal; vanadium; extraction; leaching; solvent extraction; V2Os1. Introductionsolvent extraction; for ion exchange, it is diffcult to finda resin with a large loading capacity of V currently. TheStone coal is one of the important mineral resources con-process of oxidation roasting- →acid leaching- →purificationtaining vanadium. In China, the gross reserve of vanadium→precipitation is only developed for stone coal with V+ [7],in the form of V2Os in stone coal is 118 million tons, ac-but the vanadium existing in the stone coal from Dunhuangcounting for more than 87% of the domestic reserve of va-area (Gansu Province, China) is V"t. Therefore, these threenadium [1]. In the 1970s, some companies began to extractprocesses are not suitable for the stone coal from Fang-vanadium from stone coal using the conventional technol-shankou of Dunhuang. However, the reserves of this kind ofogy. The brief flow sheet of the conventional technology in-coal stone in Gansu Province are large enough to explorecludes chloride roasting, leaching, deposition, alkali melting,and utilize. The aim of this paper is to seek an efficientand thermal decomposition [2]. This process is costly andtechnology of extracting vanadium from this kind of stonecomplicated with a low recovery of vanadium [3]. Moreover,coal in Gansu Province.it causes serious environmental pollution with poisonous2. Materials and methodsgases and waste water [4].A large amount of research work has been conducted to2.1. Materialsimprove the conventional process of recovering vanadiumRaw stone coal used in this study was taken from Fang-from stone coal. Some new processes, such as hypohalineshankou of Dunhuang, Gansu Province in China. Afterroasting-→acid leaching- >solvent extraction, roasting with-crushing and grinding, the particle size of the stone coal wasout chloride- →acid leaching- →ion exchange, and oxidationreduced to -100 and -60 mesh, respectively. The main min-roasting-→acid leaching- >purification- →precipitation, havecrals in the ore were quartz, roscoelite, dravite, calcite, andbeen studied [5-8]. The formation of a third phase ancarbon.' The chemical composition of the mineral samples isthe unstable operation limit the industrial application ofshown in Table 1.Corresponding author: Shi-qi Li E-mail: lshiqiustb.du.cn.◎University of Science and Technology Bejing and Springer-Verlag Berlin Heidelberg 2010中國煤化工包SpringerMYHCNM HG382Int J. Miner. Metall. Mater, Vol.17, No.4, Aug 2010Table 1. Chemical composition of mineral sampleswt%Size 1 meshSiO2Al2O3Fe2O3K2OMgOTiO2CaO-600.7864.38.83.32.80.700.570.230.16-1000.7161.6_8..4.60.630.510.200.15Size / meshNa2OBaOSrOCr2O3ClZnO2MoO3_AsZnO_C0.350.120.040.030.020.0116.50.240.130.100.03 .21.5The following chemical agents were used in the experi-Raw stone coalments: D2EHPA (>93vol%); industrial grade sulfonatedCrushing and grindingkerosene; 98vol% H2SO; chemically pure ammonia, so-dium sulfite, sodium chlorate, hydrochloric acid, and cal-cium oxide.| RoastingRoastingMixing acid2.2. Experimental proceduresand ripening || Mixing and leachingand ripeningThe raw coal was crushed and ground, then, three kindsAqueous leachingof leaching processes were selected in the experiments:grounding, mixing and leaching; mixing acid, ripening, andaqueous leaching; and roasting, mixing acid and ripening.ReducingAfter leaching, vanadium in the leaching liquor was reducedExtractionto V+ by reduction treatment, then, the leaching liquor wasenriched and purified by extraction and stripping, and get[Strippingthe high-purity vanadium solution. Finally vanadium wasPrecipitating V by acidprecipitated from the high-purity vanadium solution by acidammonium saltammonium salt, and flaky V2Os was obtained by pyrolysis.PyrolysisFig. 1 is the flow sheet of vanadium extraction from stonecoal.Flaky V2O,Fig. 1. Flow sheet of vanadium extraction from stone coal.3. Leaching vanadium from ores3.1. Grinding, mixing, and leachingmore efficient technologies to improve the leaching processfor the vanadium-bearing stone coal ore.The ore was ground to -100 and -60 mesh respectively,and then the raw ore and roasted ore were mixed and3.2. Mixing with acid, ripening, and aqueous leachingleached separately using the conventional technology. ThAccording to Ref. [9], higher temperature, higher acidity,experimental results are shown in Table 2.and longer reaction time are needed in the process of leach-As shown in Table 2, under conventional leaching condi-ing V from stone coal. Therefore, the tests of ripening andtions, the leaching rate of the raw ore and the roasted oreleaching under the conditions of mixing with acid and heat-will not exceed 25%. Therefore, it is necessary to search foring were conducted to examine the effects of the particle sizeTable 2. Experimental results of mixing-leaching_OLeaching conditionLeachingNo.Mass/g Size I mesh_ V2Os content 1 w%PretreatmentAcid/gT'CTime / hrate/%1000)0216.120030616.3550°C, roasting4h22.0-6中國煤化工13.8550°C, roasting4 h .18.9TYHCNMHG-Y.H. Liu et al, A new process of extracting vanadium from stone coal383of the ore and the acid amount on leaching rate. The ex-Table 3. Experimental results of mixing with acid, ripening,perimental results are shown in Table 3. It shows that theand aqueous leachingleaching rate of V increases sharply after mixing with acidOre*Leachingand ripening. The acid amount affects the leaching rateMass/ Size/ V2Os con- Acid/grate/ %meshtent. / wt%markedly. Whereas the particle size of the ore has lttle ef-00-10C0.712051.2fect on leaching rate. When the acid amount is 30 g, the-1002567.8leaching rate is 70%.100074.33.3. Roasting, acid curing, and ripening3073.5-600.7854.1To further enhance the leaching rate and to reduce the5065.0consumption of sulfuric acid, the ore was roasted first, and70.0then mixed the roasted ore with acid. The experimental re-6070.5sults are listed in Tables 4 and 5.* Ripening condition: 120°C, 24 h.Table 4. Experimental results of powder oxidation and roastingOreRoasting conditionCalcine- Average ignitionMass/ V2Os content / Temperature 1V2Os content/Size / meshTime/hMass/gloss /%___Cmixing 1 30 min_wt%1483.30.9325504130.94-683020016800.92578.80.92392.50.91000784.00.901580.0Table 5. Experimental results of mixing with acid, ripening, and leaching after roastingRoasted oreLeaching residueLeaching rate 1%Acid/gSize/mesh Mass/g V2Os content/ wt%V2Os content/ wt%_ LiquidResidue2(83.40.58947.947.22:83.10.42863.761.83(83.00.23287.79.382.20.57649.682.00.42065.762.2_3(80.50.220_84.6).5*Ripening condition: 120C, 48 h.As shown in Tables 4 and 5, roasting causes the ignitionleaching. The best leaching conditions are listed as follows:loss of 16%-21%, thus, the vanadium grade increases toacid amount, 30 g; ripening temperature, 120-150°C; ripen-0.91wt%-0.93wt%. When the calcine was mixed with aciding time, 48 h; the particle size of the ore sample, -60 orand leached, the leaching rate increases with the increase of- 100 mesh; and during the process of leaching with cleanthe acid amount. And the max leaching rate can reach aboutwater at room temperature, the ratio of liquid to solid80%. However, the roasting procedure may raise the energy(L/S)=1.5/2.0 and the leaching time is 1 h. The residue isconsumption and labor cost.washed, and the liquid goes back to the leaching process andTo sum up, the leaching rate can be increased up to morethe solid can be used as the buildling material after lime neu-tralization.than 80% and the content of V2Os in the residue can be0.22wt% by using the new leaching process: grind-The chemica中國煤化工hing liquor ising→oxidation roasting- →mixing and ripening -→aqueousshown in TablefYHCNMHG384Int J. Miner. Metall. Mater, Vol.17, No.4, Aug 2010Table 6. Chemical composition of leaching liquorg:LSize/mesh V2O3_ EFeFe2AL_ SiO2__CaMgHPotential / mVRemarks-602.14 10.47 1.479.76 0.106 1.01 0.292 0.008 64-462Raw ore-1003.36 11.75 <0.005 10.9 0.130 0.96 0.310 0.009 5:Oxidation-roasting oreAs shown in Table 6, when the raw ore is ground, mixedreductant and calcium oxide as the neutralizer. The electricwith acid and leached, the electric potential of the leachingpotential of the solution should be maintained at aboutliquor is -462 mV, ZFeis 10.47 g/L, Fe+ is 1.47 g/L; when-200-- 240 mV and the pH value at 2.5-2.8. The experi-the oxidation-roasting ore is ground, mixed with acid andmental results are shown in Table 7.leached, the potential of the leaching liquor is- -670 mV,As shown in Table 7, the loss of vanadium can be lessEFe is 11.75 g/L, Fe2t is less than 0.005 g/L, and almost allthan 1.0% when CaCO3 was used as the neutralizer and ironof the ions in the leaching solution are Fe'+. Therefore, thepowder as the reductant. Because of the higher amount ofconsumption of the reductant will be increased when the oreFet+ in leaching solution II, the Fe consumption is higher.is leached after oxidation-roasting.4.2. Extraction of vanadium4. Extraction and stripping4.2.1. Effect of the pH value of equilibrium aqueous phaseon the extraction rateIn the leaching liquor, besides vanadium, there are alsoplenty of impurities that need to be separated. The methodsThe extractant consisted of 10wt% P2O4, 5wt% tributylof extracting vanadium from a solution include oxida-phosphate (TBP), and 85wt% sulphonated kerosene. Extrac-tion-precipitation [10], direct precipitation [1 1], and solventtion juice II was selected to carry out the experiment in aextraction [12-13]. Many studies have been devoted to re-tube-type separating funnel with a volume of 100 mL. Thecovering vanadium from an aqueous solution by solvent ex-experimental conditions were: room temperature (20-25°C);traction with organic solutions of various extractants [14-16].organic/aqueous (O/A)= 1/1; mixing time in the oscillator,Solvent extraction, as an efficient way to separate and purify,10 min. The pH value of the aqueous phase at equilibriumhas several advantages, such as good selectivity and separa-and the concentration of vanadium were measured, and thetion efficiency, high recovery rate, low cost, continuous op-extraction rate was calculated. The experimental results areeration, and easy for automatic control. In this study, sulfu-shown in Fig. 2.ric acid was used to extract vanadium from the solution.Fig.2 shows that the extraction rate of V goes up with the4.1. Pretreatment of extraction solutionincrease in the pH value of equilibrium aqueous phase. It isP2O4 is more efficient for extracting V+t than extractingnecessary to neutralize H released during the process of ex-Vst, but there are a few Vs+ produced due to the oxidationtraction. However, if the pH value is too high (>3.0), ironby concentrated sulfuric acid. Therefore, pre reductionand aluminum in the aqueous will precipitate by hydrolysis,should be carried out before extraction. Reductant (sodiumwhich will prevent the two phases from separating. There-fore, the pH value of equilibrium aqueous phase should besulfite or scrap iron) should be used to reduce V>+ to V++ andmaintained at 2.5-2.8.Fe3+ to Fe2*. In this study, the iron powder was used as theTable 7. Preliminary experimental results of the extraction solutiongL1Potential /Fe-Consu- CaCO3 Con-SolutionV2Os EFe Fe+ ASiO2C:mVmption_sumptionLeaching2.14 10.47 1.47 9.76 0.292 0.106 1.0164-462 .Un- solution Itreated Leaching3.3611.75 <0.005 10.90 0.310 0.130 0.965:-670solution IIExtraction4.664.82.13 14.83 14.64 7.80 0. 2900.100 0.77 pH 2.73-234Treatedjuice I(solution)5.8860.5juice II3.34 16.75 16.60 7.20 0.300 0.110 0.70中國煤化工) (olutio)Note: extraction juice I in total, 46.7 L; extraction juice I in total, 13 L."THCNMHGY.H. Liu et al, A new process of extracting vanadium from stone coal3851004.2.2. Effect of the contact time between two phases on the95extraction rate of vanadium9The experimental conditions were: the composition of the85extraction juice, as shown in Table 8; O/A=1/1; room tem-80perature (28-35°C). The experiment was carried out in thetube-type separating funnel and the two phases were mixed75by a Kang Clan oscillator. The experimental results are70listed in Table 8.囂65As shown in Table 8, the longer the contact time of the6(1.02.0 2.53.03.5two phases, the higher the extraction rate of vanadium.HHowever, when the contact time exceeds 10 min, the extrac-Fig. 2. Effect of the pH value of equilibrium aqueous phasetion rate of Fe' + increases sharply. Therefore, the appropri-on the extraction rate of vanadium.ate contact time for the two phases is 10 min.Table 8. Dynamics of vanadium extraction by 10wt% P2O4V2Os concentration inEquilibrium aqueous phaseExtraction rate of Extraction rate ofContact time / minequilibrium organicV/%Fe/%V2Os concentration/(gLl)phase/ (g:L5)2.18.242.62.94.62.150.942.471.86.52.100.782.5676.60.732.6178.110.102.050.652.6980.52.00. 622.7281.48.3160.592.7582.325.74.2.3. Determination of the vanadium saturation capacityting O/A=1/2, the theoretical extraction stages are 5.Cross-current extraction was used to determine the vana-4.2.5. Verification experiment of the six- stage countercur-dium saturation capacity when the organic phase (10wt%rent extractionP2O4+5wt% TBP+85wt% sulphonated kerosene) was usedTo verify the determined 5-stage extraction, a six-stageas the extractant. Extraction juice II was used as the extrac-countercurrent extraction experiment was carried out. Thetion juice. The other experimental conditions were: contactexperimental results are shown in Table 10.time, 10 min/time; phase-formed time, 30 min; O/A=1/2.The experimental results are shown in Table 9. It shows thatTable 9. Experimental results of vanadium saturation capac-the vanadium saturation capacity is 7.20 g/L under the ex-perimental conditions.Eqilibrium aqueous phase V2Os concentration4.2.4. Determination of the stage of vanadium extractionContactin equilibriumV2Os concentration/timespHorganic phase /To determine the stages of vanadium extraction, th(gLh)(gL)_value of O/A in the experiment was changed. The experi-1.04.4.60mental conditions were: extraction juce, extraction juice II;2.685.92contacting time, 10 min; room temperature (28 30°C).2.203.046.53After the multi-stage countercurrent extraction of vana-3.136.95dium, an extraction rate of vanadium greater than 99% is3.227.20required and the concentration of vanadium in raffinate中國煤化工7.20phase should be less than 0.03 g/L. According to Fig. 3, set-YHCNM HG386Int J. Miner. Metall. Mater, Vol.17, No.4, Aug 2010the stripping solution by using the former one and ammo-nium vanadate by using the latter one. Considering the con-sumption of the reagents, the wasted water and the exhaust,sulfuric acid solution was selected as the stripping agent.5F24.3.1. Effect of sulfuric acid concentration on vanadiumstripping2t/3O/A=1/2The experimental results of the effect of sulfuric acidconcentration on vanadium stripping are shown in Table 11. .The experiment conditions were: vanadium concentration in1.522.533.54Vanadium concentration in equilibriumthe equilibrium organic phase, 6.65 g/L; O/A=5/1; roomaqueous phase/(gL")temperature.Fig. 3. McCabe-Thiele diagram of vanadium extraction byAs shown in Table 11, with the increase in the concentra-10wt% P2O4tion of sulfuric acid, the vanadium stripping rate increases,but the residual acid also increases. When the concentrationTable 10.of sulfuric acid reaches 1.5 mol/L, the residual sulfuric acidtraction simulationreaches 1.04 mol/L. With the continuous increase of theEquilibrium aqueous phaseconcentration, the stripping rate increases slowly, while theStage equilibrium organicPHV2O3 concentration/residual acid increases sharply. To reduce the consumptionphase/(g:L)_(gL)16.6502.101.080of both acid and ammonia, the concentration of sulfuric acid2.1301.950.42(was determined as 1.5 mol/L.0.8201.900.2404.3.2. Effect of contact time on the stripping rate of vana-0.4801.860.071dium0.122 ;.810.0170.0141.78<0.010The experiment conditions were: vanadium concentrationin the equilibrium organic phase, 6.65 g/L; concentration ofAs shown in Table 10, at the fifth stage, the concentrationsulfuric acid, 1.5 mol/L; O/A=1/1; room temperature. Theof vanadium in raffinate phase is 0.017 g/L and the extrac-experimental results are shown in Table 12.tion rate of vanadium is 99.5%. The results indicate that theAs shown in Table 12, sulfuric acid solution can stripdetermined stage of extraction is proper.vanadium effectively, but the stripping rate is slow. At the4.3. Stripping of vanadiumexperimental conditions, the longer the stripping time, theSulfuric acid solution and dilute alkali solution can behigher the stripping rate, but also the higher the cost on bothused to strip vanadium from P2O4 containing vanadium.the utility of equipment and consumption of extractants. TheAmmonium polyvanadate and red cake can be made frombest stripping time is set at 15 min.Table 11. Effect of sulfuric acid concentration on the stripping rate of vanadiumConcentration of sulfuricV2Os concentration in equilibrium Stripping rateH+ concentration/V2Os concentration /acid/ (molL-)organic phase/(gL)1%(mol:L)0.100.072.436.167.40.500.3910.24.6130.71.010.7324.51.7573.71.50.0428.90.8786.82.001.6730.10.6390.562.492.1630.8中國煤化工MYHCNMHGY.H. Liu et al, A new process of extracting vanadium from stone coal387Table 12. Effect of contact time on the stripping rate of vanadiumMixing time /Equilibrium aqueous phaseV2Os concentration inStageequilibrium organicStripping rate/%minHt concentation/ (molL ') V2Os concentration/(g:L)phase /(gL)151.473.682.9755.321(1.454.901.7573.71:1.435.411.2481.4205.740.9186.32:5.770.8886.85.780.876.94.3.3. Definition of the stage of strippingphase reaches as low as 0.046 g/L and the stripping rate isgreater than 99%. The experimental results prove that the150-g/L sulfuric acid was used as the stripping agent; the4-stage stripping is proper.organic phase contained 6.65 g/L V2O;; the contact timewas set at 15 min. At room temperature, the experiment wascarried out by changing O/A and the backwash isotherm was35上drawn. The experimental results are shown in Fig. 4.Setting O/A=5/1, the organic phase containing vanadium0.05 g/L, and the lean organic phase containing no V2Os, we言20can draw the operating line from which it can be seen that atthe 4-stage stripping the stripping rate is over 99.0%.15上4.3.4. Verification experiment of the six-stage countercur-10 trent strippingO/A-S/1To verify the 4-stage stripping test, a six-stage counter-0 0.20.40.60.811.21.41.61.82current stripping experiment was carried out. The results areVanadium concentration in equilibrianshown in Table 13.organic phase/(g:L)As shown in Table 13, under the experimental conditions,Fig. 4. McCabe-Thiele diagram of vanadium stripping fromat the fourth stage, the concentration of vanadium in organic10wt% P2O4 by sulfuric acid.Table 13. Experimental results of 6-stage countercurrent stripping simulationV2Os concentration in equilibriurm organicH+ concentration/ (mol:L l)V2Os concentration/(g.L-)phase/(g:Lh)1.1633.2001.1001.445.4400.2131.481.0001.510.4101.520.1650.0201.530.0350.0125. Preparation of V2Os productThis method has been widely used in plants producinghigh purity vanadium with a high recovery of metal deposi-5.1. Precipitate vanadium from ammonium salttion, less water content in sediments, and less consumptionThere are four methods to prepare vanadate from purifiedof ammonium salt and acid.vanadium solution [2]: hydrolysis precipitation, precipitateThe pure liquid obtained from the experiment is acidicV from acid ammonium salt, precipitate V from weak acidvanadic sulfate (VOSO4), in which vanadium is tetravalent.ammonium salt, and precipitate V from weak alkaline am-The tetravalent中國煤化工before deposit-monium salt. In this study the second method was adopted.ing. Ammoniumte was used asYHCNM H G"388Int J. Miner. Metall. Mater, Vol.17, No.4, Aug 2010the oxidant with the concentration of 150-200 g/L. The re-Referencesaction was carried out at 60-65°C strring for 1-1.5 h with an1] Z.Y. Bin, Progress of the research on extraction of vanadiumoxidation-reduction potential of- 900 mV.pentoxide from stone coal and the market of the V2Os, HunanThe concentration of acid is generally 1.0-1.1 mol/L inNonferrous Met, 22(2006), No.1, p.16.vanadium solution because of the sulfuric acid used in the[2] M.J. Qi, The status and prospects of vanadium leaching fromstone coal, Hydrometall. China, 72(1999), No.4, p.1.process of stripping. Therefore, when adding concentrated3] C.Y. Luo, The study of new process on the extraction of Va-ammonia solution into vanadium solution, ammonium sul-nadium from stone coal, Hunan Nonferrous Met, 1995, No.4,fate will be precipitated, and additional ammonium salt is .not needed as long as n(V5t)/n(NH)= 1/0.33 and the pH4] W.C, Dai, QJ. Zhu. Q.B. 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Cai, Development of vanadium extraction from stonewas decomposed by heating for 2-3 h at 700°C, and flakycoal in Hunan Province, Rare Met. Hard Alloy, 2001, No.l,V2Os can be obtained after natural cooling. Its quality meets[8] J.Q. Cai, The new process of production of vanadium fromthe requirements of GB3283- -87.stone coal, Inorg. Salt Ind, 2001, No.5, p39.In the process, the leaching rate is 80%, the extraction9] Z.L. Lu, Investigation and industrial practice on extract ion ofV2Os from stone coal containing vanadium by acid process,rate of vanadium is 99.5%, the stripping rate is 99%, theHydrometall.China, 21(2002), No.4, p.175.deposition rate of vanadium is more than 99%, the decom-[10] S. Vitolo and M. Seggiani, Recovery of vanadium fromposed rate of vanadium is 97%, and if the rate of crushingheavy oil and Qrimulsion fly ashes, Hydrometallurgy,and roasting is about 96%, the total recovery of vanadium in57(2000), No.2, p.141.the whole process is over 70%.[1] LJ. Lozano and D. Juan, Leaching of vanadium from spentsulphuric acid catalysts, Miner. Eng., 14(2001), No.5, p.543.6. Conclusions[12] M.A. Olazabal, M.M. Fernandez, LA. Madariaga, and J.M.Madariaga, Selective extraction of vanadium (V) from solu-(1) The leaching rate can be up to 75%-80% and thetion containing molybdenum (VI) by ammonium salts dis-amount of V2Os in the residue can be 0.22%-0.25% in thesolved in toluene, Solvent Extr. lon Exch., 10(1992), p.623.process of crushing and grinding- →oxidation roasting- →[13] P.W. Zhang, K. Inoue, K. Yoshizuka, and H. Tsuyama, Ex-traction and selective stripping of molybdenum (VI) and va-mixing and ripening-→aqueous leaching.nadium (V) from sulfuric acid solution containing aluminum(2) Solvent extraction and stripping is an efficient way to(II), cobalt (I), nickel (I) and iron (II) by LIX63 in Exxsolseparate and purify a leaching solution containing vana-D80, Hydrometallurgy, 41(1996), p.45.dium.[14] LJ. Lozano and D. Juan, Solvent extraction of polyvanadatesfrom sulphate solutions by Primene 81R. Its application to the(3) The process of ore fine grinding- →oxidation roast-→recovery of vanadium from spent sulphuric acid catalystsmixing and ripening -→aqueous leaching-→P2O4 solvent ex-leaching solutions, Solvent Extr. lon Exch, 19(2001), No.4,p.659.traction- >sulfuric acid stripping- >oxidation and precipita-tion- >decomposition by heat can effectively extract vana-of pure vanadium pentoxide from spent catalyst by solventdium from the stone coal of Fangshankou of Dunhuang, andextraction, Trans. Indian Inst. Met, 49(1996), No.6, p.795.the total recovery of vanadium in the whole process is over[16] P. Nekovar, D. Schrettrova, and M. Mmka, Extraction of70%. The metallurgical quality of flaky V2Os obtained canmetal ions with a primary amine, J. Radioanal. Nucl. Chem,meet the requirements of GB3283- -87.223(1997), ;中國煤化工TYHCNMH G