Extracting vanadium from stone-coal by oxygen pressure acid leaching and solvent extraction

還罗Availableonlineatwww.sciencedirect.comScienceDirectTransactions ofNonferrous MetalsSociety of ChinaELSEVIer PressTrans. Nonferrous Met. Soc. China 20(2010)sl 18-s122Extracting vanadium from stone-coal byoxygen pressure acid leaching and solvent extractionDENG Zhi-gan(邓志敢, WEI Chang(魏昶, FAN Gang(樊刚)LI Min-ting(李旻廷), LI Cun- xiong(李存兄), LI Xing-bin(李兴彬)Faculty of Metallurgical and Energy Engineering, Kunming University of Science and TechnologyKunming 650093, ChinaReceived 6 July 2009; accepted 30 December 2009Abstract: Vanadium extraction from stone-coal was investigated by oxygen pressure acid leaching and solvent extraction. themineralogy of the stone-coal from Tongren City of Guizhou Province, China, was investigated by various determination methodsThe effects of leaching time, leaching temperature, leaching agent concentration, leaching L/S ratio, granularity of material, additiveconsumption were investigated based on the mineralogy. The results show that under the conditions of leaching time of 3-4 h,temperature of 150 C, sulfuric acid consumption of 25%-30%, ratio of liquid to solid of 1. 2: 1, the granularity less than 0.074 mm,additive consumption of 3%-5%, and oxygen pressure of 1. 2 MPa, and the vanadium leaching rate can be more than 92% by themethod of two-step pressurized acid leaching. The powdery ViOs product with 99.52% in V2Os content is obtained by the flowsheetof acid recovery, removing iron by reduction process, solvent extraction, precipitating vanadium with ammonium water, andpyrolysis from the stone-coal oxygen pressure acid-leaching solution. The total recovery efficiency of vanadium is above 85%, whichis more than 20% higher than that obtained in the conventional process. Furthermore, the new process does not cause air pollutionince no HCl or Clz is released by calcination of the raw materialKey words: stone-coal; extracting vanadium; oxygen pressure; acid leaching; acid recovery; solvent extractiondeposition, alkali melting and thermal decomposition1 IntroductionThis classical technology has two main problems, that is,low recovery of vanadium 50%)and seriousVanadium is widely distributed in the nature, but it environment pollution[10-ll]. Serious poisonous gases,is not present alone in mineral deposit of vanadium, and HCl and Cl, are produced in the roasting processit generally occurs in combination with various minerals because sodium chloride is used as an additive, and thethat include carnotite, vanadium-titanium magnetite, wastewater and solid residues contain too highroscoelite, vanadinite, mottramite and patronite as concentration of heavy metals. Increasing environmentalimportant sources of the metal[1-3]. There are two concems and legislation concerning environmentalimportant vanadiumces in China; one is the protection, China banned the application of thisvanadium and titanium magnetite ore, and the other is technology in 2003, thus, the utilization of stone coalstone-coal ore. Stone-coal is carbonaceous shale that was limited[8-10]. Therefore, it is extremely urgent tocontains vanadium[4-8]. In China, the gross reserve of research and develop a new technology with highervanadium in stone-coal is 1.18x10 t in terms of V2Os, recovery of vanadium and no pollution to environmentaccounting for more than 87% of the domestic reserve of for extracting vanadium from stone-coal.[ 9-10]. Conventionally, the extraction ofThe present work focuses on the design of a newvanadium from black shale is performed using the technology on vanadium extraction from stone-coal byclassical technology. The brief fow of the classical oxygen pressure acid leaching and solvent extraction.technology includes chloridizing roasting, water leaching中国煤化工 and develop a newFoundation item: Project(2006AA062130)supported by the High-tech Research andC N MH G874053)supported by theational Natural Science Foundation of China; Project(2007GA0Io suprrespondingauthordeNgZhiganteL+86-871-5188819;Fax:+86-871-5188819E-mail:fed525700@yahoo.comcnDENG Zhi-gan, et al/Trans. Nonferrous Met. Soc. China 20(2010)s118-8312process of extracting vanadium from stone-coal,characterized by higher recovery of vanadium, which wasenvironmentally-friendly2 Experimental2.1 MaterialsStone-coal was collected from Tongren City inGuizhou Province of China. The analytical gradereagents used in this study included sulfuric acid,ferrisulphas, sodium sulfite, di(2-ethy lhexly )phosphoric0686-Roscoe Mte. mou L- KV-SiA-262iCTooacid(P204), tributyl phosphate(TBP), ammonia water,sodium chlorate and sodium hydroxide. All aqueoussolutions were prepared using main-water. The kerosenewas sulfonated with sulfuric acid(AR)to generate Fig. 1 x-ray diffraction pattem of stone-coalsulphonated-kerosene which was employed as diluent ofP204 and tBp2.2 MethodsThe mineralogy of the stone-coal from Tongren Cityof Guizhou Province of China was investigated byarious determination methods, such as scanningelectron microscopy, electron probe analysis, energygravimetric analysis. Based on the mineralogy, theeffects of leaching time, leaching temperature, leaching Fig. 2 SEM image of stone-coal primary mineralagent concentration, leaching L/S ratio, granularity ofmaterial, additive consumption, which were the stone-coal consists of small particles with diameters belowinfluential factors of extraction of vanadium, were 50 um, and vanadium mainly exists in roscoelite, next ininvestigated. The two-step countercurrent acid pressure microcline, and iron oxide and clay mineralleaching with oxygen was carried out. The powderyThe composition of the mineral concentrates used inV2Os product was obtained by the flowsheet of aclis study is listed in Table 1. It can be seen form Tablerecovery from the stone-coal oxygen pressure acid that the content of vanadium in terms of v2Os is 3.26%leaching solution, removing iron by reduction process, (mass fraction, the same below if not mentioned), andsolvent extraction, precipitating vanadium with reaches the industrial treatment gradeammonium water, and pyrolysisVanadium phase and valence state in sample wereanalyzed by electron probe instrument. The results are3 Results and discussionlisted in Table 2. It can be seen from Table 2 that thecontent of vanadium existing in micaceous is 1.471%,3.1 Characterization of raw stone-coalaccounting for 80.55% of total vanadium; the fractionThe X-ray diffraction pattem of stone-coal is shown stacked to iron oxide and clay is 17.98% and the restin Fig. 1. It can be seen from Fig. I that the sample mainly vanadium exists in crystal lattice of insolublemicrocline and silicoaluminate mineral (1.47%)chromceladonite. Fig 2 shows the SEM image of stone-Many researches[ 10-14]indicated that only V.andcoal primary mineral. It can be seen from Fig. 2 that the v*were found in stone-coal generally, and V*and VTable 1 Main chemical components of raw materials(mass fraction, %ViOsNa,OK,OFe?O33.267.6053.0316621.22TFe中国煤化工383.840.00190.0640.700018CNMHGVolatile matter0019000129.09DENG Zhi-gan, et al/Trans. Nonferrous Met. Soc. China 20(2010)s118-s312were barely found. Vanadium in the ore from major concentration, leaching L/S ratio, granularity of material,locality was mostly in the form of V. except for the additive consumption, which were the influential factorsindividual region; meanwhile, V replaces AP* in on extraction of vanadium, were investigated[ 12-14silicoaluminate as the isomorphism form, and V is The results showed that under the conditions of leachingattached to iron oxide and clay mineral. However, as time of 3-4 h, temperature of 150 C, sulfuric acidshown in Table 3, it is inconsistent with results consumption of 25%-30%, ratio of liquid to solid ofmentioned above that the vanadium content in three 1.2: 1, the granularity less than 0.074 mm, P(O2)of 1.2forms(V, v, V)for sample used in this study is MPa and additive consumption of 3%-5%,vanadiumnearly equal and is respectively 0.627%,0.527% and leaching rate was over 92% by the method of two-step0.672%. This indicates that the occurrence condition of reverse flow oxygen pressurized acid leaching. Thevanadium in stone-coal is intricate and inconstantresults of two-step countercurrent leaching are listed inTable 4Table 2 Distribution of vanVanadium phase V content/% Occupation ratio/% Table 4 Results of two-step countercurrent leachingIron oxide032817.98Sample NeLeaching rate of vanadium/%9281Micaceous1.471291.71Insoluble silico-39196aluminate mineral002714792961.826100009199Table 3 Distribution of vanadium at different valencesValenceV content/% Occupation ratio/% 3.3 Preprocess of leachate0.62734.34The methods of extracting vanadium from solution0.527ude oxidation-precipitation[ 15], direct precipitati0.67236.80[16] and solvent extraction[ 17-18]. In this work, thesolvent extraction was performed to extract vanadium inTotal1.826100.00the leachate produced of the two-step countercurrenteaching process, and its composition is presented3.2 Acid pressure leachingTable 5. It can be seen from Table 5 that impurity metalsBased on the mineralogy, to release vanadium(V in solution have a high content because of the poorpresented in mica mineral as the isomorphism form, the selectivity in acidic leaching process. Thisiscrystal lattice of mica must be broken. The reaction is as disadvantageous for the subsequent procedure extractingfollowsvanadium pentoxide from solution [11]V20,X+2H2SO4+1/202-v202(SO4)2+2H20+X (1) 3.3.1 Acid recoveryThe high concentration of sulphuric acid in leachateand the speciation of Vo * is very stable in aqueous would increase the addition of antalkali and ammonia, sosolution. But for vanadium (v presented as the it is very necessary to reprocess this solution beforeabsorption form, the chemical equation is as followsextracting vanadium. Many researches[ 19-21]haveV2O5+H2S04-(VO2)2SO4+H2O(2) successfully recovered sulphuric acid from waste acidVanadium (V+)may present in sample as both solution by diffusion dialyses method; so, the residualsomorphism and absorption, the reaction[ll] issulphuric acid in the solution was recovered by thisethod in this study. The results sheV2O2(OH)4+2H2S04-V2O2(SO4)2+4H2O(3) of sulphuric acid could reach above 85%, the detentionAccording to what has been discussed above, the rate of vanadium and impurity iron are 96% and 95%investigative test was carried out. Then, orthogonal and respectively, and the sulphuric acid concentration in theconditional experiments were designed. The effects of reprocessed solution is about 6.5 g/L. The results of acidleaching time, leaching temperature, leaching agent recove中国煤化工Table 5 Main compositions of leaching solutionsCNMHGComposition V Fe Ca Mg Na K As Si P H,SOaConcentration/(gL4656310.1132620.074037400921.261.67DENG Zhi-gan, et al/ Trans. Nonferrous Met. Soc. China 20(2010)s118-8312s121Table 6 Results of acid recover10%P204, 5% TBP and 85% sulphonated-kerosene TheConcentration of Concentration ofvanadium and iron concentration in the raffinate phaseElementacid(g remnant/(g Lrate/%were 0. 16 g/L and 6.00 g/L, respectively, but they were7.56 g/L and 0.62 g/L, respectively, in the loaded organic9606506300The anti-extraction parameters were as follows:0.0522.560temperature about 45 C, and contact time 15 min. The00140058and 19.35%, respectively, after 5-stage counter-flow anti0.365extraction. The vanadium and iron concentration in00200.070stripped organic phase were 0.065 g/L and 0.50 g/LSi2.02032.150By way of extraction an0.100956stripping solution, the concentration of vanadium couldbe raised to 37 47 g/L or more, and the concentration ofiron can be reduced to 0.6 g/L or less. The mass ratio of3.3.2 Removing iron by reduction proceV to Fe can be up to 62 in aqueous phase of strippingBecause the extractant(P204)employed in thisstudy can coextract vanadium and trivalence iron ion, it and the effects of separation and enrichment are wellwould lead to a low service efficiency of extractant and a 3.5 Precipitation and thermal decompositiongh impurity content. Hence, it iswhichever method (ion exchange resins or solventnecessary to make ferric ion reduced into ferrous ion extraction)was used in separation of vanadium frombefore extracting vanadium[11, 22]. Sodium sulfite was leaching solution, the vanadium was finally precipitatedemployed as the reductant, and the addition was the same as ammonium vanadate by ammonia or ammoniumBecause vanadium in stripping solution was v,theequation coefficient. The reduction rate of ferric ion precipitation of the vanadium from the stripping solutioncould reach 98.2%, Tconsumption on reduction rate of ferric iron is listed in excess of sodium chlorate of concentration 200 g/L wasTable 7added compared with the total amount of vanadium asammonia was added to keep the ph at 2 untiln(Na2SO,VPre-treatment Reduced solution Reducing temperature of solution was heated up to 90 C. Undern(Fe) p(Fe"yofthese conditions, vanadium in stripping solution was(. L") pH ol-1 ph Fe"%gradually crystallized into ammonium vanadate, and th8.521.052.451.2771.26precipitation recovery of vanadium was 99. 2%.After solid liquid separation“ red cake”of0.758.521.051.6583.20ammonium vanadate was thermally decomposited at 5508.521.050.152.319820c for 2 h to produce qualified powder vanadiumpentoxide product with 99.52% in V2O5 content. The3. 4 Solvent extraction and anti-extractioncomposition of powder vanadium pentoxide and productSome parameters of extraction and anti-extraction, quality analyses are shown in Table 8. The overall yielduch as organic phase to aqueous phase(O/A), theosition of solvent, pH and the settingTable 8 Product quality analyses of vanadium peoptimized by a series of tests[22]. The extractionexperiment indicated that the 10% P204, 5% TBP andGB3283-87%Product of test/%85% sulphonated-kerosene system has a good result forVoS≥980099520extracting vanadium. The optimum extracting parameters≤0400.020were organic and water phase ratio(O/A)1: 2, ambientmH中国煤化工0030temperature, the initial pH of water phase 2.3 and contacttime 10 min. Under these conditions, the extracting yieldCNMHG0020of vanadium and iron were 95.94% and 4.91%<0015respectively, after 6-stage counter-flow extraction with≤0.02<0.010DENG Zhi-gan, et al/Trans. Nonferrous Met. Soc. China 20(2010)s118-5312of vanadium recovery could reach about 85%.iron vanadium slag [] Joumal of Beijing University of Chemical4 Conclusionsstudy of a newhnology leaching of vanadium ores with hydrometallurgy []hina Mining Magazine, 2006, 15(7): 64-66.(in Chinese1) Under the conditions of leaching time of 3-4 h, [8] HE Dong-sheng, FENG Qi-ming, ZHANG Guo-fan, OU Le-ming,temperature of 150 C, sulfuric acid consumption ofLU Yi-ping. An environmentally-friendly technology of vanadium25%0-30%, ratio of liquid to solid of 1. 2: 1, thetraction from stone coal [] Minerals Engineering, 2007, 20(12)granularity less than 0.074 mm and additive consumption [9] BIN Zhi-yong. Progress of the research on extraction of vanadiumof 3%-5%, vanadium leaching rate could be more thanpentoxide from stone coal and the market of the ViOs []. Hunan92% by the method of two-step pressNonferrous Metals, 2006, 22(1): 16-20. (in Chineseleaching.10] XIAO Wen-ding. Mineralogy of stone coal from Shanglin of2)After pretreatment of acid recovery, removingGuangxi and vanadium extraction with hydrometallurgical processiron by reduction process and adjusting pH of oxygen[] Nonferrous Metal, 2007, 59(3): 85-90.(in Chinese)pressure acid leached solution, the extraction yield of[11] LU Zhao-ling Investigation and industrial practice on extraction ofV:Os from stone coal containing vanadium by acid process [yvanadium could be up to 92% under the conditions ofhydrometallurgy of China, 2002, 21(4): 175-183(in Chinese)6-stage counter-flow extraction with 10% P204, 5% TBP [12] LI Min-ting, WEI Chang. FAN Gang, DENG Zhi-gan.Theand 85% sulphonated-kerosene, and the strippingpathbreaking experimentation study on extracting vanadium fromefficiency of vanadium would exceed 99% when 15%stone-coal by acid leaching with oxygen pressure [J]. ChineseJoumal of Rare Metals, 2007, 31 (s): 28-31.(in Chinese)Hn SOA solution is taken as the stripping agent. By way of [13] WEI Chang, FAN Gang LI Min -ting, DENG Zhi-gan. Study on mainextraction, the concentration of vanadium could be raisedfactors effect of extracting vanadium from stone coal containingto 37 g/L or more, and the concentration of iron could bevanadium by acid leaching with oxygen pressure [] Chinese Joumalreduced to 0.6g/L or less. The mass ratio of v to Feof Rare Metals, 2007, 31(s):98-101. (in Chinesecould be up to 60 in aqueous phase of stripping, and the [14] DENG Zhi-gan, LI Cun-xiong. WEI Chang. LI Min-ting, LIANGeffect of separation is goodan-hui, WU Hui-ling. Research on new process ofextraction from vanadium containing stone coal by acid3)By this technology, vanadium could be recoveredder oxygen pressure []. Metal Mine, 2008(7): 30-33.(infrom stone-coal with recovery of 85% in the whole [15] VITOLO S, SEGGIANI M. Recovery of vanadium from heavy oilprocess, which prevents air pollution since noand Orimulsion fly ashes[]. Hydrometallurgy, 2000, 57: 141-149is released by calcination of the raw material[16] LOZANO L J, JUAN D. Solvent extraction of polyvanadates from4)By this technology, the purity of the productlphate solutions by Primene 8IR: Its application to the recovery ofvanadium from spent sulphuric acid catalysts leaching solutions p]anadium pentoxide reaches 99.52%, which is up to theSolvent Extract and lon Exchange, 2001, 19(4): 659-676mustard quality of GB3283--87 of China[I7 ZHANG P W, INOUE K, YOSHIZUKA K, TSUYAMA H.5)The advantages of this process are: short route,traction and selective stripping of molybdenum (Vi)andsimple operation, high coefficient of recovery and betterV) from sulfuric acid solution containing aluminum(lIf), cobalt(u).economic efficiency, society benefits and environmentnickel (In) and iron (lll) by LLX63 in Exxsol D80 U)hydrometallurgy, 1996, 41: 45-53acceptability[18 BAL Y, BAL K E, GOTE Gi LALLAMC A. 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