Green Process Of Vanadium Leaching From Low-grade Vanadium-containing Stone Coal

Vanadium is an important strategic material and has excellent physical andchemical properties, and has found wide applications in steel industry, chemicalindustry and medicine industry. The reserves amount of V2O5in stone coal accountsfor major of the total vanadium reserves. The full use of the stone coal reserves shouldbeen developed with the vanadium conduct growing consumer market. The traditionalprocess cause serious environmental pollution and low efficiency. Therefore, it haspositive significance to search a new vanadium leaching process from stone coal fordeveloping the stone coal reserves, which is highly efficient and environment friendly.The vanadium-containing stone coal collected from Wuxi Country, Chongqing City,and the representative samples of stone coal gangue(SCG) and vanadium–containingstone coal (VSC) were selected as study subject. Experiments focused on the vanadiumrecovery from roasted residue by calcified roasting technology to avoid environmentalpollution and improve vanadium leaching ratio.SCG sample was pretreated by calcified roasting-acid leaching technology, andcalcium oxide was used as additive. By single-factor experiments and orthogonalexperiments, the effect of roasting temperature on vanadium leaching ratio was first,then the roasting time, concentration of sulfuric and leaching time. The propertechnological conditions of calcified roasting-acid leaching technology were followingas,950℃of roasting temperatures,4h of the roasting time,40%of sulfuric solutionand6h of leaching time. Under the proper condition, the leaching ratio of vanadium inSCG was85.48%.VSC sample was pretreated by calcified roasting-sodium chlorate acid leachingtechnology. In the process of calcified roasting, effect of roasting temperature on thevanadium leaching ratio was first, and then CaO dosage and roasting time. During theprocess of sodium chlorate-acid leaching, the order on influence factors for leachingratio is following as, additive amount of sodium chlorate＞liquid-solid ratio＞leaching time＞concentration of sulfuric. The proper technological conditions ofcalcified roasting-sodium chlorate acid leaching technology were following. The CaOdosage was45%, roasting temperature is950℃,roasting time was4h, addition ofsodium chlorate was16%, liquid-solid ratio was16%, leaching time was4h and concentration of sulfuric was30%. The leaching ratio of vanadium in VSC was98.45%under the above conditions.The vanadium separation and purification were done by extraction-stripping-ammonium salt technology. In the extraction process,10%P204-5%TBP-85%sulfonated kerosene was used as extraction system. The proper conditions of extractionsystem through single stage extraction experiment were following. The pH of raffinateis2.3±0.05, O/A ratio is1/1, oscillation time is10minutes. The extraction ratio canreach to79%. The separatory funnels were selected to simulate multi-stagecountercurrent extraction process. After calculation, the countercurrent multi-stageextraction stage was5. The sulfuric acid was taken as stripping agent in the strippingprocess. The proper stripping conditions were following. The concentration of sulfuricwas1.5mol/L, O/A was1/1, oscillation time was12minutes. After3stage ofcountercurrent multi-stage stripping, the vanadium in organic phase transferred to theaqueous phase, and the solution was blue.The red ammonium ployvanadate can be directly precipitated through addingammonium chloride. After the precipitation was filtered, washed many times, dried,and then calcined in the muffle furnace at550℃for2h, the product of V2O5was gotten.The purity of V2O5was98.92%. The product of V2O5can reach national standard forvanadium pentoxide V2O598(GB3283-87).