A New Technology Of Extracting Vanadium From The Acid Leaching Solution Of Stone Coal

The composition of the acid leaching solution of stone coal which contains V(â…£), Fe(â…¢), Fe(â…¡) etc is characterized with complexity. Fe(â…¢) is particularly detrimental for the seperation and enrichment of vanadium from the acid leaching solution. The traditional technology of extracting vanadium from the acid leaching solution,reduction for removing Fe(â…¢)â†'solvent extraction of V(â…£)â†'oxidization of the V(â…£) solutionâ†'V(â…¤) precipitating with ammonium saltâ†'ammonium polyvanadate calcination, has realized the mature application in the industry.However, the addition of reducing agent, oxidant and ammonium salt in the process results in not only the rise of the reagent consumption and the cost but also the difficulty of water recycling utilization. On account of disadvantages of traditional process, the present thesis proposed a novel technology, solvent extraction for removing Fe(â…¢)â†'solvent extraction for extracting V(â…£)â†'neutralizing hydrolysis for V(â…£) precipitatingâ†'washing of VO(OH)2for removing Naâ†'VO(OH)2calcination. Using D2EHPA as extractant, a step-by-step solvent extraction of Fe(â…£) remo-val and V(â…£) extraction from the acid leaching solution which contained V2O55.12g/L, Fe3+8.45g/L, Fe2+3.35g/L with pH1.22was studied.With the kerosene solution of15%(v/v) D2EHPA and2%(v/v) TBP,91.48%of Fe(â…¢) was extracted from the solution after5stages counter-current extracting at O/A ratio1:1, contact20min at room temperature. NaCl saturated solution in1.5mol/L HCl was used as the stripping solution.99.21%of the Fe(â…¢) was stripped after5stages counter-current stripping at O/A ratio1:1, contact10min at room temperature. The NaCl saturated solution could be recycled for Fe(â…¢) stripping after neutralization for Fe(â…¢) precipitation-adding HCl-NaCl crystallization. Removing Fe(â…¢) by solvent extraction with D2EHPA was achieved in this process.Using the organic phase used in the process of removing Fe(â…¢) as V(â…£) extractant,near99%V(â…£) was extracted from the removed Fe(â…¢) solution with pH2.3～2.5after7stages counter-current extracting at O/A ratio1:1, contact8min at room temperature.Using1.5mol/L H2SO4as V(â…£) stripping agent, Over99%V(â…£) was stripped after5stages counter-current stripping at O/A ratio6:1, contact15min at room temperature.The vanadium was enriched into the stripping solution which contained28.11g/L V2O5.Eligible concentrated V(â…£) solution was got after the step-by-step solvent extraction from the acid leaching solution.With NaOH as neutralizer, vanadium precipitation percentage reached about99%under the conditions of room temperature, teminal pH5.0～5.5, reaction time over3min. Na could be washed from the precipitation, VO(OH)2, by H2SO4solution with pH≈2.0at ratio of liquid and solid6:1atroom temperature. Vanadium pentoxide with purity over98%and vanadium dioxide were obtained respectively by oxidizing roasting at550℃for2h and calcinating under inert atmosphere at550℃for2h.Compared with the traditional process, thenovel technology got obvious andvantages:Direct extaction for removing Fe(â…¢) which need not reducing agentavoided the procedure of reduction; Stripping with HCl-NaCl saturated solution was quite effective for reducing producted cost and pollution to the environment; V(â…£) precipitation directly from the concentrated V(â…£) solution avoided the procedure ofoxidation. It was conducive to recycling of the wastewater after vanadium extraction due to no addition of oxidant and ammonium salt.Therfore, it is benificial toprotect environmentand could accord with the trend of energy-saving and emission reduction in our country.