Source removal of iron and aluminum impurities over vanadium in phosphate-sulfate complex anionic leaching system of the black shale

Abstract

BackgroundThis work aims at achieving the source removal of Fe and Al impurities during the pressure leaching process of black shale, which is beneficial to the subsequent purification and enrichment of V. MethodsPhosphate ions were introduced into the sulfate single anionic leaching system (SSLS) to form the phosphate-sulfate complex anionic leaching system (PSCLS) of the black shale, which enhanced the complexing capability of the leaching system and enabled more of Fe and Al impurities to get transformed into complex precipitates. Significant findingsThe results show that the intervention of phosphate ions reduced the leaching efficiencies of Fe and Al by 82.1% and 47.3%, respectively. Due to the difference in affinity for phosphate and self-hydrolysis capability, Fe and Al impurities were converted into stable precipitates of iron phosphate hydroxide (Fe4(PO4)3(OH)3) and aluminum phosphate (AlPO4), respectively. As a result, Fe and Al impurities leached with V re-enter the slag phase, thus realizing the source removal of Fe and Al impurities.