Integrated Hydrometallurgical Recovery of Vanadium from Spent Petrochemical Catalysts for the Production of High-Purity Ammonium Metavanadate

An integrated hydrometallurgical process for the recovery of vanadium from spent petrochemical catalysts and the production of high-purity ammonium metavanadate (AMV) was developed and experimentally validated. Alkaline leaching of roasted vanadium-bearing catalysts resulted in vanadium extraction of 90%–95%, producing a solution containing 37.0 g/L V2O5 together with phosphorus, sulfur, silicon, and molybdenum impurities. Two purification approaches, ion-exchange sorption and magnesium oxide treatment, were evaluated for impurity removal. Sorption using the macro porous anion-exchange resin Biolite 200U provided effective silicon removal but resulted in significant vanadium losses (up to 19.6%) due to co-sorption of vanadium and phosphorus. In contrast, magnesium oxide treatment at 70–80 °C reduced the phosphorus concentration from 0.39 to 0.04 g/L (approximately 90% removal) and completely removed silicon while limiting vanadium losses to less than 2.5%. Following purification, ammonium metavanadate was precipitated using ammonium chloride at a V2O5:NH4Cl molar ratio of 1:2 and pH 8.8–9.0, achieving approximately 99% vanadium recovery. X-ray diffraction analysis confirmed the formation of single-phase NH4VO3 after solution purification, whereas precipitation from untreated solutions resulted in contamination by alumina-bearing phases. The proposed process provides an effective route for producing purified ammonium metavanadate suitable for subsequent conversion into metallurgical-grade V2O5. The ultimate goal of the proposed technology is the production of metallurgical-grade ferrovanadium (FeV80). Because AMV is thermally converted to V2O5 with a weight loss of approximately 24%–25%, phosphorus and sulfur concentrations in AMV must be maintained below approximately 0.04 wt.% to ensure compliance with the impurity requirements of FeV80 according to GOST 27130-94.