Valence State Adjustment for the Recovery of Vanadium and Molybdenum from Spent Residue Hydrogenation Catalysts

ABSTRACT The recovery of valuable vanadium (V) and molybdenum (Mo) from spent residue hydrogenation catalysts is crucial due to their high content. However, their efficient separation from the catalyst leaching solution remains challenging. This study investigates a single-stage extraction and stripping process for V and Mo recovery. Under the optimal conditions with 20 vol% of the extractant Aliquat 336, 10 vol% of the phase modifier n-octanol, and an initial aqueous phase pH of 1.0, V and Mo could be effectively extracted, with a distribution ratio of V being 7.02 and that of Mo greater than 1000. The separation factors of V relative to other impurity elements exceeded 360, while those of Mo with respect to impurity elements were greater than 10,000. Afterwards, selective stripping of V was achieved based on its valence state change using an ascorbic acid (VC)-H2SO4 solution. Mo was subsequently stripped with an NH4HCO3 solution. Applied to an actual leaching solution, this process achieved extraction efficiencies over 99.9% for both metals via a four-stage extraction process, with the co-extraction of impurities below 4.50%. A three-stage stripping with 0.3 mol/L VC–0.5 mol/L H2SO4 yielded V stripping efficiency over 99.9% andminimal Mo costripping efficiency of 1.22%. Subsequently, 99.9% of the retained Mo was recovered using NH4HCO3. Therefore, this study provides an efficient strategy for V and Mo recovery, which has significant practical implications for the sustainable management of spent catalysts.