A literature review of the recovery of molybdenum and vanadium from spent hydrodesulphurisation catalysts: Part II: Separation and purification

Various methods for separation, purification and recovery of molybdenum and vanadium from leach solutions of spent catalysts are reviewed. The main methods include sulphide precipitation, ammonium salt precipitation, carbon absorption, ion exchange and solvent extraction. These methods are briefly compared and assessed for both purification of leach solutions and recovery of molybdenum and vanadium from the solutions in terms of their selectivity, efficiency and product quality. The strategies for recovery of other valuable metals including nickel and cobalt are also reviewed and discussed.Among these methods, precipitation offers low cost and simple operation, however, high purities (> 99%) of products of molybdenum and vanadium cannot be achieved. The loading capacities of activated carbon for molybdenum and vanadium are relatively low, resulting in no industrial application of this technology in the separation of molybdenum and vanadium. Ion exchange offers a useful means for almost complete separation of molybdenum and vanadium and for production of their high purity products, although the scale of application of ion exchange in industry is limited. Solvent extraction is highly selective for separation and recovery of molybdenum and vanadium, and is the most promising method recommended for future research and development.