Recovery of molybdenum and vanadium from synthetic sulphuric acid leach solutions of spent hydrodesulphurisation catalysts using solvent extraction

A commercially available extractant, LIX®63 was used to investigate the extraction of molybdenum(VI) and vanadium(V) from a synthetic sulphuric acid leach solution of spent hydrodesulphurisation catalysts. The molybdenum(VI) and vanadium(V) were extracted and separated completely from other metals at pH 1.5. The loaded organic solution was easily stripped by NaOH solution with excellent phase separation. After the precipitation of most of the vanadium(V) as ammonium vanadate from the loaded strip liquor, a pure molybdate solution could be obtained by further removing the small amount of vanadium(V) remaining in the filtrate using Aliquat 336 at pH 8.5. Therefore, both pure molybdenum(VI) and vanadium(V) products can be obtained. The separation of nickel(II) and cobalt(II) from iron(III) and aluminium(III) in the raffinate after the recovery of molybdenum(VI) and vanadium(V) could be achieved by ion exchange with Dowex M4195 resin. A process flowsheet has been developed to recover the valuable metals from leach solutions of spent hydrodesulphurisation catalysts.