Recovery of metal values from spent hydrodesulfurization catalysts by liquid-liquid extraction

The total dissolution of spent hydrodesulfurization catalysts in sulfuric acid yields an acidic solution containing a certain amount of rare metals like molybdenum, vanadium, cobalt, nickel, and a small amount of iron and aluminum. In this paper, for the purpose of recovering the metallic values present in a solution, the basic extraction characteristic of these metals with some typical commercial acidic organophosphorous compounds such as TR-83, PC-88A, PIA-8, and CYANEX 272 from the sulfuric acid media were investigated, and CYANEX 272 and PIA-8 were found to be suitable for selectivity separating and recovering molybdenum and vanadium over the other metals from the specific solution at comparatively low pH. In addition, in order to recover cobalt and nickel from the raffinate in the presence of a large excess aluminum, a systematic investigation was conducted and results showed favorably.