A review of metallurgical processes and purification techniques for recovering Mo, V, Ni, Co, Al from spent catalysts

With the continuous development of industrialization and the depletion of ore resources, the recovery of valuable metals from spent catalysts has attracted the attention of researchers. Generally, the spent catalyst contains many valuable metals, which can be used as a secondary resource to replace ore. In this paper, several metallurgical processes for recovering spent catalysts are introduced. There are currently three methods of recovering valuable metals from spent catalysts: hydrometallurgy, pyrometallurgy, and pyro-hydrometallurgy. Of the three methods, pyro-hydrometallurgy seems to be the best choice. It makes up for the shortcomings of both pyrometallurgy and hydrometallurgy. It retains the selectivity of pyrometallurgy to metals such as nickel and iron. It can be well dissolved in the leaching solution, reducing subsequent processing difficulty. Moreover, it can be well dissolved in the leachate so that the difficulty of subsequent processing can be reduced. The leached valuable metals need to be separated and purified to obtain products that meet the process requirements. The main purification techniques for recovering valuable metals from leachate include chemical precipitation, ion exchange, carbon adsorption, and solvent extraction. Among them, solvent extraction is a separation and purification technology worthy of admiration. Solvent extraction has the characteristics of high recovery metal purity, high selectivity, accessible and continuous operation, high yield, and low pollution.