(General session) Mineral processing / Environment / Recycling

[2K0401-14-13] [Student presentation: Master’s course] Alkaline Amino Acid Leaching for Selective Recovery of Molybdenum and Cobalt from Spent Mo/Co-catalyst

○Idol Phann¹, Naoko Okibe¹ (1. Kyushu University)

司会：松本和也（秋田大学）

Keywords:spent hydrodesulfurization (HDS) catalyst, Molybdenum (Mo), Cobalt (Co), amino acid leaching, alanine

Spent catalysts are generated in large quantities as solid waste yearly by oil refinery industries and are regarded as hazardous yet valuable waste materials. Particularly, spent hydrodesulfurization (HDS) catalyst represent a potential source for some critically rare metals. The recycling of these wastes is critical to minimize environmental pollution and to reuse the resource. This study focused on recovering secondary metal values (Mo and Co) from the spent Co/Mo hydrodesulfurization catalyst using the more environmentally friendly leaching lixiviant. In this study, the effect of alanine addition (0.5 M) in alkaline leaching environment (pH 11) is discussed. The dissolution of Mo from the spent catalyst was mainly through the alkaline-leaching effect, but the advantage of alanine was to maintain the alkalinity of the system through its natural buffering effect and to chelate with Co and precipitate as Co-alanine complex to be recovered in a sequential three-steps leaching process. The final cumulative recoveries of Mo and Co were 99.7% and 91.6%, respectively, at a pulp density of 3%. Selective recovery of Mo and Co was achieved by using alkaline-alanine lixiviant, as the dissolution of unwanted Al was mostly suppressed. Overall, the study showed the potential of using amino acids as alternative lixiviants to selectively recover metals from the waste materials.