ABSTRACT After the extraction of molybdenum from the spent HDS catalyst, a residue containing aluminum, nickel, cobalt, and a small amount of molybdenum was obtained. The simultaneous recovery of nickel, cobalt, aluminum, and residual molybdenum from molybdenum leach residue can be achieved through hydrochloric acid leaching. In the work presented herein, the extraction of molybdenum, cobalt, and nickel from the acidic leach solution of molybdenum leach residue was investigated. Trioctyl tertiary amine can selectively extract cobalt and molybdenum from the acidic leach solution, the extraction of both cobalt and molybdenum reached more than 99% after two-stage countercurrent extraction. The combination of pure water and 25% ammonia water can be utilised for the separation and extraction of cobalt and molybdenum from the loaded cobalt-molybdenum organic phase. After the extraction of cobalt and molybdenum, a synergistic extraction system comprising decyl 4-picolinate and dinonylnaphthalene sulfonic acid can be employed for nickel extraction, achieving a nickel extraction exceeding 99.70% while maintaining aluminum extraction at only 0.32% after undergoing four-stage countercurrent extraction. The nickel stripping efficiency can reach 99.50% after four-stage countercurrent stripping, using a stripping agent of 2 mol/L H2SO4.
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