Integrated Ion Exchange Approach for the Selective Recovery of Molybdenum, Cobalt, and Aluminum from Leachates of Spent Hydrodesulfurization Catalysts

Efficient separation and purification of individual metals from spent hydrodesulfurization catalysts remain a critical challenge in catalyst resource recovery. This study presents an integrated ion exchange strategy for the selective separation and recovery of molybdenum (Mo), cobalt (Co), and aluminum (Al) from multicomponent leachates, employing sequential anion and cation exchange resins under systematically optimized adsorption and desorption conditions. Results show that D314 anion exchange resin achieved over 99% removal of Mo even with substantial Co and Al present, while D860 cation exchange resin exhibited strong selectivity for Al over Co, reaching 38.27% adsorption for Al with minimal Co uptake. Process variables including pH, contact time, and Co and Al mass ratio significantly affected separation, with optimized conditions (pH 1.5, and 48 h) yielding a separation factor of 2255. Adsorption isotherm analysis indicated that the Langmuir model best described the process, highlighting monolayer adsorption as being dominant. Dynamic column experiments further confirmed scalability, with selective desorption realized by sequential elution using NaOH and H2SO4. The integrated approach developed here offers both mechanistic insight and practical guidance for the efficient, sustainable recovery of valuable metals from spent catalyst leachates in the petroleum refining industry.