DTPA-Assisted Selective Leaching of Mo, Co, Ni, and Al from Spent Hydrodesulfurization Catalysts

Abstract The extraction of cobalt (Co), nickel (Ni), molybdenum (Mo), and aluminum (Al) from an alumina-supported hydrodesulfurization (HDS) spent catalyst was examined using diethylene triamine pentaacetic acid (DTPA) as a chelating agent. To assess the impact of different metals on leaching efficiency, a roasting pretreatment was performed on powdered catalyst samples at various temperatures (300–700°C) and durations (15–360 min). The morphological and textural modifications before and after roasting were characterized using scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis. The optimal roasting parameters were determined to be 600°C for 180 min, under which the maximum metal extraction efficiencies were obtained: 71.05% for Mo, 80.06% for Co, 73.86% for Ni, and 15.33 % for Al. Leaching experiments were conducted with a particle size range of + 75 to − 30 µm, a liquid-to-solid ratio of 15 mL/g, a DTPA concentration of 0.2 M, a leaching temperature of 60°C, a duration of 180 min, and a stirring rate of 200 rpm. The findings highlight that both roasting temperature and time play a crucial role in enhancing metal dissolution from the spent catalyst.