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

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 degrees 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 degrees 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 mu m, a liquid-to-solid ratio of 15 mL/g, a DTPA concentration of 0.2 M, a leaching temperature of 60 degrees 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.