Acid-free process for selective and efficient recovery of molybdenum from spent hydrodesulfurization catalysts

The spent hydrodesulfurization catalyst represents a significant hazardous solid waste due to its heavy metal content, necessitating stringent treatment protocols. Current commercial treatment methodologies predominantly employ substantial quantities of hydrochloric and sulfuric acids, resulting in severe secondary pollution, including challenging wastewater treatment and excessive sulfur and carbon emissions. This study introduces an innovative acid-free process for the treatment of spent catalysts, encompassing mineral phase reconstruction, acid-free water leaching, and solvent extraction. This novel approach achieves efficient separation and recovery of molybdenum, with a molybdenum-aluminum separation coefficient of 19,258.26 and a molybdenum recovery rate of 98.95%. The purity of the molybdenum product attained through single-stage extraction is 93.83%, which increases to 99.7% with three-stage extraction. Life cycle assessment indicates that this process reduces CO₂ emissions by 42.4% and SO₂ emissions by 73.7% compared to traditional methods. From the perspectives of environmental protection, energy conservation, and carbon reduction, this advanced process holds substantial industrial applicability.