Abstract:Hydrodesulfurization catalysts (HDS) play an important role in the improvement of petroleum quality, but they are converted into waste catalysts due to sintering and deactivation after long-term use and become HW50 hazardous waste. The production of spent HDS catalysts in China is huge and has significant environmental pollution risks. Vanadium (V) and molybdenum (Mo) are the key components of spent HDS catalysts. Although the traditional sodium roasting process can effectively recover these metals, the process consumes a large amount of alkali and requires high temperature (>800 °C). Therefore, it is urgent to explore low-carbon recovery methods. This study reveals the influence of electrochemical condition changes on the leaching mechanism of V and Mo in spent HDS catalysts in mild alkaline media through thermodynamic calculations and experimental research. It is found that the migration and transformation of V and Mo could be achieved by adjusting the redox potential (Eh) and pH value of the system, and they are stable in the form of Na2V2O7 and Na2Mo2O7 in the alkaline medium. The experimental optimization results show that the leaching rate of V and Mo reaches 85.43% and 82.47% respectively under the conditions including leaching temperature of 20 °C, voltage of 3 V, leaching time of 6 h, NaOH concentration of 1 mol/L and liquid-solid ratio of 10:1. The leaching process conforms to the mass transfer controlled kinetic model, and the electrochemical condition regulation effectively promotes the generation of reactive oxygen species, significantly improving the leaching efficiency of low-valent metals on the solid surface.This study provides an innovative technical approach for the efficient recovery of valuable metals from spent HDS catalysts under mild conditions.