Process and Kinetics of V and W Leaching from Spent SCR Catalysts via Pressure Alkali Leaching

The efficient and selective recovery of vanadium (V) and tungsten (W) from spent SCR catalysts is challenging due to their tight encapsulation within the TiO₂ matrix and the high risk of Ti codissolution in conventional leaching processes. This study employed a synergistic leaching process using weak and strong alkalis to extract V and W from spent SCR catalysts, while Ti remained in the residue phase. Under the optimized conditions of a temperature of 180 °C, a liquid-to-solid ratio of 3:1, NaOH concentration of 1.5 mol/L, Na₂CO₃ concentration of 2 mol/L, and a leaching time of 1.5 h, the leaching efficiencies of V and W reached 96.21% and 91.05%, respectively, whereas the leaching efficiency of Ti was less than 1%. Based on the shrinking core model, the leaching processes for both V and W were determined to be controlled by solid film diffusion. The apparent activation energies for the leaching reactions of V and W were calculated to be 1.83 kJ·mol^-1 and 4.93 kJ·mol^-1, respectively. This research provides a valuable reference for enhancing the comprehensive utilization of spent SCR catalysts through industrial synergistic alkali leaching processes.