Process Intensification and Multivariable Interaction Analysis for Platinum Extraction from Spent Catalysts Using Ultrasound-Assisted Leaching

The efficient recovery of platinum (Pt) from spent catalysts is of critical strategic importance to alleviate resource scarcity and supply chain dependencies. This study developed an ultrasonic-assisted leaching process using a H2SO4-NaCl system for Pt extraction from spent petroleum catalysts. Single-factor experiments were first conducted to identify the preliminary effects of key parameters. Subsequently, Response Surface Methodology (RSM) based on a Box–Behnken design was employed to model and optimize the interactive effects of ultrasonic power, sulfuric acid concentration, leaching time and NaCl concentration. The results demonstrated that ultrasonic power had the most significant influence on Pt leaching efficiency. The optimized conditions were determined as ultrasonic power of 300 W, H2SO4 concentration of 60%, leaching time of 100 min, and NaCl concentration of 0.10 mol/L. Under these optimal parameters, the Pt leaching rate reached approximately 99.8%, validating the model’s high accuracy and reliability. This work provides an efficient and stable technical pathway for the sustainable recycling of platinum from secondary resources.