In-situ recovery of Pd from spent automotive catalysts: Preparation of high-value Pd/AC by vacuum vaporization-deposition.

Recovering precious metals from spent automotive catalysts and realizing their high-value reuse is critical to ease resource shortages and advance sustainable industrial development. Conventional pyrometallurgical recovery consumes massive energy and generates secondary pollution; most existing techniques only extract Pd without exploring its subsequent high-value application. In this study, we developed an effective and green vacuum vaporization-deposition approach for the in-situ recovery and high-value utilization of palladium (Pd) from spent automotive catalysts. Under 1573 K and < 0.01 Pa, Pd was successfully transferred from spent automotive catalysts onto activated carbon (AC), enabling the preparation of a high-value Pd supported on activated carbon (Pd/AC) catalysts with a Pd loading of 61.42 mg/kg. During the process, no hazardous sulfur oxides such as SO2 were detected, and sulfur was predominantly released in the form of low-toxicity organosulfur compounds, effectively avoiding secondary environmental pollution caused by toxic sulfur oxide emissions. Based on theoretical adsorption simulations, the loading mechanism of Pd on AC is verified: Pd vaporized under the experimental conditions, was readily adsorbed by the defect sites of AC, and ultimately deposited on the AC surface following a vacancy defect adsorption pathway. The prepared Pd/AC exhibited uniformly dispersed Pd particles and demonstrated significantly enhanced hydrogen desorption ability and reduction performance. This work provides a novel approach for in-situ metal recovery and high-value reutilization of solid waste containing precious metals.