In situ fabrication of oxygen-vacancy-rich flower-like cerium–lanthanum oxide/HZSM-5 composites from waste polishing powder for dichloromethane degradation

This study addresses the challenges in recycling rare earth polishing powder waste (REPPWs)—such as harsh leaching conditions, poor morphology control, and low value-added output—by proposing a synergistic “leaching-morphology control-zeolite loading” strategy. This approach enabled the successfully synthesize of flower-like Ce Ov La/HZSM-5 composite catalyst using polishing powder as the primary raw material. This strategy involves three key elements: 1) co-leaching Ce 3+ /La 3+ with a H 2 SO 4 -ascorbic acid system, 2) precisely constructing Ce Ov La with abundant oxygen vacancies (Ovs) via controlled oxalic acid addition, and 3) obtaining the final catalyst by in-situ HZSM-5 growth on the Ce Ov La. Density functional theory (DFT) calculations revealed that La doping reduced the formation energy of Ovs within the CeO 2 lattice. Moreover, the incorporation of HZSM-5 further decreased this energy barrier while also provided abundant acidic sites. The synergistic interaction between these components enhanced the electronic environment and dispersion of active sites, thereby significantly promoting C Cl bond cleavage and deep oxidation of dichloromethane (DCM). Experimental results demonstrated that the catalyst achieved 81.8% DCM conversion at 450 °C, with over 99% CO 2 selectivity and minimal Cl 2 byproduct formation. This work offers new insights into the value-added utilization of REPPWs and the efficient degradation of chlorinated volatile organic compounds (CVOCs). Download: Download high-res image (227KB) Download: Download full-size image