Advanced Oxidation Processes (AOP) for Methylene Blue Degradation Using ZnO₇₅%-CdO₂₅% Composite Nanocatalysts

This study examines the photocatalytic degradation of Methylene Blue (MB) using zinc oxide-cadmium oxide (ZnO₇₅%-CdO₂₅%) composite nanocatalysts in both pristine and lemon-functionalized forms. The heterojunction composite demonstrated superior catalytic performance compared to pure oxide systems, achieving degradation efficiencies of 76.35% (uncapped) and 89.52% (lemon-capped) after 165 minutes of UV irradiation. The enhanced activity results from improved charge carrier separation at the heterojunction interface and surface modification through natural capping agents. Kinetic analysis confirmed pseudo-first-order reaction mechanisms, with the capped catalyst exhibiting rate constants approximately 2.5-fold higher than pure ZnO systems. These findings demonstrate the potential of mixed-oxide heterojunctions combined with green surface functionalization strategies for water treatment applications.