Mechanochemically and Sol–Gel Synthesized ZnO Catalysts for Advanced Tribocatalytic Degradation of Cephalexin

Cephalexin is a widely used antibiotic frequently detected in hospital wastewater and aquatic environments near pharmaceutical facilities, where its persistence contributes to the spread of antibiotic resistance. Mechanically driven advanced oxidation processes, including piezocatalysis and tribocatalysis, represent sustainable alternatives for pollutant removal because they operate without external light or heat sources. In this study, ZnO catalysts with controlled morphologies were synthesized via sol–gel and mechanochemical methods using different solvents and activation times (1 and 5 h). The influence of structural characteristics, surface area, and friction conditions on catalytic performance was systematically evaluated. The results demonstrated that tribocatalytic efficiency strongly depends on stirring rate and reactor material, with PTFE systems exhibiting superior performance. Mechanochemically activated ZnO (1 h) showed the highest degradation efficiency due to optimized defect density and surface accessibility. All catalysts exhibited high stability, while radical scavenging experiments identified superoxide radicals as the primary reactive species in the degradation process.