Electrocatalytic Ozonation Roxithromycin in Aqueous Solution: Synergistic Effect and Mechanism.

This study explores efficient degradation of roxithromycin (ROX), a persistent macrolide antibiotic in aqueous solution, using electrocatalytic ozonation (ECO) technology. High-performance Ru-Ir electrode (1:4-M ratio) was prepared by thermal decomposition on titanium substrate. Characterization showed mud-crack morphology with rough porous surface enhancing electrocatalytic activity, oxygen evolution overpotential (1.40-1.60 V), chlorine evolution overpotential (1.30-1.40 V), and superior stability (charge transfer resistance 14.38 Ω). A novel internal circulation reactor was engineered with ozone or reaction solution as fluidizing medium to boost mass transfer efficiency, prolong pollutant residence time, and optimize ozone utilization. Synergistic ECO resulted in complete ROX removal within 60 min, outperforming individual processes. Optimal parameters (current density 10 mA·cm-2) achieved synergy factor of 1.21 and coordination index of 2.78. Radical quenching experiments and UPLC-QTOF/MS analysis confirmed •OH as primary oxidant, with •O2- and ozone contributions, and proposed three plausible degradation pathways involving oxidative attacks on nitrogen-containing heterocycles, glycosidic bonds, and macrolide ring leading to cleavages, rearrangements, and ultimate mineralization into CO2 and H2O. This research provides experimental and theoretical support for scaling up ECO systems in antibiotic-laden wastewater treatment.