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 •O 2− 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 CO 2 and H 2 O. This research provides experimental and theoretical support for scaling up ECO systems in antibiotic-laden wastewater treatment. Graphical This study demonstrates efficient roxithromycin degradation via electrocatalytic ozonation using Ru-Ir electrodes in a novel internal circulation reactor, achieving complete removal in 60 min with synergy factor 1.21. •OH radicals dominate oxidation, leading to mineralization through three pathways.