The electrochemical degradation of enrofloxacin using RuO2-IrO2-TiO2/Ti electrodes: Kinetics, mechanism, and model prediction

Abstract

Enrofloxacin (ENR), a prevalent antibiotic, poses a global aquatic pollution risk due to its persistence and toxicity, necessitating the development of innovative degradation methods. This study investigates the electrochemical degradation of the antibiotic ENR using RuO₂-IrO₂-TiO₂/Ti anodes. The degradation of ENR follows first-order kinetics; the main reactive species involved in the reaction were identified as hydroxyl radicals (•OH), chlorine radicals (Cl•/ Cl^2•-), and other active chlorine species, with •OH contributing the most at 85.15 %. The study systematically investigated the impact of ENR initial concentration, pH, inter-electrode distance (d), current density (j), and inorganic anions on the degradation rate and kinetics. The optimal conditions were determined to be: an initial ENR concentration of 1 μg/mL, pH of 7, d of 3 cm, and j of 3 mA/cm². Cl⁻ as reactive material precursors, has a promoting effect on the reaction; CO₃²⁻ inhibits the degradation, especially at high concentrations where the inhibitory effect is significant. By combining the electrochemical prediction of active sites (CN, CO, CF) and the identified disinfection byproducts (chloroform, dichloroacetic acid, dichloroacetonitrile), a reaction mechanism was proposed where radicals attack and open the piperazine and quinolone rings of ENR. In comparison with the predictive outcomes of Back Propagation (BP), Particle Swarm Optimization-Back Propagation (PSO-BP), and Long Short-Term Memory (LSTM) neural networks, the determination coefficients (R²) were 0.8483, 0.8499, and 0.9153. This study offers a scientific foundation for electrochemical oxidation theory and practice and provides new ideas for predictive control in electrochemical treatment systems.