The Degradation of Aqueous Oxytetracycline by an O3/CaO2 System in the Presence of HCO3−: Performance, Mechanism, Degradation Pathways, and Toxicity Evaluation

This research constructed a novel O3/CaO2/HCO3− system to degrade antibiotic oxytetracycline (OTC) in water. The results indicated that CaO2 and HCO3− addition could promote OTC degradation in an O3 system. There is an optimal dosage of CaO2 (0.05 g/L) and HCO3− (2.25 mmol/L) that promotes OTC degradation. After 30 min of treatment, approximately 91.5% of the OTC molecules were eliminated in the O3/CaO2/HCO3− system. A higher O3 concentration, alkaline condition, and lower OTC concentration were conducive to OTC decomposition. Active substances including ·OH, 1O2, ·O2−, and ·HCO3− play certain roles in OTC degradation. The production of ·OH followed the order: O3/CaO2/HCO3− > O3/CaO2 > O3. Compared to the sole O3 system, TOC and COD were easier to remove in the O3/CaO2/HCO3− system. Based on DFT and LC-MS, active species dominant in the degradation pathways of OTC were proposed. Then, an evaluation of the toxic changes in intermediates during OTC degradation was carried out. The feasibility of O3/CaO2/HCO3− for the treatment of other substances, such as bisphenol A, tetracycline, and actual wastewater, was investigated. Finally, the energy efficiency of the O3/CaO2/HCO3− system was calculated and compared with other mainstream processes of OTC degradation. The O3/CaO2/HCO3− system may be considered as an efficient and economical approach for antibiotic destruction.