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 CaO2andHCO3−addition could promote OTC degradation in an O3system. There is an optimal dosage of CaO2(0.05 g/L) andHCO3−(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 O3concentration, 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 O3system, 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.