The Degradation of Aqueous Oxytetracycline by an O/CaO System in the Presence of HCO3-: Performance, Mechanism, Degradation Pathways, and Toxicity Evaluation.

This research constructed a novel O/CaO/HCO3- system to degrade antibiotic oxytetracycline (OTC) in water. The results indicated that CaO and HCO3- addition could promote OTC degradation in an O system. There is an optimal dosage of CaO (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 O/CaO/HCO3- system. A higher O concentration, alkaline condition, and lower OTC concentration were conducive to OTC decomposition. Active substances including ·OH, O, ·O2-, and ·HCO3- play certain roles in OTC degradation. The production of ·OH followed the order: O/CaO/HCO3- > O/CaO > O. Compared to the sole O system, TOC and COD were easier to remove in the O/CaO/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 O/CaO/HCO3- for the treatment of other substances, such as bisphenol A, tetracycline, and actual wastewater, was investigated. Finally, the energy efficiency of the O/CaO/HCO3- system was calculated and compared with other mainstream processes of OTC degradation. The O/CaO/HCO3- system may be considered as an efficient and economical approach for antibiotic destruction.