Amoxicillin Wastewater Degradation By Combined Electrolysis With Ozone: A Kinetic And Mechanism Study

Antibiotics are widely used for curing human and veterinary diseases, as well as feed additives for livestock growth. Due to the potential adverse effects on aquatic ecology and human health, the present of antibiotics in aquatic environments received special concern. Due to the antibacterial nature and its toxicity, antibiotics show resistance to conventional biological water treatment methods. Thus, it is necessary to develop efficient treatment techniques to prevent antibiotics appearing in aquatic environment.In this study, Amoxicillin(AMO) degradation was investigated using electrolysis, ozonation, and electro-peroxone(E-peroxone) process. E-peroxone process was found to be the most effective for AMO degradation. Only 37% AMO was removed after 6 min treatment by electrolysis. While, AMO was completely degraded within 5 min and 4 min by ozonation process and E-peroxone process, respectively. In addition, 67.8% total organic carbon(TOC) mineralization was obtained after 60 min by E-peroxone treatment. In comparison, only 47.3% and 3.1% TOC mineralization were obtained using individual ozonation and electrolysis process, respectively. It was found that hydroxyl radical production and O3 utilization were enhanced in E-peroxone process. In order to control the E-peroxone treatment of Amoxicillin process efficiently and economically, important operating parameters such as O3 concentration, current, and solution p H on the process performance were evaluated systematically. It showed that increasing the O3 concentration in the sparged gas enhanced both amoxicillin degradation and TOC mineralization in the E-peroxone process. Amoxicillin degradation and TOC mineralization increased as the applied current increased from 100 to 300 m A. However, further increasing the current to 400 m A did not enhance amoxicillin degradation and TOC mineralization accordingly. It was found that p H played an important role in AMO degradation and TOC mineralization, which not only affecting the decomposition of aqueous O3 and the hydroxyl radical production, but also the existing forms of AMO. The highest removal rates were obtained at p H= 9, indicating p H control was crucial in Eperoxone process.The degradation mechanism of AMO and the strengthening mechanism of electricity in E-peroxone were also determined in this dissertation. It was proved that in E-peroxone process, considerable amounts of ?OH could be produced, and higher utilization rate of O3 was obtained as well. Therefore, it could be a reasonable interpretation for E-peroxone process performing more effective and economical than ozonation process for AMO degradation.At last, oxidation intermediates were identified in E-peroxone process and ozone process using UPLC-MS/MS. 15 intermediates were identified in E-peroxone process while 10 intermediates were detected in ozone process. It was indicated that the introduction of electrolysis in ozonation has enhanced AMO cleavage and hence its degradation. Different pathways of AMO degradation were proposed, including the hydroxylation of the benzoic ring and N, the four-membered β-lactamic ring opening, the oxidation of S, and other bond cleavage reactions.