Mineralization Of The Antibiotic Ciprofloxacin By Photoelectro-Fenton Treatment Under The Microwave Electrodeless Lamp Irradiation

The pollution caused by the manufacture and consumption of antibiotic pharmaceuticals has attracted intensive concerns among academic communities. Photo-Fenton process, i.e. Fenton oxidation under UV irradiations, has been employed to remove these antibiotics in different waste streams, during which the selection of irradiation source is of crucial importance. In the present study, a novel microwave electrodeless lamp (MWEL) was introduced in the photo-Fenton process to mineralize a widely used antibiotic, Ciprofloxacin (CIP). In the thesis, the influence of different operation conditions on the mineralization of the CIP, the optimal reaction conditions, were carried out. The primary degradation products and possible degradation pathway were elucidated. Finally, experiments of alternative iron source and the initial pH were conducted. Based on the results aforementioned, the main conclusions can be drawn as follows:(1) The paper compares the effects of photolysis, oxidation, electrochemical production of hydrogen peroxide, electrical Fenton different processes and MWEL-PEF on the degradation kinetics of CIP and TOC removal performance. The results indicate that MWEL-PEF process obtained the highest TOC removal, and the degradation kinetics follows the pseudo-first order reaction, with a higher reaction rate coefficient.(2) The paper examines the influence of current intensity, initial pH, Fe2+dosage on the CIP removal performance by single factor assays. The results showed that the optimal reaction conditions are current0.36A, pH value of3.0, Fe2+dosage concentration1.0mmol/L, initial CIP concentration of200mg/L. Under the optimized operating conditions,76.2%TOC removal could be gained after360min MWEL-PEF oxidation.(3) This paper analyzes the mechanism of degradation products of CIP in MWEL-PEF system. The paper showed that H2O2could directly generate·OH under the microwave lamp irradiation, and microwave irradiation would promote the decomposition of CIP, thus improving the mineralization of non-biodegradable antibiotics by MWEL-PEF. By UPLC-QTOF-MS/MS and size exclusion chromatography techniques, seven main intermediate products and two small molecular weight organic molecules have detected in the degradation process of CIP by MWEL-PEF. On this basis, the paper proposed the possible degradation pathway of CIP in MWEL-PEF.(4) In order to simplify the operation and increase the Fenton reaction performance, the paper also attempted to change the source of supply of iron in MWEL-PEF by internal solid-state iron (ISSI). The result showed that ISSI could supply Fe+continuously into the solution, which catalysis the decomposition H2O2into·OH, and that similar CIP and TOC removal could be obtained. Moreover, a satisfactory degradation efficacy could be gained with an initial pH value of6.0. The balance between the dissociation of ferric ions from the ISSI, consumption rates of ferric ions in MWEL-Fenton reaction, and the oxidation rate of Fe2+is a crucial factor controlling the degradation of refractory substances in MWEL-PEF process.