| Author: | Li, Yaru |
| Title: | Degradation of antibiotics by advanced oxidation processes under irradiation of VUV and UV light |
| Advisors: | Tsang, Chiu-wa (CEE) |
| Degree: | M.Sc. |
| Year: | 2016 |
| Subject: | Hong Kong Polytechnic University -- Dissertations Sewage -- Purification -- Oxidation Antibiotics -- Environmental aspects |
| Department: | Faculty of Construction and Environment |
| Pages: | xi, 68 pages : color illustrations |
| Language: | English |
| Abstract: | Antibiotics, extensively used in human and veterinary therapy, could only be metabolized partially in the bodies of organism and evacuated into environment. Unfortunately, most kinds of antibiotics can exist in aquatic matrix for a long time due to their persistence against biological degradation. It is urgent to removal antibiotics from aquatic environment to avoid their adverse effects of antibiotic resistance and ecotoxicity. Three antibiotics, cefalexin (CEX), norfloxacin (NOF) and ofloxacin (OFX), which predominated among 16 investigated antibiotics in many sewage treatment plants in Hong Kong, were selected as probes for Advanced Oxidation Processes (AOPs) in this study. The comparison reaction of degradation of antibiotics by VUV or UV-based processes were conducted.The results indicated that the photooxidation of antibiotics fit to a psedo-first-order kinetic model. It is easily to observe that VUV-based processes were more efficient than UV-based processes for antibiotics degradation. Although sole VUV irradiation could achieve pretty high removal efficiency of 10 mg/L CEX, NOF and OFX with enough time, the addition of peroxides enhanced the AOPs apparently. While, no significant degradation of antibiotics was observed in the present of H₂O₂ or K₂S₂O₈ in dark controls. S2O82- could obtain higher reaction rate constant than H₂O₂ for the degradation of OFX and NOF in various processes followed the order: VUV/K₂S₂O₈ > VUV/ H₂O₂ > UV/K₂S₂O₈ > UV/ H₂O₂ > VUV > UV. For CEX decompose, however, the performance of H₂O₂ was better than that of S₂O₈²⁻. In addition, CEX was the easiest one to be degrade, while, OFX was least likely to be decomposed by AOPs among three selected antibiotics due to different structures.Investigation of the effects of various parameters including H₂O₂ dosage, K₂S₂O₈ dosage solution pH value on the OFX degradation by VUV/H₂O₂ and VUV/K₂S₂O₈ was also conducted. The degradation rate of OFX improved when the dosage of H₂O₂ or K₂S₂O₈ increased properly. The best OFX removal efficiencies were obtained in the pH-unadjusted and pH=3 conditions in both VUV/H₂O₂ and VUV/K₂S₂O₈ processes. The dosage of H₂O₂ and K₂S₂O₈ were found to be the significant variables for OFX removal after employing Responsible Surface Methodology (RSM). According to the process optimization, the optimal conditions for OFX degradation were 0.82 and 0.97mM H₂O₂ and K₂S₂O₈, respectively, with a rate constant of 2.89 min-1, when both peroxides were added. Chloride ions in water could render the VUV/H₂O₂ inefficient for OFX degradation, while, sole chloride or bromide ions did not affect the kobs of OFX degradation by VUV/K₂S₂O₈ process. However, co-existing chloride and bromide enhanced the reaction constants of OFX in both VUV/H₂O₂ and VUV/K₂S₂O₈ processes. Interestingly, the present of sole chloride or bromide and co-existing chloride and bromide enhanced the reaction constants of NOF by sole VUV irradiation photolysis. Whereas, halides had minimal effects on the CEX degradation by sole VUV irradiation processes. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 991021952833003411.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 1.7 MB | Adobe PDF | View/Open |
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