The Roles of Reactive Species in Micropollutant Degradation in the UV/Free Chlorine System
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- 作者：Jingyun Fang ; Yun Fu ; Chii Shang
- 刊名：Environmental Science & Technology
- 出版年：2014
- 出版时间：February 4, 2014
- 年：2014
- 卷：48
- 期：3
- 页码：1859-1868
- 全文大小：409K
- ISSN：1520-5851
文摘
The UV/free chlorine process forms reactive species such as hydroxyl radicals (HO鈥?/sup>), chlorine atoms (Cl鈥?/sup>), Cl2鈥⑩€?/sup>, and O鈥⑩€?/sup>. The specific roles of these reactive species in aqueous micropollutant degradation in the UV/chlorine process under different conditions were investigated using a steady-state kinetic model. Benzoic acid (BA) was chosen as the model micropollutant. The steady-state kinetic model developed fitted the experimental data well. The results showed that HO鈥?/sup> and Cl鈥?/sup> contributed substantially to BA degradation, while the roles of the other reactive species such as Cl2鈥⑩€?/sup> and O鈥⑩€?/sup> were negligible. The overall degradation rate of BA decreased as the pH increased from 6 to 9. In particular, the relative contributions of HO鈥?/sup> and Cl鈥?/sup> to the degradation changed from 34.7% and 65.3% respectively at pH 6 to 37.9% and 62% respectively at pH 9 under the conditions evaluated. Their relative contributions also changed slightly with variations in chlorine dosage, BA concentration and chloride concentration. The scavenging effect of natural organic matter (NOM) on Cl鈥?/sup> was relatively small compared to that on HO鈥?/sup>, while bicarbonate preferentially reduced the contribution of Cl鈥?/sup>. This study is the first to demonstrate the contributions of different reactive species to the micropollutant degradation in the UV/chlorine system under environmentally relevant conditions.