硫代硫酸根基于含硫自由基促进五氯苯酚光解脱氯的效率及机理研究

卤代有机物的毒性源于结构中的C-X键，由于五氯苯酚结构中含有C-Cl键，环境中五氯苯酚的出现会严重威胁人类的健康，因此，对其降解脱氯的研究备受关注。本项目拟系统地研究水溶液中硫代硫酸根促进五氯苯酚紫外光解脱氯的效率及机理。首先探究五氯苯酚的紫外光解过程，考察水合电子和氢氧根的重要性，确认引发结构释放氯离子的关键因素；然后引入硫代硫酸根，明确五氯苯酚脱氯效率的提高，并基于理论和实验的结果，完整地研究紫外光解过程中五氯苯酚与硫代硫酸根的反应机理，详细考察含硫自由基在脱氯过程中的作用，阐明含硫自由基是脱氯效率提高的核心所在；最后确认硫代硫酸根和五氯苯酚的最优投加比，揭示紫外光强度、温度及共存微粒（溶解氧、碳酸根及碳酸氢根、腐殖酸）对硫代硫酸盐/UV体系脱氯效率的影响，调控实际水体中五氯苯酚的脱氯反应，实现其高效脱氯。本项目的实施将会为后续开发卤代有机物相关的水处理过程提供重要的理论和实验基础。

The toxicity of halogenated organic compounds is rooted in the C-X bond(s) (X represents halogen atom) in the structures. With C-Cl bonds in the structure of pentachlorophenol, its occurrence in the environment will greatly threaten the human health, thus more and more attention has been paid to the degradation and dechlorination of pentachlorophenol. Herein, a systematical investigation into the efficiency and mechanism of ultraviolet (UV) photolysis dechlorination of pentachlorophenol promoted by thiosulfate in aqueous solution will be conducted in this project. Firstly, the investigation will focus on the UV photolysis of pentachlorophenol to explore the significance of hydrated electron and hydroxyl ion, which can help to confirm the critical factor inducing the chloride ion ejection. Secondly, the promotion of dechlorination with addition of thiosulfate ion will be clarified. Furthermore, the mechanism of reaction of pentachlorophenol with thiosulfate ion under UV irradiation will be thoroughly studied based on the theoretical and experimental results. The roles of sulfur-containing radicals (i.e., thiosulfate radical ion, sulfite radical ion and sulfide radical ion) in the dechlorination of pentachlorophenol will be examined in detail. These results will illuminate that the release of sulfur-containing radicals is the key to promoting the dechlorination in the thiosulfate/UV system. Finally, the optimal concentration ratio of thiosulfate/pentachlorophenol will be confirmed, and this project will reveal the influence of UV intensity, temperature and coexisting particles (i.e., dissolved oxygen, carbonate/bicarbonate and humic acid) on the dechlorination of pentachlorophenol by thiosulfate/UV system, and the dechlorination of pentachlorophenol in natural waters will be optimized to ensure the efficiency. The investigation in this project will provide important theoretical and experimental foundations for the subsequent development of water treatment processes for halogenated organic compounds.