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紫外高级还原技术对饮用水消毒副产物三氯乙酰胺的降解效能研究

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2019/9/3 10:03:52  

摘要:卤乙酰胺(HAcAms)是一类具有高细胞毒性和高遗传毒性的饮用水含氮消毒副产物(N-DBPs),并在饮用水中被广泛检出,其中三氯乙酰胺(TCAM)的毒性显著高于传统DBPs。由于之前的研究多侧重于HAcAms的生成机理以及从源头控制HAcAms的生成,而对于已经生成并存在的HAcAms的末端控制研究较少,因此迫切需要寻找能有效降低水中HAcAms的技术。论文选取三种基于UV的高级还原技术降解水中的TCAM,探究了常见饮用水本底组份对反应的影响、TCAM的降解机理以及其降解动力学模型。为了更好的探究三种高级还原技术对其他具有CX3-R结构的DBPs的降解效果,以TCM、CH、TCAN作为目标污染物,降解率作为检测指标,进行基于UV的高级还原技术研究。

研究表明,UV/亚硫酸钠、UV/次亚磷酸钠以及UV/连二亚硫酸钠体系在一定条件下均具有脱氯的能力。在探究TCAM的降解机理时发现,在UV/亚硫酸钠和UV/次亚磷酸钠体系中eaq-起主要作用,在UV/连二亚硫酸钠体系中SO2·-起主要作用,推测TCAM在三种高级还原体系的作用下C—Cl键断裂,氯离子离去,降解产物分别为2-磺酸基-2,2-二氯乙酰胺、2-偏亚磷酸基-2,2-二氯乙酰胺以及2-亚磺酸基-2,2-二氯乙酰胺。由于考虑到基于UV的高级还原技术在实际中的应用,论文探究了常见饮用水本底组份对反应的影响,包括:光照强度、还原剂投加剂量、溶液初始pH。研究发现,TCAM的降解率随着光照强度的提高、还原剂剂量的增加以及溶液初始pH的升高而升高,其中溶液初始pH对反应的影响最大,UV/亚硫酸钠体系效果最佳,UV/连二亚硫酸钠体系次之。通过多次的对比分析,发现在pH为9,亚硫酸钠投加剂量为1.00 mmol·L-1,UV光照强度为450 μW·cm-2的条件下,UV/亚硫酸钠体系可经济、快速降解TCAM。

通过试验了解三种高级还原体系对CX3-R型(TCM、CH、TCAN与TCAM具有相似结构)DBPs的降解效果,试验证明:在降解TCM、CH、TCAN的研究中,UV/连二亚硫酸钠体系效果最佳,UV/亚硫酸钠体系次之。结果表明在UV光照强度为450 μW·cm-2、连二亚硫酸钠投加剂量为1.00 mmol·L-1、溶液初始pH为7的条件下,反应30 min时,UV/连二亚硫酸钠体系对TCM、CH、TCAN的降解率均高于80%。

Haloacetamides (HAcAms) are a class of nitrogen-containing disinfection by-products (N-DBPs) in drinking water with high cytotoxicity and high genotoxicity, and are widely detected in drinking water, among which the toxicity of trichloroacetamide (TCAM) is significantly higher than traditional DBPs. Since previous studies have focused on the generation mechanism of HAcAms and control the generation of HAcAms from the source, and there are few studies on the terminal control of HAcAms that have been generated and existed, it is urgent to find a technique that can effectively reduce HAcAms in water. The paper selected three UV-based advanced reduction techniques to degrade TCAM in water, and explored the effects of common drinking water background components on the reaction, TCAM degradation mechanism and its degradation kinetic model. In order to better explore the degradation effects of the three advanced reduction technologies on other disinfection by-products with CX3-R structure, we set TCM, CH and TCAN as target pollutants, degradation rate as a detection index and explore the UV-based advanced reduction processes research which has the degradation rate as adetection index.

Studies have shown that UV/sodium sulfite, UV/sodium hypophosphite and UV/sodium dithionite system can have the ability to dechlorinate under certain conditions. In exploring the degradation mechanism of TCAM, it was found that eaq- plays a major role in the UV/sodium sulfite and UV/sodium phosphite systems, and SO2·- plays a major role in the UV/sodium dithionite system. Based on the above, it is speculated that TCAM’s C—Cl bond is broken under the action of these three advanced reduction systems, and the chloride ions was removed. The degradation products are 2-sulfonic acid-2,2-dichloroacetamide and 2-metaphosphoryl-2,2-dichloroacetamide. And 2-sulfinyl-2,2-dichloroac -etamide. Considering the practical application of UV-based advanced reduction processes, the paper explores the effects of common drinking water background components on the reaction, including: light intensity, reducing agent dosage, initial pH of the solution. It was found that the degradation rate of TCAM increased with the increasing of light intensity, reducing agent dosage and the initial pH value of the solution. In fact, the initial pH value of the solution had the most influence on the reaction. In the study of TCAM degradation, the effect of UV/sodium sulfite system is the best, followed by UV/sodium dithionite system. Through multiple comparative analysis, it was found that the UV/sodium sulfite system can remove TCAM economically and rapidly under the condition of pH 9, sodium sulfite dosage of 1.00 mmol·L-1 and UV light intensity of 450 μW·cm-2.

Degradation effects of three advanced reduction systems on CX3-R type DBPs (TCM, CH, TCAN and TCAM have similar structures) were investigated by experiments. In the degradation of TCM, CH, and TCAN study, the UV/sodium dithionite system worked best, followed by the UV/sodium sulfite system. The experimental results show that the UV/sodium dithionite system is obtained at a UV light intensity of 450 μW·cm-2, a sodium dithionite dosage of 1.00 mmol·L-1, and an initial pH of 7 for 30 min. The degradation rates of TCM, CH and TCAN were all higher than 80%.

关键词:三氯乙酰胺;消毒副产物;紫外;高级还原技术;降解机理

trichloroacetamide; disinfection by-product; ultraviolet; advanced reduction processes; degradation mechanism

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