建迅教育摘要
饮用水中的有机微污染物化学结构稳定，难以被常规饮用水处理工艺有效去除，严重影响水环境质量和饮用水安全。基于硫酸根自由基（SO4−•）的高级氧化技术对大部分污染物有很好的去除效果，紫外催化过硫酸盐(UV/PDS)可以有效的产生SO4−•，在饮用水处理领域有良好的应用前景，但是目前对于其氧化污染物的内在机制研究还不充分。
本研究围绕水体背景成分对UV/PDS氧化工艺降解莠去津（ATZ）、三氯生（TCS）和2,4,6-三氯苯甲醚（TCA）这三种典型污染物效能影响展开一系列研究，利用动力学模型研究该氧化体系中各活性成分对污染物降解贡献，对比考察UV/PDS和传统紫外催化过氧化氢工艺（UV/H2O2）去除污染物效能及其降解污染物路径的异同，最后研究ATZ的主要氧化产物产率受水体背景成分影响规律，探究高级氧化体系中二级自由基如有机自由基、碳酸根自由基（CO3−•）和活性氯自由基的性质。
UV/PDS高级氧化体系可以有效降解ATZ、TCA和TCS，其降解这三种污染物效能随PDS投加量增加而增强，而增加污染物和天然有机物（NOM）浓度会降低UV/PDS降解这几种污染物的效能。碳酸根/重碳酸根（CO32-/HCO3-）对UV/PDS降解ATZ和TCA效率有明显的抑制作用，但是其对TCS的降解效率影响不大。氯离子（Cl−）对UV/PDS降解ATZ和TCS效率有明显抑制作用，但是对TCA降解效率基本没有影响。UV/PDS氧化ATZ和TCA的效率随pH增加而降低，当pH从4增加到8时，UV/PDS降解TCS效率逐渐降低，但是当pH>8时，UV/PDS降解TCS的效率又有明显的升高。
通过自由基稳态假设建立UV/PDS氧化体系降解污染物的动力学模型，结果表明该动力学模型能够很好的拟合不同PDS投加量、目标物浓度和pH条件下UV/PDS降解三种污染物的表观速率。通过计算得到UV/PDS氧化体系中SO4−•和HO•的稳态浓度随PDS投加量增大而增加，NOM、Cl-和CO32-/HCO3-会捕获SO4−•和HO•从而导致其稳态浓度显著降低，pH增大导致磷酸根形态的变化使得水体背景成分捕获SO4−•能力增大，从而降低体系中SO4−•和HO•的稳态浓度。在UV/PDS体系中SO4−•对目标有机物降解起主要作用，而HO•贡献作用较少。UV对ATZ和TCA的直接光解作用较微弱，但是UV对TCS的降解贡献作用相对较大。NOM由于其遮光作用和对自由基捕获作用，会导致体系中自由基稳态浓度降低，从而降低UV/PDS降解污染物效率。体系中存在CO32-/HCO3-和Cl-时，SO4−•和HO•稳态浓度显著降低，反应生成的CO3−•对
ATZ和TCS具有氧化能力，而生成的活性氯可以氧化降解ATZ和TCA。
在相同操作条件下，UV/PDS对三种污染物质的降解效率比UV/H2O2高，主要是因为PDS的摩尔吸光系数和量子产率比H2O2大，NOM和CO32-/HCO3-对SO4−•和HO•都有较强捕获作用，而NOM和CO32-/HCO3-对HO•的捕获能力比其捕获SO4−•能力强。此外中性条件下Cl-对SO4−•有较强的捕获作用，但是其对HO•的捕获作用微弱，因此Cl-对UV/PDS降解污染物的抑制作用较为明显，但是其对UV/
H2O2降解污染物效率影响不大。此外这三种污染物在UV/PDS和UV/H2O2两种氧化体系中的主要氧化产物也被研究鉴定，结果表明这两种氧化体系在降解ATZ和TCA时的氧化产物种类相同，HO•和SO4−•氧化这两种污染物主要是通过电子转移反应和夺氢反应。相比较UV/PDS体系，UV/H2O2氧化TCS时更容易产生羟基化产物，表明HO•氧化污染物时羟基化作用较SO4−•要强。
UV/PDS氧化ATZ过程中产生的去乙基-阿特拉津（DEA）和去异丙基-阿特拉津（DIA）产率比值要比UV/H2O2体系中的DEA和DIA产率比值高，主要是因为SO4-•的选择性较HO•更强，其更倾向于进攻ATZ上的N-乙基官能团。NOM和HCO3-/CO32-对UV/PDS氧化体系中的DEA和DIA产率影响不大，主要是因为有机自由基和CO3−•活性较低，它们氧化ATZ上的乙基和异丙基官能团能力较弱。UV/PDS氧化体系中存在Cl-时或在碱性条件下，DEA产率略微下降，DIA的产率明显升高，导致UV/PDS氧化体系中的DEA与DIA比值显著降低，这主要是因为存在Cl-或增大pH能够促使SO4-•转化为HO•。相比较UV/PDS氧化体系，UV/H2O2氧化体系中的DEA和DIA产率受水体背景成分影响不大。此外研究结果还表明活性氯自由基与SO4-•的氧化特性较为相似，而且活性氯自由基比SO4-•氧化N-乙基官能团的选择性更强，这些结果在实际水体中也得到了很好的认证。
关键词：硫酸根自由基；紫外催化；有机微污染物；动力学模型；氧化产物；
二级自由基
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Abstract
Due to the fact that the chemical structure of micro-pollutants in drinking water are stable, they are difficult to degrade in common drinking water process. The pollutants riously affect the water quality and drinking water safety. Sulfate radical (SO4−•)-bad advanced oxidation process are effective in degrading organic contaminants in drinking water. UV photolysis of peroxydisulfate (UV/PDS), as a green SO4−• generation method, has a promising prospect in engineering application. However, it is insufficient to study on the mechanism of micro-pollutants degradation in UV/PDS process.
This rearch eks to investigate the effects of water matrix on atrazine (ATZ), 2,4,6-trichloroanisole (TCA), and triclosan (TCS) degradation by UV/PDS process. Kinetic parameters were developed in an effort to model the contributions of various reactive species in UV/PDS process under different water quality conditions. Degradation efficiencies and oxidation pathways of the model pollutants were compared between the conventional hydroxy l radical (HO•)-bad AOPs (i.e., UV photolysis of hydrogen peroxide (UV/H2O2)) and UV/PDS process. The formation of two primary products (i.e., deethylatrazine (DEA) and deisopropylatrazine (DIA)) along with the degradation of ATZ in UV/PDS and UV/H2O2process was investigated in the abnce vs prenc
龙石岛e of various water matrixes, and then the characteristics of condary reactive radicals were evaluated by monitoring the changes of the DEA to DIA ratio.
ATZ, TCA, and TCS could be degraded effectively using UV/PDS process. The removal efficiency incread with increasing the dosage of PDS, while the prence of NOM had significantly scavenge effect on the degradation of tho three compounds. Carbonate/bicarbonate (HCO3-/CO32-) played a minor role in the degradation of TCS, but it had significantly scavenge effects on the removal of ATZ and TCA. The obrved pudo-first-order rate constant for TCA degradation was slightly impacted by the prence of Cl-. But a significant inhibitory effect was obrved for ATZ and TCS removal when Cl- concentration was prent. Over the pH range of 4-9, the removal efficiencies of ATZ and TCA by UV/PDS incread with pH decreasing When pH=9, the efficiency was higher than that when pH=5~8 for TCS removal.
A simple steady-state kinetic model was developed bad on the initial rates of compounds destruction, which could well describe the apparent pudo-first-order rate constants. Modeling results shows the steady-state concentrations of SO4−• and HO• incread with increasing PDS dosage. Degradation rate of ATZ and TCA decread with pH increasing from 4.0 to 9.0, which could be explained by the lower radical
scavenging effect of dihydrogen phosphate than hydrogen phosphate under acidic conditions. The steady-state concentration of SO4−• was much higher than that of HO•, suggesting that the former played a major role for compounds destruction. UV played an important role in the TCS degradation, which was slightly impacted the ATZ and TCA degradation. NOM significantly decread the oxidation rates of target compounds due to its radical scavenging effects and UV absorption with the former one being dominant. The steady-state concentrations of SO4−• and HO• decread with the increa of CO32-/HCO3- and Cl-dosage. The generated CO3−• could react with ATZ and TCS effectively. ATZ and TCA could degraded by reactive chloride species.feckless
UV/PDS process was more effective in the degradation of the three organic micro-pollutants than the UV/H2O2 under the same conditions, mainly ascribed to the fact that the molar extinction coefficients at 254 nm and the quantum efficiency of photolysis for PDS were higher than tho for H2O2. NOM and HCO3-/CO32- showed the scavenging effect on both SO4−• and HO•, and t he inhibition was much more significant for the latter. At neutral condition, Cl- reacted with SO4−• at a higher cond-order rate constant than HO•, thus resulting in a relatively stronger scavenging effect on SO4−•. Oxidation products of the three compounds in UV/PDS and UV/H2O2 process were i
dentified. Finally the degradation pathways were tentatively propod. Results showed that same oxidation products were produced from the degradation of ATZ and TCA in the two process, suggesting that electron transfer and hydrogen abstraction played a primary role. Extra hydroxylation products were detected in the TCS degradation in UV/H2O2 process compared with UV/PDS process becau of a stronger hydroxylation for organic compounds oxidation by HO•.
auctionSO4-• displayed a more distinctive prevalence to the ethyl function of ATZ than HO•, leading to the higher ratio of DEA/DIA in UV/PDS system than that in UV/H2O2 system in pure water. The yields of DEA and DIA were not impacted by NOM or HCO3-/CO32-. Howbeit, the increa of DIA yield as well as the decrea of DEA yield were interestingly obrved in the prence of Cl- or increasing solution pH, which was attributed to the promotion of Cl- and OH- at moderate concentration (mM range) for the conversion of SO4-• into HO•. Differing from UV/PDS system, all the factors did not change DEA and DIA yields. Moreover, it was confirmed that RCs had a greater lectivity but a relatively lower reactivity on attacking the ethyl function than that of SO4-•. The findi ngs were also strengthened by monitoring the degradation of ATZ as well as the formation of DEA and DIA in three natural waters.
Keywords: sulfate radical, photocatalytic, micropollution, kinetic model, oxidation products, condar
y radical
右脑学习目录
摘要......................................................................................................................... I ABSTRACT .............................................................................................................. I II 第1章绪论 (1)
1.1 课题研究背景 (1)
滴滴涕是什么1.2 有机微污染物种类、性质和危害 (2)
1.3 有机微污染物处理工艺现状 (3)
1.3.1 生物处理技术 (3)
1.3.2 膜处理技术 (4)
1.3.3 吸附技术 (4)
1.3.4 氧化技术 (5)
1.3.5 基于HO•高级氧化技术 (6)
1.4 催化过硫酸盐技术 (11)
1.4.1 热活化过硫酸盐技术 (11)
1.4.2 碱活化过硫酸盐技术 (12)
1.4.3 微波活化过硫酸盐技术 (12)
1.4.4 过渡金属活化过硫酸盐技术 (13)
1.4.5 紫外活化过硫酸盐技术 (13)
1.5 紫外催化过硫酸盐应用前景及待研究问题 (14)
1.5.1 应用前景 (14)
契据1.5.2 待研究问题 (17)好看的外国电影推荐
1.6 研究目的和意义 (19)
1.7 技术路线 (20)
雅思考试一般都什么时间
第2章实验材料与方法 (21)
2.1 目标物选择 (21)
2.2 试剂和装置 (22)
2.2.1 实验试剂及溶液配置 (22)
2.2.2 实验装置 (24)
2.3 实验与检测方法 (24)
2.3.1 H2O2和PDS浓度的测定 (25)
2.3.2 有机微污染物浓度测定 (26)
