【作者】 汪应灵；

【导师】 刘国光；

【作者基本信息】 河南师范大学 ， 环境科学， 2015， 博士

【摘要】 近年来,非甾体消炎药双氯芬酸作为新兴污染物经常在水源水中,甚至饮用水中被检测到,且含量较高。研究表明,双氯芬酸药物是一种难以生物降解的环境污染物,传统的絮凝、沉淀和砂滤过程对其去除率并不高,导致部分污染物进入到自来水消毒阶段。二氧化氯和高铁酸盐是两种新型多功能强氧化剂和水处理剂,常用于地表水、地下水的消毒及传统消毒工艺的预氧化过程,能够有效去除饮用水中许多无机和有机污染物,然而矿化效果不佳,很可能转化为其它更有毒的中间产物,对饮用水安全存在着潜在风险。本文以非甾体消炎药双氯芬酸为模拟污染物,选取ClO2和K2FeO4为典型消毒剂,系统研究了双氯芬酸分别在两种消毒剂作用下的去除效果和反应动力学,探讨了降解产物、反应机理及毒性变化特点,为两种消毒剂实际应用于饮用水处理提供理论指导和技术支持。1.研究了ClO2氧化双氯芬酸的反应动力学、去除效果及影响因素。结果表明,ClO2能够快速有效降解水体中的双氯芬酸,氧化反应遵循二级反应动力学。在pH 7.0,反应温度为25℃条件下,反应速率常数为1.50×103 M-1·s-1。反应速率常数和降解率受pH值的影响不大,但却随ClO2浓度和反应温度的增加而明显增大,反应的活化能、焓变和熵变分别为7.87 kJ·mol-1、5.38 kJ·mol-1、-165.75 J·mol-1·K-1。不同种类的共存物质对ClO2氧化双氯芬酸反应的影响也不同:NO3-、Cl-、Br-、Ca2+、Fe3+和表面活性剂CTAB等共存因子对反应起一定程度的促进作用,而NH4+、NO2-、I-、Fe2+、表面活性剂SDBS、Tween-80及腐殖酸的存在能够抑制双氯芬酸的降解;SO42-、Mg2+的存在对反应几乎无影响。论文对各种影响因素的影响机制进行了具体分析。2.探讨了ClO2氧化双氯芬酸的反应机理、毒性变化及TOC去除效果。通过UPLC-MS和1H-NMR等方法鉴定出了9种双氯芬酸的氧化产物,发现羟基取代、氯代及苯环脂肪支链上的脱羧反应为主要的反应途径,ClO2直接氧化是双氯芬酸降解的主要机理,O2·-自由基对反应有部分贡献。随着ClO2剂量的增加,溶液的TOC去除率不断增大,而对明亮发光杆菌的毒性却先增大后减小,表明反应过程中生成了毒性更强的中间产物,其中酚类衍生物和醛基化产物为毒性主要贡献者。3.研究了Fe(Ⅵ)氧化双氯芬酸的反应动力学、去除效果及影响因素。结果表明,Fe(Ⅵ)也能够有效氧化降解水体中的双氯芬酸,比ClO2要慢一些,反应仍遵循二级反应动力学模式。当pH 9.0,反应温度为25℃时,反应速率常数为5.04 M-1·s-1。pH值、反应温度和Fe(Ⅵ)投加量对Fe(Ⅵ)氧化双氯芬酸反应影响显著,在pH 7.0~11.0范围内,反应速率常数和降解率随pH值的升高而逐渐降低,其中HFeO4-和FeO42-与双氯芬酸之间的比反应速率常数分别为16.8 M-1·s-1和3.61 M-1·s-1,前者占主导地位。Fe(Ⅵ)氧化双氯芬酸的活化能、焓变和熵变分别为23.3 kJ·mol-1、20.9 kJ·mol-1、-161.0 J·mol-1·K-1,比ClO2氧化体系的热力学参数略高一些。水体共存无机离子和天然有机物的影响实验结果表明,相同环境因子对不同氧化消毒体系产生的影响差别很大。在Fe(Ⅵ)氧化反应体系中,起不同程度促进效应的共存因子有:NO3-、HCO3-、NH4+、Ca2+、Fe3+、CTAB和腐殖酸,起抑制作用的有Cl-、SDBS和Tween-80,同样SO42-、Mg2+对反应影响甚微,同时提出了各个环境因子发挥效应的作用机制。4.探讨了Fe(Ⅵ)氧化双氯芬酸的反应机理、毒性变化及TOC去除效果。根据UPLC-MS质谱图,结合双氯芬酸的结构特点和Fe(Ⅵ)的反应特性,推测出5种初级产物,反应由Fe(Ⅵ)直接亲电氧化为主导,·OH自由基贡献不大,主要反应途径包括母体物质及其中间产物的羟基取代反应和中间体自由基的偶联反应,形成的副产物主要有氯代酚类、醌类及其它二聚体形态。随着反应时间的延长,反应液的矿化程度逐渐提升,而毒性在反应初期稍有下降,然后随着双氯芬酸不断降解,毒性开始增大而后又缓慢减小,在双氯芬酸刚刚消失以后达到最大,说明双氯芬酸的初级降解产物氯代酚类衍生物对毒性贡献小,而中间体自由基形成的醌类二聚体的毒性最大。比较而言,由于Fe(Ⅵ)氧化体系中产生一些分子量更大的降解副产物,使其脱毒和矿化过程相对比ClO2要长一些。更多还原

【Abstract】 In recent years, diclofenac(DCF) is one of the most commonly used non-steroidal anti-inflammatory drugs and emerging micro-organic contaminants, which has been frequently detected with high levels in the aquatic environment. Researches have shown that traditional flocculation, precipitation and filtration cannot remove DCF efficiently because of its low biodegradability and limited elimination capacity,leading to significant emissions to drinking water disinfection process. As two sorts of new multifunctional water treatment reagents and oxidants, chlorine dioxide(ClO2) and ferrate(Fe(Ⅵ)) are widely used for the disinfection of relatively high quality water including groundwater, surface water and drinking water or used as preoxidation of wastewater before conventional disinfection process. They have been proved to be promising disinfectants to remove both inorganic and organic contaminants. However, due to poor mineralization of water treatment, research on organic pollutants removal as well as byproducts formation is critically important to address the safety concerns of drinking water treatment, since some byproducts may be of similar or even higher toxicity compared with their parent compounds.To both investigate the removal efficiency and reaction kinetics and elucidate degradation mechanism and toxicity variation, we select DCF as target compound and ClO2 and Fe(Ⅵ) as two typical disinfectants respectively to carry out our systematic study, which provide theoretical basis and technical support for practical application in drinking water treatment. The primary conclusions achieved in this work are as follows:1. The reaction kinetics, removal efficiency and influence factors on the degradation of DCF by aqueous ClO2 were investigated under simulated water disinfection conditions. The results showed that DCF could be rapidly and completely oxidized in the presence of an excess of ClO2. All the reactionsfollowed second order kinetic model and measured rate constant was 1.50×103 M-1·s-1 under the condition of pH 7.0 and 298 K. The reaction rate constants and degradation rates were obviously affected by the ClO2 concentration and reaction temperature instead of pH. The activation energy, enthalpy and entropy were7.87 kJ·mol-1、5.38 kJ·mol-1、-165.75 J·mol-1·K-1, respectively, which indicated that DCF-ClO2 reaction can occur under conventional drinking water treatment conditions. Base on the experiments results with the addition of inorganic salt or organic matter, different coexistent matters were found to play different roles in the DCF removal behavior. The presence of NO3-, Cl-, Br-, Ca2+, Fe3+ or surfactant CTAB optimized and accelerated the degradation of DCF by ClO2 to a certain extent, while the inhibitory effect were observed instead in the presence of NH4+, NO2-, I-, Fe2+, humic acid and surfactant SDBS, Tween-80, the addition of SO42- and Mg2+ had little impact on the removal of DCF. Furthermore the mechanism of these influences were analyzed.2. The reaction mechanism, toxicity variation and TOC removal efficiency were elucidated during the oxidation of DCF by ClO2. Nine byproducts were identified by UPLC-MS and 1H-NMR. Three main reaction pathways were based on initial decarboxylation of DCF on the aliphatic chain, hydroxylation and chlorination of the phenylacetic acid moiety at the C-4 position. DCF was oxidized by Cl O2 dominantly and by O2·- partially. With the increase of ClO2 dosage, TOC removal efficiency continuously increased,but the inhibition of luminescent bacteria vibrio fischeri initially increased and subsequently decreased,suggested that more toxic intermediates were formed. It was inferred that toxicity was mainly contributed by phenolic derivative and aldehyde intermediate.3. The reaction kinetics, removal efficiency and influence factors on the oxidation of DCF by Fe(Ⅵ)were investigated. The study demonstrated that ferrate could be applied to effectively remove DCF in the disinfection of potable water. The reaction between DCF and Fe(Ⅵ) followed second-order kinetics. Thevalue of rate constant was measured to be 5.04 M-1·s-1, at pH 9.0 and 298 K, which is lower than that of ClO2. The concentration of Fe(Ⅵ), pH and temperature exhibited significant influences on the DCF-Fe(Ⅵ)reactivity. The rate constants and degradation rates gradually decreased as pH was increased from 7.0 to11.0, and the species-specific rate constants were 16.8 M-1·s-1 for HFeO4- and 3.61 M-1·s-1 for FeO42-respectively. Ea, △H and △S were determined to be 23.3 kJ·mol-1, 20.9 kJ·mol-1,-161.0 J·mol-1·K-1,respectively. The experiments of coexisting substances in nature water showed that the same environmental factor has different effect results on two oxidation reaction system. In the Fe(Ⅵ) system, the presence of NO3-, HCO3-, NH4+, Ca2+, Fe3+, CTAB and humic acid clearly initiated its promotion, whereas the presence of Cl-, SDBS and Tween-80 had some inhibition effect on the removal of DCF, the addition of SO42- and Mg2+ still conveyed little influences on the reaction. Furthermore, the causal effects of the relevant factors were interpreted.4. The reaction mechanism, toxicity variation and TOC removal efficiency were explored during the Fe(Ⅵ) oxidation process. Five primary products were identified by UPLC-MS combined with the structure characteristic of DCF and reactivity properties of Fe(Ⅵ). Fe(Ⅵ) rather than ·OH radical plays a dominant role during the oxidation process. The reaction mechanisms were proposed to be hydroxylation of DCF and degradation products and coupling reaction of organic radical intermidates. DCF oxidation occurred an the phenol moiety and yielded chlorophenol, quinine intermediates and other organic dimmers. As the reaction time was prolonged, the mineralization of solution was gradually improved, while there was a slight decrease of inhibition rate during the initial reaction period. Subsequently, the overall toxicity began to increase rapidly and then decreased slowly, reaching a maximum inhibition rate when DCF had just completely disappeared. These results suggested that higher concentrations of chlorophenol derivatives did not yield appreciable effect on the overall toxicity, relative to quinine dimmer. In contrast, the detoxicationand mineralization process in the Fe(Ⅵ) oxidation system was longer than in the ClO2 oxidation system due to the formation of higher molecular weight of disinfection byproducts.更多还原