【作者】 相欣奕；

【导师】 郑怀礼；

【作者基本信息】 重庆大学 ， 市政工程， 2013， 博士

【摘要】 从有机物降解过程看，其本质而言是氧化过程。应用各种氧化技术在较短时间里将难降解、毒性大的有机污染物完全无害化、不产生二次污染，己成为当前环境污染治理的热点之一。近年来把氧化技术应用于难降解有机污染物的研究极为活跃，其有效性得以验证，但就氧化降解机理研究不足。在当前已开展的相关研究发表文献中，对氧化降解机理与历程，绝大多数停留在推测阶段。涉及高级氧化法中自由基参与反应的方式、中间产物的生成等关键信息，目前少有报道。论文选题是环境氧化技术对典型有机污染物降解机理与应用研究。主要完成三个目标：①借助EC-MS技术以及紫外光解结合质谱分析揭示典型有机污染物氧化降解历程与机理；②氧化技术用于实际的典型有机废水处理的有效性确认；③对前期完成水溶性染料模拟废水高级氧化降解历程的重新分析。氧化机理实验包含基于EC-MS的氯四环素氧化降解实验以及基于质谱的氯四环素紫外光解历程分析两个阶段。就EC-MS装置展开的氯四环素电化学氧化降解实验而言：pH=3.0体系之中，CTC出现明显降解趋势的时间点对应的电压为1120mV；pH=6.8体系之中，CTC出现明显降解趋势的时间点对应的电压为1264mV；pH=10.0体系之中，CTC出现明显降解趋势的时间点对应的电压为1510mV。在pH=3.0体系中，EC中电压为1822mV时开始产生羟基自由基；在pH=6.8体系中，EC中电压为1948mV时开始产生羟基自由基；在pH=10.0体系中，EC中电压为2020mV时开始产生羟基自由基。就产物m/z=495正离子峰高值来看，pH=3.0体系中出现的m/z=495正离子峰强度高值为1.4×10⁶，pH=6.8体系为6.0×10⁵，pH=10.0体系为10.0×10⁵，表明在酸性体系中羟基自由基生成浓度最大，与EC-MS实验所确定的CTC在酸性条件下易于氧化降解的特征相对应，构成羟基自由基的进攻是CTC电氧化降解初始步骤的证据。光解实验采用以中压汞灯反应装置为光源，甲醇与纯水作为溶剂，醋酸铵作为缓冲剂的CTC溶液体系光解实验，并考察了零价铁、氧化锌和二价铁离子所发挥的作用。氯四环素的紫外光解氧化实验结论如下：CTC在酸性条件下最稳定，中性体系中次之，在碱性体系中光降解稳定性最差。零价铁的加入对pH=3.0的体系中CTC的降解产生明显促进作用，原因在于零价铁被氧化成为亚铁离子和铁离子，与体系中光生羟基自由基共同构成光助Fenton体系发挥功效。在pH=3.0的体系中引入0.005mmol/L浓度的Fe（II）离子，对于这一体系CTC紫外光解产生显著促进作用，此时也会出现产物正离子峰m/z=532。氧化锌对pH=10.0和6.8体系中的CTC紫外光解发挥显著促进作用，实验并未发现锐钛型二氧化钛发挥明显催化效果。提供了通过质谱图识别出的三种pH体系逐时光解产物离子峰信息。就电化学氧化降解和光氧化降解机理而言：酸性体系中CTC电氧化降解初始步骤在于羟基自由基进攻CTC分子结构中的苯环，使其活化并逐步降解；中性和碱性体系中CTC电氧化降解初始步骤则在于羟基自由基和超氧自由基的共同作用。酸性体系中CTC的紫外光解，在于超氧自由基作用导致；中性体系中CTC的紫外光解，仅识别出羟基自由基的攻击合成产物；而碱性体系中CTC的紫外光解，则由羟基自由基和超氧自由基共同作用导致。在亚铁离子引入pH=3.0体系的CTC光降解的历程，首先是CTC与亚铁络合脱除两个氢生成产物（532=479+56-2），这一络合物降解是通过体系中因光照产生的超氧自由基作用发生。ZnO对CTC在pH=6.8的体系中的光催化氧化降解起到促进作用，此时CTC降解经历步骤如下：CTC脱氯，生成TC（对应m/z=445）；CTC与缓慢释放进入溶液中的锌离子产生络合；CTC受系统中生成的超氧自由基攻击，产生加成产物。氧化技术应用实验是对环境氧化法有效性的确认，Fenton技术和铁炭内电解法处理垃圾渗滤液实验得到的结果如下：Fenton氧化降解垃圾渗滤液实验中， pH=3.0，Fe²⁺/H₂O₂比例为1:30时，垃圾渗滤液COD的去除效果可达到40%⁵0%的范围，U_V254的去除率可达到30⁴0%。铁-炭内电解法处理垃圾渗滤液实验中，流过式铁炭填充柱对COD、浊度的去除率优于铁炭混合浸泡法。流过式铁炭填充柱对COD的去除率可达60%，浊度去除率可达94%。氧化技术应用部分还包括对前期完成水溶性染料模拟废水高级氧化降解历程的重新分析。论文通过针对实际产生的高浓度废水垃圾渗滤液、简化的模拟废水染料水溶液，以及氯四环素甲醇水溶液这一适合于质谱仪器分析的体系，分别采用Fenton氧化法、铁炭内电解法、光助Fenton法、EC电化学实验装置耦合有机质谱分析法以及紫外光解法等氧化还原及高级氧化技术与实验方法，对环境氧化技术展开了机理与应用研究，以期为适合于有机污染物处理的新型高效氧化技术的设计与开发提供依据。更多还原

【Abstract】 Based on the processes of organic pollutants degradation, it is composed ofoxidation reactions. Oxidation technology can be used in treatment of persistent andtoxic organic pollutants in quite short period with minimized secondly pollution, whichmakes it a focus in recent environmental researches. Because the targeted pollutants canbe destroyed completely, advanced oxidation processes are also namely as destructivetechnology, which have found more and more wide applications currently.Experimental researches in this study can be described as three stages:①powerfulEC-MS technology was used to look into the details in the complete organic pollutantsoxidative degradation and the photocatalytic degradation processes;②the effectivenessof oxidation processes was confirmed by applying Fenton’s reaction and iron-carbonelectrolysis technology in landfill leachate treatment;③mechanisms of environmentaloxidation processes were reviewed and probed into based on previous water-solubledyes oxidative degradation data.In part I experiments, the results are as follows:There are two series of experiments, namely oxidative degradation of two typicalantibiotics based on EC-MS technology, and ultraviolet degradation of chlortetracyclineand products identification with organic mass spectrometer.Taking advantage of EC-MS technology, oxidative degradation tendencies ofchlortetracycline in three pH conditions, namely pH=3.0,6.8and10.0were compared,and possible derivative products of chlortetracycline in natural environment wereidentified. Oxidative degradation products of chlortetracycline with the electric potentialrising from0to+2500mV were identified with organic mass spectrometer in threedifferent pH conditions. More than10product positive ion peaks are of interest, some ofwhich have got their possible molecular formulas. In pH=3.0system，when the voltagein EC reached1120mV, CTC showed the tendency of degradation; in pH=6.8system,when the voltage in EC reached1264mV, CTC showed the tendency of degradation; inpH=10.0system, when the voltage in EC reached1510mV, CTC showed the tendencyof degradation. In pH=3.0system，when the voltage in EC reached1822mV, hydroxylradicals were generated; in pH=6.8system，when the voltage in EC reached1948mV,hydroxyl radicals were generated; in pH=10.0system，when the voltage in EC reached2020mV, hydroxyl radicals were generated. As for the production of product m/z=495, the highest ion intensity of this ion in pH=3.0was1.4×10⁶; in pH=6.8system, it was6.0×10⁵and in pH=10.0system, it was10.0×10⁵. It was believed as an evident thatelectrical chemistry oxidative degradation of CTC was initiated by the attacking fromhydroxyl radicals.In UV degradation experiments, middle-pressure immersion UV lamp （TQ150,150W） was used as the core of the UV reactor, provided with quartz burner and quartzcooling water jacket. The reaction system was composed of methanol and pure water, assolvent, and ammonium acetate as buffer agent, chlortetracycline as the UV degradationtarget. In addition to the investigation on the UV degradation processes of CTC in3different pH conditions, effects of zero-valent iron, zinc oxide, titanium dioxide andFe（II） were studied. Based on the result, it was found in acidic system, CTC is moststable under UV radiation, while in alkaline condition, CTC is most active to degrade.Zero valent iron can promote the UV degradation of CTC in pH=3.0system, and thepositive ion peak m/z=534of the complex of iron ion with CTC was identified. It wasbelieved that in acid system, zero valent iron was transferred into Fe（II） and Fe（III） ions,which would contribute as the catalytic agents in UV-Fenton’s system. The othernecessary part of Fenton’s reaction is hydroperoxide, which was produced by UVirradiation in the system. Although methanol was reported as a kind of free radicalquenching agent, but UV radiation-induced hydroperoxide generation is so rapid thatthe Fenton’s reaction can take place. In neutral system （pH=6.8）, zero valent iron canhardly be transferred into Fe（II） or Fe（III） ions into the solution and there was noevidence that zero valent iron itself can not promote the UV degradation of CTC. Inaddition, there was no positive ion peak m/z=534of the complex of iron ion with CTCidentified.In pH=3.0system, introduction of0.1mmol/L Fe（II） can promote the UVdegradation of CTC obviously, and also the positive ion peak m/z=534of the complexof iron ion with CTC identified. Zinc oxide exerted different effects in different systemsin UV degradation of CTC. In pH=3.0system, rapid chemical reaction took placebetween zinc oxide and CTC. In pH=10.0and pH=6.8systems, zinc oxide can promoteUV degradation of CTC obviously. Several positive ion peaks of the products wereidentified, including two kinds of complex of CTC with zinc ions.For application of Fenton’s process in landfill leachate treatment, when pH=3andFe²⁺/H₂O₂molar concentration ratio was1:30, COD remoal of landfill leachate was inthe range of40%⁵0%and UV254removal was in the range of30⁴0%. For application of iron-carbon electrolysis process in landfill leachate treatment,effect of flow-in iron-carbon column is better than mixed immersion of iron scraps andcarbon grapes for the remoal of COD and turbudity. In the experiment conditions,COD removal of landfill leachate was60%and turbudity remoal was as high as94%with flow-in iron-carbon column even in weakly acidic condition.Experiment results listed in part III experiment was carried out previously andextracted from published thesises of the candidate herself, based on which, the pathwayand mechanisms were reconsidered to provide reliable basis for effective oxidationtechnology development suitable for organic pollutants treatment.In conclusion, in this study, real landfill leachate of high-concentration organicpollutants, simplified water-soluble dyes water solutions and chlortetracyclinemethanol-water solution were selected as the research systems, Fenton’s oxidationprocess, iron-carbon internal electrolysis method, UV-Fenton process, EC-MStechnology and UV reactor coupled with organic mass spectrometer were used foroxidative degradation research. The research covered the preliminary determination oftreatment efficiency to the reckoning on reaction steps, to the identification of productsand intermediate products in the oxidative degradation processes by the powerful MStechnology. Wishing it can make contribution to new flexible technologies developmentfor the treatment of distributed waste water.更多还原