【作者】 丛燕青；

【导师】 吴祖成； 谭天恩；

【作者基本信息】 浙江大学 ， 环境工程， 2005， 博士

【摘要】 氯酚类芳香化合物毒性大、难生物降解,具有“三致”效应和遗传毒性,在环境中长期残留、降解周期长,被美国环境保护局列为优先控制污染物。本文从获取氯酚系列化合物的分子结构信息以期指导其治理过程着手,考察电化学作用下的降解行为,开发出电催化激活分子氧工艺、光助电催化氧化工艺和活性炭载钯电化学处理工艺,以分布最广的水和土壤典型环境进行净化修复研究,为其治理提供基础数据和理论依据。 计算了全系列氯酚化合物的分子结构参数和能量,基于C-Cl、C-O和O-H的键长、键角及分子内的氢键与氯取代基的位置,排序了氯酚类化合物稳定性和pKa值,化合物结构的稳定性与降解的关系和pKa对迁移率贡献应用于实验的设计。借助UV-VIS光谱、Raman光谱、HPLC色谱等现代分析技术,考察了氯酚的电化学降解行为,证实了在电化学降解过程中4-氯酚的C-Cl键发生断裂和破环反应。电化学氧化降解中C-Cl键断裂是羟基攻击苯环发生亲电加成反应的结果,继而提出还原脱氯和氧化降解结合的工艺。 开发了电催化激活氧气降解氯酚工艺。常温常压下不活泼的氧气分子在电催化作用下被激活,产生HO^·、HO₂^·等强氧化性活性物质。对氯酚和毒性大的中间产物苯醌等去除效果显著,氧气激活增强因子为110%。电流密度、曝氧或空气量、pH值、温度等因素对电催化激活分子氧有不同程度的影响。电催化激活分子氧的工艺具有广泛适用性,对酸性或碱性的氯酚废水,不需稀释或中和调节而直接处理,50mgL^-1的降解率240min时达到95%以上。实验还发现废水的浓度在很大的范围均有高的降解速率,增加了40倍的氯酚初始浓度高达2000mgL^-1时其仍有80%,同时其中间产物如苯醌亦降解迅速。基于此的初步工程设计可用于工业废水治理。 发展了光助强化电催化氧化工艺处理氯酚,将紫外光引入电催化反应器,光电结合协同作用明显,增强因子达到108%。当操作条件相同时,在120分钟的处理时间内,氯酚的去除效率:光助电催化激活氧气>光助电催化>电催化激活氧气>电催化。光助电催化工艺适合处理浓度小于1000mgL^-1的氯酚废水,对pH值在3-9间的氯酚废水都能取得较好的处理效果。光电结合能促进羟基自由基的氧化作用,紫外光的引入促进了对电催化副产物氧气的利用。氯酚降解的主要产物与电催化激活氧气过程相似,降解动力学符合表观一级反应过程。 制备了载钯活性炭催化剂用于氯酚废水处理,其吸附等温曲线遵循Freundlich等温式。实验结果表明载钯促进氯酚的去除,氢气对载钯催化剂的脱氯效果起着非常关键的作用。载钯活性炭电化学处理工艺对氯酚的去除作用主要包括三方面:（1）活性炭的吸附;（2）活性炭微电极表面钯还原脱氯;（3）电极表面上的降解矿化。该工艺采用还原作用脱除氯酚污染物中的氯取代基,使氯离子从苯酚母体上解离,苯酚进一步降解直至更多还原

【Abstract】 Chlorophenols （CPs）, having high toxicity, biorefractory, bioaccumulation and carcinogenic potential, are widely found in the environment and are significant contaminants at many sites selected for cleanup on the USEPA top priority toxic pollutants list. There is need to treat such contaminants in concerning of environmental protection. In present work, various electrochemical methods such as electrocatalytic activation of dioxygen, photo-assisted electrocatalysis, and electrochemical dechlorination by activated carbon loaded palladium, were developed to treat and remediate water and soil contaminated by chlorophenols.Calculation of molecular structure and properties of the whole chlorophenols series by applying Gaussian’98 software were carried out to arrange and assist experiments design based on their stabilities and pKa values. Electrochemical degradation behaviors of chlorophenols were systematically investigated by employing analytical techniques of UV-VIS, Raman spectroscopy and HPLC. For electrochemical degradation of 4-CP, the C-Cl bond was broken and chlorine ion was taken away from the benzene ring as a result of electrophilic addition reaction of hydroxyl radical. The combination technologies of reduction dechlorination and oxidation degradation were proposed.Electrocatalytic activation of dioxygen for chlorophenol degradation was studied. At ambient temperature and atmosphere pressure, dioxygen can be activated to generate stronger oxidants such as HO and HO2 under the electrocatalysis. The process of activated dioxygen with electrocatalysis can significantly improve the degradation of chlorophenol and its intermediate. The promoting factor for 4-CP degradation was 110%. Operational parameters can affect the activation of dioxygen in electrochemical process such as current density, sparged dioxygen rate, pH, and temperature. By applying the technique, acid/alkali and enriched wastewater can be treated without necessary pretreatment with efficiency over 95% for a 240 min treatment of a 50 mg L^-1 concentration. It was found that removal rate of chlorophenol could be 80% for high concentration of 2000 mg L^-1, 40 times as normal, and highly descended for its intermediate of benzoquinone. The preliminary systematic design and economic validity of the technology were analyzed.Photo-assited electrocatalysis technology was developed. Synergetic effects of the combined process were obvious and the promoting factor was 108%. Given the same operating conditions and reaction time, the removal rate of 4-CP followed the sequence: photo-assited electrocatalysis activation of dioxygen > photo-assited electrocatalysis > electrocatalysis activation of dioxygen > electrocatalysis. Photo -assited electrocatalysis technology had good efficiency on the lower concentration chlorophenol wastewater (less than 1000 mg L^-1). The combination of photocatalysis and electrocatalysis could enhance the更多还原