【作者】 孟亚锋；

【导师】 汪大翚；

【作者基本信息】 浙江大学 ， 环境工程， 2010， 博士

【摘要】 四氯化碳是一种被广泛应用的有机氯化物,化学性质稳定,具有生物毒性,在自然环境能够长期稳定地存在,严重污染了土壤和地下水,对生态环境造成长期的危害。本文以零价铁还原降解四氯化碳,分别采用表面活性剂负载、过渡金属催化和超声辅助等方法提高零价铁还原降解效率,并对四氯化碳实际工业废水进行中试。第一章和第二章叙述了四氯化碳来源、性质及对环境危害,并总结了各种传统处理有机氯化物的方法,零价铁还原处理有机氯化物技术应用现状和存在的问题,并表明本文的研究目的和意义。第三章介绍了实验仪器、所用试剂,以及各处理方法的实验方法和分析方法。第四章采用零价铁还原处理四氯化碳,得出的结论主要有：1)零价铁对水中四氯化碳有较好脱氯效果,在零价铁投加量10g/L,四氯化碳初始浓度20mg/L, pH7.0时,280min四氯化碳降解效率为86.1%。影响零价铁还原效果的因素主要有：投加量、反应温度和pH等。加大投加量和反应温度都能促进脱氯反应,pH对降解效率影响比较大,酸性条件有利于反应进行。四氯化碳降解符合一级反应动力学,在零价铁作用下转变成氯仿,氯仿继续脱氯最终变成二氯甲烷。2)加入硫酸盐与Fe2+和铁化合物形成绿铁锈,抑制铁表面钝化,有利于还原脱氯。分别采用两种阳离子和阴离子表面活性剂负载零价铁,结果表明两种阳离子表面活性剂(十六烷基三甲基溴化铵(CTAB)和溴代十六烷基吡啶(CPB))的负载浓度在临界胶束浓度以下时均可以增强铁脱氯效果,反应速率常数可以提高81%(CTAB)和130%(CPB),负载两种阴离子表面活性剂反而不利于零价铁还原脱氯。第五章分别采用Ni/Fe和Pd/Fe二元双金属降解四氯化碳,考察了四氯化碳影响因素和脱氯效率,并对动力学和反应产物进行分析。与零价铁相比,Ni/Fe和Pd/Fe具有更强的还原降解四氯化碳的能力,90分钟脱氯反应后,初始浓度20mg/L的四氯化碳在Ni/Fe体系下降解效率为92.8%,而Pd/Fe在60分钟反应四氯化碳降解效率为95.7%。影响Ni/Fe和Pd/Fe还原脱氯的主要因素有：Ni和Pd含量、投加量、反应温度和pH等。结果表明Ni和Pd含量增加、提高Ni/Fe和Pd/Fe投加量有利于四氯化碳降解,四氯化碳初始浓度对脱氯效果影响很小,pH在弱酸性条件下有利于脱氯反应,Ni/Fe和Pd/Fe降解四氯化碳的表观活化能分别为6.12 kJ/mol和3.95kJ/mol kJ/mol。Ni/Fe降解四氯化碳的产物主要是氯仿和二氯甲烷,Pd/Fe降解四氯化碳的产物主要是氯仿和二氯甲烷和甲烷。第六章利用超声辅助零价铁降解四氯化碳,主要影响因素有：超声声强、零价铁投加量和pH等。结果表明,超声和零价铁联合有明显协同作用,在最佳条件下,36min四氯化碳降解效果达到91.2%。产生这种协同作用的原因：超声空化可以去除金属表面形成的钝化,活化了金属表面,同时强化了界面间的化学反应和传质过程,超声的存在使得超声／零价铁体系保持了较低的pH环境也有利于零价铁的还原脱氯。第七章为零价铁还原处理四氯化碳废水工程中试,把零价铁处理四氯化碳技术推向工程实际应用。结果表明采用零价铁还原和电石渣絮凝工艺有效解决四氯化碳工业废水处理难题,铁粉在流化反应器中处于流化状态可有效与废水接触,防止了铁粉板结和堵塞。在实际废水pH为2-2.5条件下,连续进水时,投加量宜为2kg/t铁粉,当四氯化碳浓度在5-25 mg／L之间,还原出水浓度在1-5 mg／L。后续电石渣中和调pH值在7-9,其絮凝进一步去除水中的四氯化碳,出水浓度低于1 mg/L。更多还原

【Abstract】 As a kind of widely used organic chloride, chlorinated hydrocarbon has a stable chemical property and biological toxicity and can exist steadily in the natural environment for a long time. It seriously pollutes soils and groundwater and does great harm to the ecological environment. The reductive degradation of chlorinated hydrocarbon with zero-valent iron was investigated in this paper. The study was intended to enhance the degradation rate of the carbon tetrachloride with zero-valent iron by the application of surfactant load, transition metal catalysis and ultrasonic assistance. Pilot test of real industrial wastewater polluted by chlorinated hydrocarbon was also conducted in the experiment.Chapte 1 and Chapter 2 mainly dealt with the source, properties of chlorinated hydrocarbon and its harm to environment. Various conventional processing methods of organic chloride were introduced. The current situation and existing problems of the application of reductive treatment of chlorinated hydrocarbon with zero-valent iron were summarized. The aim and significance of the present study were also put forward in the first two chapters.Experiment instrument, reagent used and the experiment and analysis methods of various processing methods were introduced in Chapter 3.The reducting treatment of chlorinated hydrocarbon with zero-valent iron was studied in Chapte 4. The results showed that 1) Zero-valent iron had a good dechlorination performance on the chlorinated hydrocarbon in water. With the dosing quantity of carbon tetrachloride being lOg/L, initial concentration being 20mg/L, and pH valueof 7.0, the degradation rate of 280min chlorinated hydrocarbon reached to 86.1%. The effect of degradation was influenced by dosing quantity, reaction temperature and pH value. The dosing quantity and reaction temperature could enhance the dechlorination reaction, while pH value. had great infuence on the degradation efficiency and acdity condition was favorable for the reaction. The degradation of carbon tetrachloride followed first order kinetics. Under the influence of zero-valent iron, carbon tetrachloride transformed into chloroform, and then chloroform became dichloromethane.2) When sulfate and Fe2+ iron compounds were adding, green rust formed, which inhibited the passivation of iron surface and was favoralbe to the reductive dechlorination. Two kinds of cationic and anionic surfactants were used respectively to load the zero-valent iron, and the results showed that the cationic surfactants (CTAB and CPB) could enhance the effect of dechlorination when the loading concentration was under critical micelle concentration, and the reaction rate constant could increase by 81% (CTA) and 130% (CPB). While the anionic surfactants were unfavorable to the reductive dechlorination with zero-valent iron.In Chapter 5, the binary bimetal Ni/Fe and Pd/Fe were used to degrade the chlorinated hydrocarbon. The influencing factors and dechlorination efficiency of chlorinated hydrocarbon were investigated and the kinetics and reaction products were analyzed. Compared with zero-valent iron, Ni/Fe and Pd/Fe had better capacity of reductive degradation of chlorinated hydrocarbon. After 90 minutes, the dechlorination efficiency of chlorinated hydrocarbon in the Ni/Fe system was 92.8% when the initial concentration was 20 mg/L. And in the Pd/Fe system, dechlorination efficiency of chlorinated hydrocarbon was 95.7% after 6 minutes. The main factors influencing the reductive dechlorination were: content of Ni and Pd, dosing quantity, reaction temperature and pH value. It was found that the increase of the content and dosing quantity of Ni and Pd was favoralbe to the degradation of chlorinated hydrocarbon. The initial concentration of chlorinated hydrocarbon had little effect on the dechlorination efficiency. Under weak acidic condition, pH value could be favorable to the degradation. The apparent activation energy of Ni/Fe and Pd/Fe were 6.12kJ/mol and 3.95kJ/mol respectively. The degradation products of chlorinated hydrocarbon by Ni/Fe were mainly chloroform and dichloromethane, and the degradation products by Pd/Fe were mainly chloroform and dichloromethane and methane.In Chapter 6, ultrasonic-assisted degradation of chlorinated hydrocarbon with zero-valent iron was studied. The main influencing factors were:ultrasonic power, dosing quantity of zero-valent iron and pH value. The results revealed that the combination of ultrasound and zero-valent iron had obvious synergistic effect. Under optimum conditions, the 36min dechlorination efficiency of chlorinated hydrocarbon reached to 91.2%. The reasons for the synergistic effect were as follows:The ultrasonic cavitation could remove the passive and active metal surface, and meanwhile it enhanced the chemical reaction and mass transfer process interface between. Due to the ultrasound, the ultrasonic/iron system could maintain a lower pH value, which was helpful to the reductive dechlorination by zero-valent iron.The pilot test of reductive treatment of chlorinated hydrocarbon with zero-valent iron in wastewater treatment was investigated in Chapter 7, with the aim of promoting the practical engineering application of the degradation of chlorinated hydrocarbon with zero-valent iron. The results revealed that the degradation of chlorinated hydrocarbon with zero-valent iron and flocculation process by carbide slag could solve the problems in the treatment of industrial wastedwater. When the fluidized reactor of iron powder was under flocculation process, the iron powder could have effective exposure to the wastewater, which avoided the iron powder hardening and blocking. When the pH value in real wastewater was between 2-2.5, under continuous influent,2kg/t iron powder was suitable. When the concentration of chlorinated hydrocarbon was between 5-25 mg/L, the reduction effluent concentration was 1-5 mg/L. When subsequent carbide slag pH value was 7-9, the flocculation could remove the chlorinated hydrocarbon in water with the effluent concentration below 1 mg/L.更多还原