【作者】 李静；

【导师】 钟金魁；

【作者基本信息】 兰州交通大学 ， 环境科学， 2022， 硕士

【摘要】 近年来,随着造纸、印染、农药及医药等的迅速发展,生产中间体氯酚（CPs）类物质造成的水污染问题日趋严重,因此,其治理和修复是目前亟需解决的环境难题。在众多的水处理技术中,利用纳米零价铁的强还原性和Fenton技术的强氧化性处理CPs污染水体成为环境科学领域的研究热点。本文以磁性纳米Fe₃O₄负载的纳米零价铁（n ZVI）为催化剂,构建类Fenton体系对三种典型CPs（即,对氯苯酚（4-CP）、2,4-二氯苯酚（2,4-DCP）和2,4,6-三氯苯酚（2,4,6-TCP））的降解效果进行了研究,考察了影响CPs降解的关键因子,探究了CPs在Fe₃O₄-n ZV类Fenton体系中的降解机理和途径,为Fe₃O₄-n ZVI类Fenton体系处理CPs废水提供参考和依据。主要结论如下:1.扫描电子显微镜（SEM）和X射线能谱分析（EDS）表征结果表明Fe₃O₄-n ZVI粒径为纳米级（50～200nm）,颗粒呈球型以链状连接,元素组成中Fe和O的占比分别为64.27%和16.53%,为复合材料的主要构成元素。光电子能谱分析（XPS）和X射线衍射分析（XRD）的谱图中出现了明显的Fe₃O₄能谱特征峰,证实了Fe₃O₄的存在,n ZVI处于无定形状态。振动样品磁强度分析（VSM）证明Fe₃O₄-n ZVI具有较好的磁分离性能,可进行磁回收利用。2.批平衡实验结果表明,（1）不同纳米材料和体系对CPs的去除能力存在明显差异,单独的H₂O₂体系对CPs的表观降解率最低,各体系对CPs的表观降解率顺序是H₂O₂<Fe₃O₄<n ZVI<Fe₃O₄-n ZVI<Fe₃O₄-H₂O₂<n ZVI-H₂O₂<Fe₃O₄-n ZVI-H₂O₂;（2）在一定实验控制条件范围内,增大H₂O₂浓度可有效提高CPs的表观降解率,当浓度超过该范围（0～15mmol/L）,CPs的表观降解率随H₂O₂浓度的增大而减小;（3）CPs的表观降解率随Fe₃O₄-n ZVI投加量的增大而增大,但当其投加量超过0.6g/L时,CPs的表观降解率反而会降低;（4）溶液初始p H对CPs的表观降解率影响非常明显,降低体系p H可有效提高CPs的表观降解率,但当p H<3时,CPs的表观降解率反而出现下降趋势;（5）CPs的表观降解率也受其初始浓度影响,即增加CPs的初始浓度,其表观降解率出现下降;（6）反应温度似乎对CPs的表观降解率影响并不明显。3.淬灭实验、动力学拟合和质谱结果表明Fe₃O₄-n ZVI类Fenton体系对CPs的降解中·OH氧化占主导地位,降解过程符合拟一级动力学方程,降解机理包括氯的取代和亲电加成反应。即,Fe₃O₄-n ZVI类Fenton体系中多氯酚转化单氯酚,单氯酚再进一步转化为酚类化合物,酚类化合物再经氧化为醌,最后开环转变为小分子酸,直至成CO₂和H₂O。更多还原

【Abstract】 In recent years,with the rapid development of papermaking,printing and dyeing,pesticides and pharmaceuticals,the problem of water pollution caused by the production of intermediate chlorophenols（CPs）has become increasingly serious.Among the many water treatment technologies,the use of the strong reducibility of nano-zero valent iron and the strong oxidation of Fenton technology to treat CPs-contaminated water has become a research hotspot in the field of environmental science.In this paper,magnetic nano-Fe₃O₄-supported nano-zero-valent iron（n ZVI）was used as a catalyst to construct a Fenton-like system for three typical CPs(i.e.,p-chlorophenol（4-CP）,2,4-dichlorophenol（2,4-DCP）and 2,4,6-trichlorophenol（2,4,6-TCP）were studied,the key factors affecting the degradation of CPs were investigated,and the degradation of CPs in Fe₃O₄-n ZVI-like Fenton system was investigated.The degradation mechanism and pathway provide reference and basis for the treatment of CPs wastewater by Fe₃O₄-n ZV-like Fenton system.The main results and conclusions are as follows:1.The characterization results of scanning electron microscope（SEM）and energy dispersive X-ray analysis（EDS）show that Fe₃O₄-n ZVI has a nanoscale particle size（50～200nm）,and the particles are spherical and connected in chains.The proportions are 64.27%and 16.53%respectively,which are the main constituent elements of composite materials.The characteristic peaks of Fe₃O₄ energy spectrum appeared in the spectra of photoelectron spectroscopy（XPS）and X-ray diffraction（XRD）analysis,which confirmed the existence of Fe₃O₄ and n ZVI was in an amorphous state.Vibration sample magnetic strength analysis（VSM）proved that Fe₃O₄-n ZVI has good magnetic separation performance and can be used for magnetic recycling.2.The results of batch equilibrium experiments show that（1）there are significant differences in the removal ability of different nanomaterials and systems for CPs.The apparent degradation rate of CPs by a single H₂O₂ system is the lowest,and the apparent degradation rate of CPs by each system is in the order of H₂O₂<Fe₃O₄<n ZVI<Fe₃O₄-n ZVI<Fe₃O₄-H₂O₂<n ZVI-H₂O₂<Fe₃O₄-n ZVI-H₂O₂;（2）Within a certain range of experimental control conditions,increasing the concentration of H₂O₂ can effectively improve the apparent degradation rate of CPs.Above this range（0～15mmol/L）,the apparent degradation rate of CPs decreased with the increase of H₂O₂ concentration;（3）the apparent degradation rate of CPs increased with the increase of Fe₃O₄-n ZVI dosage,However,when the dosage exceeds 0.6 g/L,the apparent degradation rate of CPs will decrease;（4）The initial p H of the solution has a very significant effect on the apparent degradation rate of CPs,and reducing the p H of the system can effectively improve the apparent degradation rate of CPs.However,when p H<3,the apparent degradation rate of CPs showed a downward trend instead;（5）The apparent degradation rate of CPs was also affected by its initial concentration,that is,increasing the initial concentration of CPs,its apparent degradation rate appeared（6）The reaction temperature does not seem to have a significant effect on the apparent degradation rate of CPs.3.The results of quenching experiments,kinetic fitting and mass spectrometry indicated that·OH oxidation was dominant in the degradation of CPs by Fe₃O₄-n ZVI-like Fenton system.The process conformed to the pseudo-first-order kinetic equation.The mechanism included chlorine substitution and electrophilic reaction.That is,in the Fe₃O₄-n ZVI-like Fenton system,polychlorophenols are converted into monochlorophenols,and monochlorophenols are further converted into phenolic compounds,which are then oxidized to quinones,and finally converted into small molecular acids by ring-opening,until CO₂ and H₂O.更多还原