不同氯酚对催化剂氧化降解的响应及机制

发布时间：2018-03-17 08:50

本文选题：Fe-Cu-柱撑粘土(Fe-Cu-PILC)　切入点：氯酚　出处：《西北农林科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：氯酚是工业废水中一种较为常见的有机污染物,具有高毒性和难生物降解性,其消解一直是环境治理中的热点和难点。本文选用环保高效的催化湿式过氧化氢氧化法对氯酚进行催化氧化降解,而此方法的关键在于制备高效的催化剂。该研究通过共沉淀法制备了Fe-Cu-柱撑粘土(Fe-Cu-PILC)催化剂,并以单氯酚、二氯酚、三氯酚作为模式化合物,研究了氯酚中氯原子取代数目、取代位置对其降解动力学的影响,还研究了氯酚(CPs)氧化过程中H_2O_2,Cl~-,羟基自由基(·OH)和总有机碳(TOC)的浓度变化,此外,通过液相色谱-质谱(LC-MS)检测CPs氧化期间形成的中间体,并探讨了氯离子的存在对反应的影响,也基于费米分布函数对其降解动力学进行非线性拟合。该研究主要得出以下主要结论:(1)Fe-Cu-PILC/H_2O_2体系氯酚的氧化降解动力学可用一个基于费米函数的半经验模型拟合(R20.818),从而求得表观速率常数k和半衰期t*。据此,氯酚降解速率次序为3-CP3,5-DCP2,3-DCP3,4-DCP2,5-DCP4-CP2-CP2,4-DCP2,4,6-TCP2,6-DCP。(2)苯环氯原子取代位置、取代数目均会对氯酚降解产生影响:对于单氯酚,氯原子在芳环间位时,降解最容易,其次为对位,位于邻位时最难降解;对于二氯酚,间位氯原子取代越多,越容易降解,邻、对位氯原子越多,越难降解。但综合来看,相对于取代数目,氯原子取代位置占据更主要的影响作用:氯原子取代数目相同时,间位氯越多,降解越快,邻对位越多,降解越慢。(3)Fe-Cu-PILC/H_2O_2体系中,Cl~-的存在抑制了CPs氧化速率,其中tI从60.2延长到86.9 min,t1/2延长到33.8 min(从88.4到122.2 min)。但是抑制作用只能在邻位氯酚如2,6-DCP的氧化过程中发生,其中tI被延长到119.7 min(从233.8到353.5 min),而在间位或对位氯酚的氧化过程中几乎可以忽略不计。此外,Cl~-的存在不影响CPs的转化(脱氯和羟基化)和深度氧化(矿化)。也就是说,Cl~-的存在没有改变氧化路径,如LC-MS所证明的。Cl~-释放,H_2O_2分解,貽H形成和中间产物鉴定的多重指标表明,Cl~-对邻位氯酚氧化的抑制机制一方面主要是由于通过与H_2O_2竞争Fe(III)的络合抑制H_2O_2分解的限速步骤,另一方面是由于貽H被清除而形成·Cl2-。
[Abstract]:Chlorophenol is a common organic pollutant in industrial wastewater, which is highly toxic and difficult to biodegrade. The degradation of chlorophenol has been a hot and difficult point in environmental treatment. In this paper, the catalytic oxidation degradation of chlorophenol was carried out by catalytic wet hydrogen peroxide oxidation with environmental protection and high efficiency. The key point of this method is to prepare high efficient catalyst. Fe-Cu-pillared clay Fe-Cu-PILC catalyst was prepared by coprecipitation method, and the number of chlorine atoms substituted in chlorophenol was studied with monochlorophenol, dichlorophenol and trichlorophenol as model compounds. The effect of substitution position on the degradation kinetics was also studied. The concentration changes of H _ 2O _ 2Cl _ (-), hydroxyl radical (路OH) and total organic carbon (TOC) during the oxidation of CPs were also studied. In addition, the intermediates formed during the oxidation of CPs were detected by liquid chromatography-mass spectrometry (LC-MS). The influence of chloride ion on the reaction was also discussed. The main conclusions of this study are as follows: the oxidation kinetics of chlorophenol can be fitted by a semi-empirical model based on Fermi function, which can be used to simulate the degradation kinetics of chlorophenol in the system of FeCu-PILC / H _ 2O _ 2. And the apparent rate constant k and the half-life tr are obtained. The degradation rate of chlorophenol is in the order of 3-CP3N 5-DCP2N 4-DCP4-CP2-CP2-CP2-CP2-DCP2-O4-DCP2-DCP2-O4-DCP2-O4-DCP2-O4-DCP2-DCP2) the substitution position of benzene cyclic chlorine atoms, the number of substitutions will affect the degradation of chlorophenols: for mono-chlorophenols, the degradation of monochlorophenol is the easiest when the chlorine atom is in the aromatic ring, followed by the opposite position, and the most difficult to degrade at the adjacent position; For dichlorophenols, the more m-site chlorine atoms are substituted, the easier it is to degrade, and the more para-chlorine atoms are, the more difficult it is to degrade dichlorophenol, but, taken together, relative to the number of substitutions, When the number of chlorine atoms is the same, the degradation rate of CPs is inhibited by the presence of more chlorinated atoms, faster degradation, more adjacent sites, slower degradation, and lower degradation rate in Fe-Cu-PILC / H _ 2O _ 2 system. T I was prolonged from 60.2 to 86.9 min / 1 / 2 to 33.8 min (from 88.4 to 122.2 mins). Ti was extended to 119.7 mins (from 233.8 to 353.5 mins) and was negligible during the oxidation of chlorophenols in the meta or para-position. In addition, the presence of ti-did not affect the conversion (dechlorination and hydroxylation) and deep oxidation (mineralization) of CPs. It means that the presence of Cl- does not change the oxidation path. As proved by LC-MS, the multiple indexes of the decomposition, formation and identification of intermediate products indicate that the inhibition mechanism of the oxidation of o-chlorophenol is mainly due to the inhibition of the decomposition of H _ 2O _ 2 by the complexation with H _ 2O _ 2, and the limiting steps of the decomposition of H _ 2O _ St _ 2 by means of the complexation with H _ 2O _ 2. On the other hand, the formation of 路Cl2-.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703;O643.3

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