气体扩散阴极法降解水中苯酚和2,4-二氯苯酚的研究

发布时间：2018-01-02 06:24

  本文关键词：气体扩散阴极法降解水中苯酚和2,4-二氯苯酚的研究　出处：《哈尔滨工业大学》2015年硕士论文　论文类型：学位论文

  更多相关文章： 气体扩散阴极 降解 过氧化氢 中间产物 循环伏安法

【摘要】：近些年来,在电化学技术领域,环境研究者进行了广泛地研究。目前,一种新型的三相电极—气体扩散阴极,在阴极原位产生H2O2等强氧化性中间产物催化去除有机物和阴极电催化还原脱卤方面正备受关注。本论文研究制备了一种高效的气体扩散电极,该电极由防水透气层(气相层)、金属导电网(固相层)、催化层(液相层)组合而成,并直接以空气作为氧源,通过对苯酚、2,4-二氯苯酚的降解,建立了气体扩散阴极催化处理工艺体系,研究了改变电极运行条件对有机物降解的影响,并结合表征和电化学方法分析了气体扩散阴极法对苯酚、2,4-二氯苯酚的降解机理。考察了气体扩散阴极对苯酚降解的影响,并进行了表观动力学分析和钛网重复性能测试。结果表明,气体扩散阴极法降解苯酚的最佳条件:电流密度80 m A/cm2,电解质浓度0.2 mol/L,固定p H值4,通气量40 m L/min。电解40 min,50 mg/L的苯酚即可达到完全降解,电解2 h,COD的去除率可达91%,显示出良好的电化学催化活性,苯酚降解符合一级反应动力学。采用高温(600℃)煅烧重制电极,结果表明,新电极1 h对苯酚降解的去除率下降幅度不超过2%,显示出钛网良好的重复性能。研究了气体扩散阴极法对2,4-二氯苯酚的降解,并进行了脱卤和中间产物分析。实验结果表明,在电极间距3 cm,电流密度80 m A/cm2,电解质浓度0.2 mol/L,固定p H值4,通气量60 m L/min时,浓度50 mg/L的氯酚,电解1 h即可完全去除,电解2 h后COD去除率达到80%。根据脱氯结果显示,1 h后脱氯已经完成,阴极体系内氯离子浓度达到0.41 mmol/L。通过GC-MS对2,4-二氯酚降解进行中间产物检测,发现了2-氯酚、4-氯酚、苯酚、对二苯酚、苯醌、顺丁烯二酸等物质的生成。对气体扩散电极进行了表征分析,认为电极表面形貌及内部孔径分布不同,造成电极催化活性和选择性的差异,也是引起苯酚降解差异的主要原因,在炭黑/聚四氟乙烯(PTFE)为3、热压压力10 MPa下成型的电极表现出良好的性能。通过循环伏安曲线分析,推测苯酚主要在电极形成过氧化氢以及羟基自由基的间接氧化作用下被降解;2,4-二氯苯酚的去除先在电极还原脱氯的作用下,形成一氯酚和苯酚,继而通过间接氧化作用被降解。
[Abstract]:In recent years, environmental researchers have carried out extensive research in the field of electrochemical technology. At present, a new three-phase electrode-gas diffusion cathode. Catalytic removal of organic compounds and electrocatalytic reduction of halogenation by in-situ production of H _ 2O _ 2 and other strongly oxidized intermediates at the cathode have attracted much attention. A highly efficient gas diffusion electrode has been prepared in this paper. The electrode is composed of waterproof and permeable layer (gas phase layer, metal conducting network (solid phase layer), catalytic layer (liquid phase layer)), and directly uses air as oxygen source through degradation of phenol 2 + 4-dichlorophenol. The process system of gas diffusion cathodic catalytic treatment was established, and the effect of changing electrode operating conditions on the degradation of organic matter was studied. Combined with the method of characterization and electrochemical analysis, the gas diffusion cathode method for phenol 2 was analyzed. The degradation mechanism of 4-dichlorophenol. The effect of gas diffusion cathode on the degradation of phenol was investigated. The optimum conditions for phenol degradation by gas diffusion cathodic method were as follows: current density 80 Ma / cm 2, electrolyte concentration 0.2 mol / L, fixed pH 4. The phenol can be completely degraded by electrolysis for 40 min ~ 50 mg/L, and the removal rate of COD of electrolytic 2 h can reach 91%. The results showed that the electrochemical catalytic activity of the electrode was good and the degradation of phenol was in accordance with the first-order reaction kinetics. The electrode was prepared by calcination at high temperature (600 鈩，

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