Pd-Fe/石墨烯多功能催化阴极降解4-氯酚机制研究

制备出Pd-Fe/石墨烯多功能催化阴极,与Ti/Ir O2/Ru O2阳极、有机涤纶滤布构成隔膜电解体系,将阴极催化加氢脱氯作用和阴阳极氧化作用耦合起来对含4-氯酚的有机废水进行降解,采用TOC仪、紫外扫描、高效液相色谱、离子色谱分析方法研究其降解效果及反应历程.结果表明,在最佳反应条件下,Pd-Fe/石墨烯催化体系阴阳极室中4-氯酚转化率分别为98.1%和95.1%,优于Pd/石墨烯催化体系阴阳极室的93.3%和91.4%.Pd-Fe/石墨烯催化体系脱氯效果高于95%,表明双金属催化剂具有更强的析氢能力.在阴阳极的协同作用下,反应120 min时4-氯酚被完全转化.通过阴极加氢脱氯作用,4-氯酚被还原成苯酚.随后苯酚在阴阳极的共同氧化作用下,被氧化生成对二苯酚、苯醌等中间产物,继而被氧化为小分子有机酸,最后被矿化为CO2和H2O,据此提出了4-氯酚降解的可能历程.

Degradation Mechanism of 4-Chlorophenol on a Pd-Fe/graphene Multifunctional Catalytic Cathode

A Pd-Fe/graphene multifunctional catalytic cathode was prepared to build a diaphragm electrolysis system with a Ti/IrO₂/RuO₂ anode and an organicterylene filter cloth. The degradation of organic wastewater containing 4-chlorophenol by combination of cathodic hydrogenation dechlorination and oxidation of anode and cathode was investigated. The degradation process was monitored and characterized in aid of TOC analysis, UV-Vis spectra, high performance liquid chromatogram, and ion chromatogram. The results showed that the degradation efficiencies of 4-chlorophenol in the present system with Pd-Fe/graphene catalytic cathode were 98.1% (in cathodic chamber), 95.1% (in anodic chamber) under the optimal conditions, which were higher than those of the Pd/graphene catalytic cathode system (93.3% in cathodic chamber, 91.4% in anodic chamber). The chloride ion removal rate was more than 95% in the Pd-Fe/graphene catalytic cathode system, which suggested that the bimetallic catalyst had stronger hydrogenation capacity. 4-chlorophenol could be completely removed within 120 min under the synergetic effect of anodic-cathodic electrochemical degradation. In the cathodic chamber, 4-chlorophenol was initially reduced to form phenol under electrocatalytic hydrolysis. With further oxidation in both cathodic and anodic chambers, phenol was converted into hydroquinone and benzoquinone, then low molecular weight organic acids, and finally CO₂ and H₂O. Moreover, a reaction pathway involving all these intermediates was proposed.