Pd-MWCNTs-泡沫镍电极对2,4-二氯苯酚的电催化加氢脱氯研究

Electrocatalytic hydrodechlorination of 2,4-dichlorophenol by Pd-MWCNTs-foam nickel electrode

为发展废水中氯代酚的处理技术和保护水环境安全,采用"浸渍-干燥-电沉积"法制备钯-多壁碳纳米管-泡沫镍电极,研究电极对2,4-二氯苯酚(2,4-DCP)的去除能力和动力学特征,并探讨了2,4-DCP的脱氯机理.结果表明,在MWCNTs和Pd负载量分别为0.7 mg·cm^(-2)和0.01 mmol·cm^(-2)时制备的电极对2,4-DCP去除效果最好;掺入多壁碳纳米管(MWCNTs)可增大电极的表面积,提高Pd的分散性,增强电极的催化效率.当Na_(2)SO_(4)浓度为0.05 mol·L^(-1),工作电压为-1 V,反应液初始pH为7时,50 mg·L^(-1)的2,4-DCP降解90 min的去除率达到99.74%,降解过程符合一级反应动力学模型,速率常数为0.0667 min^(-1).采用高效液相色谱法监测2,4-DCP的降解产物,发现苯酚为2,4-DCP还原的最终产物,降解途径包括直接脱去2个氯原子转化为苯酚和分步脱去2个氯原子再转化为苯酚,但以直接脱去2个氯原子为主要途径.活性基淬灭实验证明,电极通过产生的吸附态氢原子(H_(ads))对2,4-DCP进行加氢脱氯.

In order to develop an electrochemical chlorophenol removal process in wastewater,a Pd-MWCNTs-nickel foam electrode was prepared by dipping,drying and electrodeposition.The electrocatalytic dechlorination capability and kinetics of 2,4-dichlorophenol(2,4-DCP)were studied,and the dechlorination mechanisms were discussed.The results showed that good removal performance could be obtained by the electrode prepared with the loading amounts of 0.7 mg·cm^(-2) MWCTs and 0.01 mmol·cm^(-2) Pd,respectively.MWCNTs could increase the surface area of the electrode and improve the dispersion of Pd,and thus enhance the catalytic performance of the electrode.Under the conditions of 0.05 mol·L^(-1) Na_(2)SO_(4) solution,-1 V applied voltage and reaction solution initial pH 7,the removal efficiencyreached 99.74% at 90 min for 50 mg·L^(-1)2,4-DCP.The degradation process could be described with the first-order reaction kinetic model,and the rate constant was 0.0667 min^(-1).The degradation products were monitored by high performance liquid chromatography,and phenol was found as the final reduction product.The degradation pathways included direct removal of two chlorine to phenol,and stepwise removal of two chlorine and then transformation into phenol,but the main approach was to remove two chlorine atoms directly.The active group quenching experiments proved that the hydrodechlorination reaction of 2,4-DCP was performed through the adsorbed hydrogen atoms(H_(ads))generated on the electrode.