关键词: 氯酚, 电化学, 催化还原, 反应动力学, 速率常数

Abstract:

Chlorophenols are persistent organic pollutants with high toxicity. Dichlorophenols (DCPs) include six isomers due to different substituted position of chlorine atoms. Self-made Pd/polypyrrole(sodium dodecylbenzene sulfonate)/Ti electrode (Pd/PPy(SDBS)/Ti electrode) was employed to dechlorinate six DCP isomers. The effects of electrolysis current, initial pH and the initial concentration of target pollutant on the dechlorination process of 2,5-DCP were investigated. Under the selected conditions, i.e., applied current of 5 mA, initial pH of 2.5 and temperature of 25℃, dechlorination experiments of 2,3-DCP, 2,5-DCP, 2,4-DCP, 2,6-DCP, 3,4-DCP and 3,5-DCP with the same DCP concentration of 100 mg·L^-1 were conducted, respectively. Phenol was the main product and a small amount of monochlorophenol could be detected during the dechlorination of six DCPs. The reaction rate constants of six DCPs were 4.735×10^-2 min^-1, 4.609×10^-2 min^-1, 4.845×10^-2 min^-1, 4.317×10^-2 min^-1, 3.973×10^-2 min^-1 and 3.770×10^-2 min^-1, respectively. It showed that the degradation rates of DCPs were affected by pK_a, protonation and pH. The degradation difficulty of six DCPs was 2,4-DCP<2,3-DCP<2,5-DCP<2,6-DCP< 3,4-DCP<3,5-DCP.

Key words: chlorophenols, electrochemistry, catalytic reduction, reaction kinetics, rate constant