Degradation of 2,4-dichlorophenol by cathodic microarc plasma electrolysis: characteristics and mechanisms

In this work, we used cathodic microarc plasma electrolysis (CMPE) to degrade 2,4-dichlorophenol (2,4-DCP) in simulated wastewater. By investigating and comparing the removal efficiencies and chemical oxygen demand (COD) during the degradation process, higher bath voltage and alkaline condition were considered as more suitable for the 2,4-DCP decomposition. Higher initial 2,4-DCP concentration was attributed to the increase in the utilisation of the energy input. The plasma characteristics during CMPE were studied by optical emission spectroscopy (OES). It was found that the 2,4-DCP directly participated in the plasma discharge process. Furthermore, by studying the evolution of intermediate products at different experimental parameters, it was found that the existence of Cl^- played an important role in the opening of benzene ring, which activated the ortho-substitutions of hydroxyl, meanwhile accelerated the p-substitutions. The instantaneous high temperature and high pressure and the Cl^- that were generated and driven by cathodic plasma made the decomposition of 2,4-DCP much quicker.