Degradation of 2,4-dichlorophenol in wastewater by low temperature plasma coupled with TiO2 photocatalysis

Abstract

Degradation of 2,4-dichlorophenol (2,4-DCP) in wastewater was conducted in a dielectric barrier discharge (DBD) reactor coupled with TiO₂ photocatalysis. The main advantage of the system is that ultraviolet (UV) light produced by the DBD and reactive species like ozone (O₃) can be used for the treatment of wastewater. In this study, the effect of discharge voltage, initial concentration and initial pH on the degradation of 2,4-DCP was studied. TiO₂ and I–TiO₂ were introduced to enhance the removal efficiency of 2,4-DCP. We also investigated the effect of adding tert-butanol to probe the role of hydroxyl radicals in the reaction. The results indicated that 2,4-DCP could be removed effectively and hydroxyl radicals played an important role during the degradation process by the low temperature plasma. The removal efficiency of 2,4-DCP with I–TiO₂ was better than with TiO₂. The degradation efficiency with 10% I–TiO₂ was 89.59% after 120 min when the discharge voltage was 75 V, pH 5.32 and 50 mg L⁻¹ was selected as the initial concentration. The removal efficiency of 2,4-DCP decreased with the increasing concentration of tert-butanol because alcohols are excellent radical scavengers that inhibit the generation of hydroxyl radicals during the DBD process. The degradation products of 2,4-DCP were characterized qualitatively and quantitatively using Mass spectrometry and UV-Vis spectroscopy. Besides, the degradation mechanism, the degradation pathway and the structures of intermediate products were also examined and discussed in detail.