Dechlorination and Decomposition of Dichloroacetic Acid by Glow Discharge Plasma in Aqueous Solution

Dichloroacetic acid (DCAA) is one of the most common, stable and carcinogenic byproducts in water and wastewater treatment. In this study, dechlorination and decomposition of DCAA by glow discharge plasma (GDP) in a sodium sulfate solution were investigated. Intermediate products were identified and determined by ionic chromatography. Different experimental conditions are discussed for the influence of the removal efficiency of DCAA, such as different pH, hydroxyl radical scavenger. Increasing pH was favorable for both removal and dechlorination of DCAA. Addition of organic addictives to the solution decreased both the removal and dechlorination of DCAA. Monochloroacetic, acetic acid, formic acid and oxalic acid were the major products. Final products were inorganic carbon and chloride ion. The possible dechlorination mechanism is proposed based on the distribution of intermediate products. Both radical and thermal reactions were involved in the dechlorination and decomposition of DCAA. Hydroxyl radicals may be the most likely active species responsible for the dechlorination and decomposition.