Dechlorination and decomposition of trichloroacetic acid by glow discharge plasma in aqueous solution

Trichloroacetic acid (TCAA) is one of the most common, stable and carcinogenic byproducts in water and wastewater treatment. In this study, both dechlorination and decomposition of TCAA by glow discharge plasma (GDP) in a sodium sulfate solution were investigated. Intermediate products were identified and determined by ionic chromatography and GC-MS, respectively. It was shown that TCAA underwent successive dechlorination and decomposition under the action of GDP. Increasing pH and addition of organic additives to the solution were favorable for both the removal and the dechlorination. Major intermediate products were dichloroacetic acid, monochloroacetic acid, acetic acid and formic acid. Final products were inorganic carbon and chloride ion. Both radical and thermal reactions were involved in TCAA dechlorination and decomposition. Hydrogen atoms or hydrated electrons may be the most likely active species responsible for the decholorination, and hydroxyl radicals may be the most likely ones for the decomposition of the intermediate products. Reaction pathway was proposed based on the removal kinetics and the distribution of the intermediate products.