Decomposition of Organic Compounds by Microwave-induced Plasma in Liquid Phase

Abstract

Ability of several ceramic triggers to generate plasma has been investigated upon irradiation of 2.45 GHz microwave in pure water and in an aqueous solution of dichloroacetic acid or β-naphthol. After the liquids started boiling due to absorption of microwave power by water molecules, plasma was generated in the restricted vapor phase between the solid triggers and the surrounding liquid. When SiC and carbon block were used as a trigger, O and OH radicals were observed in the generated plasmas, but H radicals were formed preferentially when the trigger was La_0.8Sr_0.2CoO₃ or La_0.6Sr_0.4MnO₃. Dichloroacetic acid or β-naphthol could be decomposed by the plasma treatment, though volatile partial decomposition products were also formed. Decomposition of β-naphthol was more effective than that of dichloroacetic acid, especially when SiC was employed as a trigger. Thus, the present study confirmed the potential use of microwave-induced plasma for treating waste water.