Non-thermal atmospheric pressure positive pulsating corona discharge in degradation of textile dye Reactive Blue 19 enhanced by Bi2O3 catalyst

Abstract Monoclinic Bi2O3 was applied for the first time, to the best of our knowledge, as a catalyst in a process of the dye degradation by the non-thermal atmospheric pressure positive pulsating corona discharge. The research focused on the interaction of the plasma-generated species and the catalyst, as well as its role in the degradation process. Plasma decomposition of the anthraquinone reactive dye Reactive Blue 19 (RB 19) was performed by the self- made reactor system. Bi2O3 was prepared by electrodeposition followed by thermal treatment, and characterized by XRD, SEM and EDX techniques. It was observed that the catalyst promoted decomposition of plasma-generated H2O2 into •OH radicals, the principle dye-degrading reagent, which further attacked the dye molecules. The catalyst improved the decolorization rate by 2.5 times, the energy yield by 93.4%, and the total organic carbon TOC removal by 7.1%, respectively. The excitation of the catalyst mostly occurred through the strikes of plasma-generated reactive ion and radical species from the air, accelerated by the electric field, as well as by the fast electrons with the energy of up to 15 eV, generated by the streamers reaching the liquid surface. Those strikes transferred the energy to the catalyst and created the electrons and holes which further reacted with H2O2 and water, producing the •OH radicals. This was indentified as the primary role of the catalyst in this process. Decolorization reactions followed the pseudo first order kinetics. Production of H2O2 and dye degradation rate increased with the increase of input voltage. The optimal catalyst dose was 500 mg dm-3. Decolorization rate was little lower in the river water compared to the one in deionized water due to the side reactions of •OH radicals with the organic matter and inorganic ions dissolved in the river water.