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.

Enhanced degradation of tetracycline by gas-liquid discharge plasma coupled with g-C3N4/TiO2

“…Recently, research on water treatment by NTP has been explored. Magureanu et al [10] employed a pulsed dielectric barrier discharge (DBD) generated at the gas-liquid interface to degrade hexoketone theophylline pharmaceutical compounds, and a degradation g kWh −1 rate of 92.5% was achieved after 60 min of discharge with a corresponding energy yield of 16 . Hu et al [11] achieved almost complete degradation of the contaminant sulfamethoxazole by plasma jet treatment after 20 min.…”

“…When light radiation with an energy greater than the energy gap is irradiated onto the photocatalyst, the electrons in its valence band (VB) will be excited to leap to the conduction band (CB), resulting in surface redox [14,15]. In addition to the direct decomposition of antibiotic molecules [16], the process reacts with H 2 O and adsorbed oxygen to generate reactive radicals [17], thereby enhancing the degradation efficiency. TiO 2 is commonly used in energy-related and environmental applications due to its strong oxidation of organic compounds in wastewater, low toxicity and chemical stability [18,19].…”