Selective reactive oxygen and nitrogen species production in plasma-activated water via dielectric barrier discharge reactor: An innovative method for tuning and its impact on dye degradation
Saeed Kooshki, Pankaj Pareek, Mário Janda, Zdenko Machala
Abstract
Water treated by non-thermal gas plasma shows a great potential across various applications, e.g. in wastewater cleaning, agriculture, and bio-medicine. Maximizing the plasma water treatment efficacy requires precise control over reactive oxygen/nitrogen species (RONS) concentrations. This study emphasizes the importance of tuning the plasma system for selective production of RONS in water, for both higher operational efficacy and better economic efficiency in dye wastewater treatment. We propose an innovative approach for tuning RONS. In particular, ceramic electrode (Ce) and higher reactor temperatures result in a higher hydrogen peroxide (H2O2) production in PAW, up to 16 mg.l−1 within 30 min, and minimal nitrite production. Conversely, copper electrode with water-cooling system (Cuw) result in higher nitrite concentrations, up to 80 mg.l−1 within the same treatment time, but negligible H2O2 production. Selective RONS production significantly affects methylene blue dye degradation. Ce setup yields an efficient dye degradation (1.04 g.kWh−1), while Cuw setup proves inefficient and synthesizes additional by-products in water by nitration mechanism. Finally, a total cost estimation analysis showed that potentially scaled-up plasma technology operates at low energy costs if compared with advanced oxidation processes. Selective RONS production for the dye degradation can lead to almost 30 % reduction in the total costs.