Methylene blue removal by submerged plasma irradiation system in the presence of persulfate.

The submerged plasma irradiation (SPI) system is utilized in applications and implications of many environmental fields as an advanced oxidation technology (AOT). However, ramifications of the SPI-based technologies for water treatment are constrained by the different inadequacies. To overcome this matter, in this study, the influence of added persulfate such as peroxydisulfate (PDS) or peroxymonosulfate (PMS) on the removal efficiency of methylene blue (MB) in the SPI system was investigated. The SPI-PMS system was the most effective for MB removal. Also, the pseudo first order rate constants of MB degradation increased with the increase of persulfate dose, applied voltage, and initial solution pH values. The radical species responsible for both the PDS and PMS-activated systems are likely to be peroxomonosulfate radicals (i.e., SO5 (·-)), sulfate radicals (SO4 (·-)), and hydroxyl radicals ((·)OH). Additionally, the persulfate-based SPI system is a novel AOT capable of producing SO4 (·-)or (·)OH and oxidizing water pollutants at near neutral pH.