Rapid degradation of methylene blue using a dielectric barrier discharge plasma reactor with a water circulation system

Methylene blue (MB, C₁₆H₁₈ClN₃S) in water was efficiently degraded using a dielectric barrier discharge (DBD) plasma reactor. The air plasma generated by the flat-DBD system was introduced into the MB solution through a micro-bubbler. Despite the short lifetimes of the active species formed in plasma, they effectively decomposed contaminants upon contact with water. This study investigated the influence of various factors, including air flow rate, initial solution concentration, ozone production, and energy yield, on MB degradation. The results showed that the proposed plasma reactor could efficiently degrade MB. Furthermore, a mechanism to enhance the reaction rate was optimized using the flat-DBD plasma module and a 300-L circulating treatment system. With an initial MB concentration of 5 mg/L, one cycle from the 1000-L tank to the 300-L reactor took 50 min, achieving a 97.5 % degradation rate after 60 min. The energy yield for MB degradation was 22.5 g/kWh, and ozone production reached 3.9 g/h. A potential rapid degradation pathway for the MB solution is proposed in this study. This reactor design shows promising potential for applications related to the degradation of MB in dyeing wastewater and industrial processes.