Degradation of methyl orange using dielectric barrier discharge water falling film reactor

The dielectric barrier discharge (DBD) technique based cylindrical water falling film reactor was used for degrading an azo dye methyl orange (MO). The primary conditions affecting the degradation of methyl orange were systematically investigated. After 30 min plasma treatment, the degradation rate of MO was as high as 93.7% with gas velocity of 300 mL/min and the input energy of 72.5W. The influences of initial pH and conductivity of MO solution were also explored. The results indicated that the optimum pH value was 3.02 and 99.1% removal of MO was achieved within 30 min. Three catalytic systems DBD/Fe2+, DBD/PS (persulfate) and DBD/Fe2+/PS were examined to improve the degradation rate and the chemical oxygen demand (COD) removal rate of MO. The highest degradation rate (100%) and COD removal rate (72.4%) happened in DBD/Fe2+/PS system. The degradation products were analyzed by LC-MS in DBD system and DBD/Fe2+/PS system respectively, and then the possible degradation pathways of MO were proposed.