Chemical Efficiency of H2O2 Production and Decomposition of Organic Compounds Under Action of DC Underwater Discharge in Gas Bubbles

A dc underwater discharge generated in gas bubbles (air, Ar, He, and N-2) in a NaH2PO4 center dot 2H(2)O solution is studied. It is shown that the maximal concentration of hydrogen peroxide produced in the discharge does not depend on gas composition. The energy efficiency of H2O2 production is, however, gas dependent, and the highest value of 2.95 g/kWh is obtained for air. The decomposition efficiency of the Direct Blue 106 dye, which is used as a model organic pollutant at an initial concentration of 20 mg/L, increases linearly with current in the investigated range (10-30 mA). A maximal dye decoloration of 65% is observed in a N-2 discharge after 20 min of treatment at a current of 30 mA. Different mechanisms of dye decoloration by plasma are proposed and discussed.