Mechanistic research on NO removal by K2S2O8 with electrochemical catalysis

Nitrogen oxides have received extensive attention because they are key precursors of acid rain and photochemical reactions. The most widely used technologies for NO removal from flue gas involve reduction to N-2, which is difficult in multipollutant removal in integrated facilities. In this work, a novel method for NO oxidation by electrochemical catalysis in K2S2O8 was studied. The effects of K2S2O8 activation mode, electrode material and pH on the oxidation performance of electrochemically catalyzed K2S2O8 system were investigated. The results showed that the oxidative denitrification efficiency of electrochemical catalysis was higher than that of thermal, UV and transition metal activation of K2S2O8 and reached 89.3% with a Ti-based IrO2 electrode. Free radical quenching experiments demonstrated that 43.5% of the NO was oxidized by SO4 center dot-, HO center dot accounted for 30.2%, and another 15.6% was oxidized by 8% O-2 in the simulated flue gas and inactivated S2O82-. NO removal by the K2S2O8 electrochemical catalysis system was mainly derived from SO4 center dot- and HO center dot. The detection of free radicals by electron paramagnetic resonance (EPR) showed that the amount of HO center dot produced by electrochemical catalysis in K2S2O8 with a Ti-based IrO2 electrode was similar to that with a Ti-based RuO2 electrode but the amount of SO4 center dot- was much higher. In addition, the NO removal efficiency was maintained at more than 80% at various pH values, which meant that this novel method would present a wide range of pH adaptability in industrial applications.