Influence of cathode on the electro-generation of peroxydisulfuric acid oxidant and its application for effective removal of SO2 by room temperature electro-scrubbing process

Peroxydisulfuric acid oxidant (H2S2O8) was electro-generated using boron doped diamond (BDD) anode in an undivided electrolytic cell under the optimized conditions and used for the oxidative removal of gaseous SO2. The influence of the nature of cathode material on the formation yield of H2S2O8 was investigated with Ti, Pt, Zr and DSA electrodes in a flow type electrolytic cell under batch recirculation mode. Among the various cathodes employed Ti exhibited a good performance and the formation yield was nearly doubled (0.19 M) compared to the reported value of 0.07 M. The optimization of electrode area ratio between the anode and cathode brought out the fact that for nearly 8 times smaller Ti cathode (8.75:1) the achieved yield was ∼65% higher than the 1:1 ratio of anode and cathode. The highest concentration of 6.8% (0.48 M) H2S2O8 was seen for 35 cm2 BDD anode with 4 cm2 Ti at 20 °C with the measured redox potential value of +1200 mV. The oxidative removal of SO2 in an electro-scrubbing column attached to the online production of peroxydisulfuric acid under the optimized conditions of cell parameters shows that SO2 removal efficiency was nearly 100% for 25 and 50 ppm inlet concentrations and 96% for 100 ppm at the room temperature of 25 °C.