A wet process for oxidation-absorption of nitric oxide by persulfate/calcium peroxide

This study develops and evaluates a novel wet method for NO removal using a Na2S2O8/CaO2 solution. The effects of these two components both and alone in solution, Na2S2O8 concentration, CaO2 concentration, initial pH, reaction temperature, and the concentrations of NO and O2 on NO removal efficiency were evaluated using a bubbling reactor. The combination of Na2S2O8 and CaO2 had a synergistic effect on NO removal efficiency. NO removal was effected by CaO2 concentration, reaction temperature and the initial solution pH, while Na2S2O8 concentration and O2 concentration had little effect. The NO removal efficiency decreased linearly from 94.5 % to 75.1 % when the NO concentration increased from 139 to 559 ppm. The products were characterized using XRD, XPS and IC, and CaSO4·2H2O, NO3− and SO42− were found to be the main products. The EPR analysis showed that free radicals of O2−, SO4− and OH were the key species involved in the NO removal process. Finally, the corresponding reaction mechanisms were proposed.