Synchronous oxidation-removal of CO and NO using microwave-ultraviolet co-catalysis of H₂O/O₂ mixture

Exploiting innovative advanced oxidation technology to achieve oxidant-free self-purification of flue gas has always been a worthwhile topic. In this work, the synchronous oxidation-removal of CO and NO is fulfilled by the microwave-ultraviolet co-catalysis of H2O/O-2 mixture without external oxidant and catalyst, about 91 % of NO is converted into NO2-/NO3- and 98.12 % of CO is converted into CO2. To optimize this reaction system, the influences of MW power, catalytic temperature, UVEL lamp, contents of H2O, O-2 and SO2, concentrations of CO and NO as well as gas flow on the simultaneous removal efficiencies were investigated systematically, meanwhile, the synergistic interaction between MW and UVEL catalysis was unveiled, and the form and distribution of C- and N-containing substances were determined through ion chromatography (IC) and calculations. Via ESR tests, ozone measurements and radical quenching experiments, both center dot OH and center dot O-2(-) radicals and non-radical O-3 were identified as the prominent roles in the oxidative removal of NO and CO. Mechanism analyses further elucidated that the NO removal was dominated by the non-radical oxidation and the contribution order was O-3 (40.13 %) > center dot OH (38.76 %) > center dot O-2(-) (19.90 %), while the CO removal was mainly determined by the radical oxidation with a descending order of center dot OH (62.54 %) > center dot O-2(-) (24.69 %) > O-3 (6.41 %).