Enhancement effects of center dot O-2(-) and center dot OH radicals on NOX removal in the presence of SO2 by using an O-3/H2O2 AOP system with inadequate O-3 (O-3/NO molar ratio=0.5)

The O-3/H2O2 advanced oxidation process (AOP) was, for the first time, utilized for low-temperature NOx removal. The present method has a high NOx removal, which is 58% higher than the sum of that for single O-3 and H2O2 method with O-2/NO molar ratio of 0.5. Besides, much O-3 consumption, together with operating costs will be saved. The improved activity in O-3/H2O2 is due to the increased generation amount of center dot OH and center dot O-2(-)/HO2 center dot radicals than the consumption amount of O-3 when the molar ratio of O-3/NO < 1, and the center dot O-2(-)/HO2 center dot radical can selectively oxidize NO into HNO3 with a fast rate constant in a single step, while center dot OH can non-selectively oxidize NO and NO2 also at a fast rate constant. The SO2 in the flue gas even poses a positive effect on the NOx removal. Absorption by NaOH solution is generally followed by the O-3/H2O2 method, resulting in the final 95% NOx removal with the O-3/NO molar ratio of 0.5. Only NO3- ions can be detected as the liquid production through ion chromatography for the O-3/H2O2 method. We expect that this study can shed some lights on the route design for simultaneous NOx and SO2 removal.