Enhancement effects of [rad]O2− and [rad]OH radicals on NOX removal in the presence of SO2 by using an O3/H2O2 AOP system with inadequate O3 (O3/NO molar ratio = 0.5)

Abstract

The O3/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 O3 and H2O2 method with O3/NO molar ratio of 0.5. Besides, much O3 consumption, together with operating costs will be saved. The improved activity in O3/H2O2 is due to the increased generation amount of OH and O2−/HO2 radicals than the consumption amount of O3 when the molar ratio of O3/NO < 1, and the O2−/HO2 radical can selectively oxidize NO into HNO3 with a fast rate constant in a single step, while 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 O3/H2O2 method, resulting in the final 95% NOX removal with the O3/NO molar ratio of 0.5. Only NO3− ions can be detected as the liquid production through ion chromatography for the O3/H2O2 method. We expect that this study can shed some lights on the route design for simultaneous NOX and SO2 removal.