Theoretical and experimental studies of NO removal in alkaline H2O2 system

Abstract

NO in flue gas is one of the atmospheric pollutants, and it is necessary to study effective NO removal technology. It was identified that the alkaline H2O2 system achieved over 98 % NO removal efficiency with a gas–liquid contact time of 3 s in this paper. This paper investigates the mechanism of NO removal in alkaline H2O2 solution through both experimental and theoretical calculations. The results reveal the NO removal process can be divided into three phases by the NaOH/H2O2 molar ratio. (1) The ∙O2– dominated phase, where trace metal Fe catalyzes ∙O2– radical generation from H2O2 as Fe (OH)2+, reacting primarily with NO to form ONOO–. The energy barrier for this process is1.299 kcal/mol, with a reaction rate constant of 9.12 E + 11 s-1M−1. (2) The HO2– dominated phase, HO2– was generated through OH– and H2O2 neutralization, which converts NO to NO2 and regenerating OH–. The energy barrier for HO2– reacting with NO is 3.833 kcal/mol, and the reaction rate constant is 2.07E + 10 s-1M−1. (3) The O22– dominated phase, O22– was a further ionization of HO2– and converting NO to NO2– directly. The energy barrier for this process is 7.079 kcal/mol, and the reaction rate constant is 1.49 E + 08 s-1M−1.