Simultaneous removal of NO and SO2 by Fe(II)/peracetic acid oxidation system: Operating conditions, removal efficiency and removal mechanism

Abstract

The request of synergistic control of PM2.5 and O3 pollution has made NO and SO2 emission control a hot topic again in the field of atmospheric environment. An advanced oxidation process (AOPs) for simultaneous removal of SO2 and NO from the flue gas of small and medium-sized boilers and kilns by Fe(II) activated peracetic acid (PAA) was investigated. The influences of operating parameters like reaction temperature, initial pH, concentrations of PAA and Fe(II) on SO2 and NO removal efficiency in Fe(II)/PAA system were studied. The NO removal efficiency was increased with higher PAA concentration and lower initial pH. Changes in reaction temperature and Fe(II) concentration had a dual effect on NO removal efficiency. The SO2 removal efficiency can be stably maintained above 99 % under all operating conditions, which is of great significance for practical engineering applications. Results indicated that the maximum removal efficiency of 92.3 % for NO and 99.5 % for SO2 were obtained under the optimal conditions of 100 mM PAA, 10 mM Fe(II), operating temperature 45 °C and initial solution pH 2.4. PAA was confirmed to play a major role in NO removal rather than coexistent H2O2. According to the electron paramagnetic resonance (EPR) technology, methyl phenyl sulfoxide (PMSO)-based probe experiments and radicals quenching experiments, reactive oxidizing species such as CH3C(O)O·, CH3C(O)OO·, ·OH and FeIVO2+ were generated in the Fe(II)/PAA system, where organic radicals (R-O•) were confirmed to be the major ones affecting NO oxidation. Ion chromatographic analysis revealed that SO42- and NO3- were the main products of SO2 and NO removal, and the mechanism of SO2 and NOx oxidation and removal by Fe(II)/PAA system was thus elucidated, which would promote the industrial application of this novel method.