Synergistic Effects of a Combination of Vacuum Ultraviolet–Induced Oxidation and Wet Absorption Process on Removal of Nitric Oxide at Room Temperature

Abstract

Removal of low concentration NO in enclosed space by a new combined process incorporating vacuum ultraviolet (VUV)-induced oxidation and wet absorption process at room temperature was studied. Effects of NO initial concentration, gas flow rate, and humidity on NO conversion in the VUV irradiation process were first investigated. Subsequently, the absorption aqueous solutions were optimized, and the Na2S2O3 inhibitor was used in the wet absorption process in order to absorb the generated NO2. The results demonstrated that NO conversion was increased with the decreasing initial concentration and gas flow rate, and moreover, humidity had a promoting effect on NO oxidation because of the generation of hydroxyl radicals (·OH) under VUV irradiation. Na2SO3 solution was favorable for the absorption of NO2, and the NOx conversion can reach 85% at the initial stage, while it was decreased to 25% after 20 min absorption for the rapid free radical chain reaction nature between Na2SO3 and NOx. In addition, the Na2S2O3 inhibitor was chosen to suspend the presented rapid reaction, the removal efficiency of NOx was increased with the augment of the Na2S2O3 concentration, and it can be stabilized at 85% even after 4 h reaction with the Na2S2O3 concentration of 1.5%.