Nitrogen Oxide Removal from Simulated Flue Gas by UV-Irradiated Sodium Chlorite Solution in a Bench-Scale Scrubbing Reactor

Abstract

Ultraviolet irradiated sodium chlorite (UV/NaClO2) solution was introduced to remove nitrogen oxide (NOx) from simulated flue gas in a bench-scale scrubbing reactor. Effects of UV irradiation time, NaClO2 concentration, NO inlet concentration, pH value, and O2 concentration were investigated separately. Results showed that NaClO2 solution with UV pretreatment achieved a remarkable promotion in NOx removal efficiency. The ClO2 produced from photodecomposition of NaClO2 in aqueous solution substantially improved the NO absorption process. The NOx removal efficiency by UV/NaClO2 solution increased from 28 to 77% as the UV irradiation time increased from 0 to 600 s. When the NaClO2 concentration increased, the NOx removal efficiency by UV/NaClO2 solution increased, whereas the enhancement factor decreased. The NO absorption rate by UV/NaClO2 solution increased with NO inlet concentration. The NOx removal efficiency by UV/NaClO2 solution was higher than that by NaClO2 solution without UV pretreatment at a pH range of 3–12. The reaction mechanisms of the NO removal process were suggested to be different in acid and alkaline media. The UV/NaClO2 process was demonstrated to significantly improve NOx removal efficiency, which might be developed to be a potentially cost-effective method for removing NOx from flue gas.