UV/alcohol gas-phase oxidation combined with sulfite wet absorption for flue gas denitrification

Abstract

Developing novel advanced oxidation process (AOP) for flue gas denitrification is one of the hot topics in the field of air pollution control. Peroxides, persulfate and peroxymonosulfate are always used as the radical precursors, however it is seldom reported that alcohol species can be used in AOP process. This study first demonstrates that with the assistance of UV185 light, O2 and alcohol exhibit a great synergism in the NO removal. With the assistance of sulfite solution absorption, isopropanol (CH3CH(CH3)OH) and ethanol (CH3CH2OH) could remove 95.6% and 87.5% of NO, respectively, meanwhile the emitted NO2 concentration was controlled below 8 mg/m3. The apparent rate constant of NO removal by using UV185/CH3CH(CH3)OH-O2 and UV185/CH3CH2OH-O2 were calculated to be 0.07356 and 0.05712 s−1, respectively. But the presence of SO2 and CO2 were unfavorable for the NO removal. The formations of alcoxyl radicals, i.e. CH3CH2O• and CH3CH(CH3)O•, were verified by electron spin resonance tests (ESR). The overall reaction route was depicted via quantum chemistry calculation: alcoxyl radicals cooperate with NO* and O• to initiate two radical chain reaction cycles to realize the NO removal. The proposed new method can give new insights into the radical-induced removal of NO and guide the future design of AOP technology for flue gas denitrification.