Simultaneous absorption-oxidation of nitric oxide and sulfur dioxide using ammonium persulfate synergistically activated by UV-light and heat

Simultaneous absorption-oxidation process of nitric oxide (NO) and sulfur dioxide (SO2) from flue gas using aqueous ammonium persulfate synergistically activated by UV-light and heat in a novel UV-impinging stream reactor was developed. The main influencing factors, products and active species of NO and SO2 simultaneous removal were studied. The mass transfer and kinetics of NO absorption-oxidation were also investigated. The present studies show that SO2 is very easy to remove because of its very high solubility in water (SO2 removal efficiencies reach 100% under most of experimental conditions). Increasing S2O82− concentration, UV radiation power, activation temperature or liquid-gas ratio promotes absorption-oxidation of NO. Increasing solution pH, concentrations of NO and SO2 or flue gas flow inhibits absorption-oxidation of NO. The contents of O2 and CO2 have no significant effect on removal of NO. The highest simultaneous removal efficiency for NO and SO2 is 96.1% and 100%, respectively. OH and SO4− are the key oxidizers for NO removal. Absorption-oxidation process of NO meets a fast pseudo-first order reaction for NO, and can be enhanced by increasing the gas-side mass transfer coefficient and interfacial area.