Oxidative removal of NO from flue gas using ultrasound, Mn2+/Fe2+ and heat coactivation of Oxone in an ultrasonic bubble reactor

A novel process about oxidative removal of NO from flue gas using ultrasound, Mn2+/Fe2+ and heat coactivation of Oxone in an ultrasonic bubble reactor was developed. The feasibility, main influencing factors, free radicals, products and mechanism of NO removal were studied. The results show that ultrasound enhances NO removal due to enhancement of mass transfer and chemical reactions (low-frequency ultrasound is more efficient than high-frequency). Removal of NO is enhanced at higher Mn2+/Fe2+ concentration, Oxone concentration, ultrasonic energy density, solution height, solution temperature or oxygen concentration, and is inhibited with the increase of NO concentration or flue gas flow rate. SO2 concentration and solution pH have a double effect on NO removal. Ultrasound, Mn2+/Fe2+ and heat coactivation system of Oxone has the highest free radical yield and NO removal efficiency. NO removal by oxidations of SO4−/OH radicals produced from ultrasound, Mn2+/Fe2+ and heat coactivation of Oxone is the main NO removal route. The effects of inorganic anions and particulate matters on NO removal, and simultaneous removal of SO2 and NO were also investigated.