Simultaneous absorption of SO2 and NO from flue gas using ultrasound/Fe2+/heat coactivated persulfate system

A novel process on simultaneous absorption of SO2 and NO from flue gas using ultrasound (US)/Fe2+/heat coactivated persulfate system was proposed. The influencing factors, active species, products and mechanism of SO2 and NO removal were investigated. The results indicate that US enhances NO removal due to enhancement of mass transfer and chemical reaction. US of 28 kHz is more effective than that of 40 kHz. NO removal efficiency increases with increasing persulfate concentration, ultrasonic power density and Fe2+ concentration (at high persulfate concentration). Solution pH, solution temperature and Fe2+ concentration (at low persulfate concentration) have double effect on NO removal. SO2 is completely removed in most of tested removal systems, except for using water absorption. US, Fe2+ and heat have a synergistic effect for activating persulfate to produce free radicals, and US/Fe2+/heat coactivated persulfate system achieves the highest NO removal efficiency. ·OH and SO4−· play a leading role for NO oxidation, and persulfate only plays a complementary role for NO oxidation.