Simultaneous absorption of SO and NO from flue gas using ultrasound/Fe/heat coactivated persulfate system.

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