Absorption of NO and Simultaneous Absorption of SO2/NO Using a Vacuum Ultraviolet Light/Ultrasound/KHSO5 System

Absorption of NO from flue gas using vacuum ultraviolet (VUV)-light-activated KHSO5 solution in the presence of ultrasound (US) in a VUV US reactor was studied. The influencing factors, active species, products, and mechanism of NO removal were investigated. The results indicate that 185 nm is the most effective light wavelength for NO removal. US enhances NO removal as a result of the enhancement of mass transfer and chemical reaction (low frequency is more effective than high frequency). NO removal efficiency increases at a higher KHSO5 concentration, light intensity, or ultrasonic power density. Solution pH and temperature have an obvious double effect on NO removal. The key active species, such as ozone, hydroxyl radicals, and sulfate radicals, were successfully captured. The VUV/US/KHSO5 coupling system had the highest free radical yield and NO removal efficiency. NO removals by oxidations of free radicals and O./O-3 are the main removal routes. Simultaneous absorption of SO2/NO and potential applications of the removal process were also discussed initially.