NO removal from flue gas coupled with the FeⅡEDTA regeneration by UV irradiation

During wet complexation denitrification of flue gas, FeIIEDTA regeneration, also known as reducing FeIIIEDTA and FeIIEDTA-NO to FeIIEDTA is crucial. In this paper, ultraviolet light (UV) was used for the first time to reduce FeIIEDTA-NO. The experimental result demonstrated that FeIIEDTA-NO reduction rate increased with UV power increasing, elevated temperature, and initial FeIIEDTA-NO concentration decreasing. FeIIEDTA-NO reduction rate increased first and then decreased, as pH value increased (2.0-10.0). FeIIEDTA-NO reduction with UV irradiation presented a first order reaction with respect to FeIIEDTA-NO. Compared with other FeIIEDTA regeneration methods, FeIIEDTA regeneration with UV show more superiority through comprehensive consideration of regeneration rate and procedure. Subsequently, nitric oxide absorption experiment by FeIIEDTA solution with UV irradiation confirmed that UV can significantly promote the NO removal performance of FeIIEDTA. Appropriate oxygen concentration (3 vol%) and acidic environment (pH=4) was favorable for NO removal. With UV power increasing as well as temperature decreasing, NO removal efficiency rose. In addition, the mechanism research indicates that nitric oxide from flue gas is mostly converted to NO2–, NO3–, NH4+, N2 and N2O with FeIIEDTA absorption liquid with UV irradiation. UV strengthens NO removal in FeIIEDTA absorption liquid by forming a synergistic effect of oxidation-reduction-complexation. Finally, compared with nitric oxide removal methods with FeIIEDTA, FeIIEDTA combined UV system shows prominent technology advantage in terms of economy and secondary pollution.