Simultaneous removal of NO and SO2 from flue gas by combined heat and Fe2+ activated aqueous persulfate solutions

Abstract

The use of advanced oxidation processes (AOPs) to integrate flue gas treatments for SO2, NOx and Hg0 into a single process unit is rapidly gaining research attention. AOPs are processes that rely on the generation of mainly the hydroxyl radical. This work evaluates the effectiveness of the simultaneous removal of NO and SO2 from flue gas utilizing AOP induced by the combined heat and Fe2+ activation of aqueous persulfate, and elucidates the reaction pathways. The results indicated that both SO2 in the flue gas and Fe2+ in solution improved NO removal, while the SO2 is almost completely removed. Increased temperature led to increase in NO removal in the absence and presence of both Fe2+ and SO2, and in the absence of either SO2 or Fe2+, but the enhanced NO removal due to the presence of SO2 alone dominated at all temperatures. The removal of NO increased from 77.5% at 30 °C to 80.5% and 82.3% at 50 °C and 70 °C in the presence of SO2 alone, and from 35.3% to 62.7% and 81.2%, respectively, in the presence of Fe2+ alone. However, in the presence of both SO2 and Fe2+, NO conversion is 46.2% at 30 °C, increased only slightly to 48.2% at 50 °C; but sharply increased to 78.7% at 70 °C compared to 63.9% for persulfate-only activation. Results suggest NO removal in the presence of SO2 is equally effective by heat-only or heat-Fe2+ activation as the temperature increases. The results should be useful for future developments of advanced oxidation processes for flue gas treatments.