Simultaneous removal of NO and SO from flue gas by combined heat and Fe activated aqueous persulfate solutions.

The use of advanced oxidation processes (AOPs) to integrate flue gas treatments for SO, NO and Hg 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 SO from flue gas utilizing AOP induced by the combined heat and Fe activation of aqueous persulfate, and elucidates the reaction pathways. The results indicated that both SO in the flue gas and Fe in solution improved NO removal, while the SO is almost completely removed. Increased temperature led to increase in NO removal in the absence and presence of both Fe and SO, and in the absence of either SO or Fe, but the enhanced NO removal due to the presence of SO 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 SO alone, and from 35.3% to 62.7% and 81.2%, respectively, in the presence of Fe alone. However, in the presence of both SO and Fe, 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 SO is equally effective by heat-only or heat-Fe activation as the temperature increases. The results should be useful for future developments of advanced oxidation processes for flue gas treatments.