Regeneration of Fe Modified Activated Carbon Treated by HNO3 for Flue Gas Desulfurization

The Fe/NAC for SO2 removal was prepared using incipient wetness impregnation. The fresh Fe/NAC exhibits good SO2 removal capacity and has a sulfur capacity of 231 mg/g, but in the SO2 removal process, the generated H2SO4 and Fe-2(SO4)(3) are deposited in a pore or on the surface of catalysts, causing the decrease of S-BET and V-micro, to 399 m(2)/g and 0.112 cm(3)/g. The thermal regenerative sample at different temperatures has different SO2 removal capacity, and the sample first regenerated at 900 degrees C under N-2 atmosphere achieves a sulfur capacity of 251 mg/g. Fe-2(SO4)(3) can be decomposed into Fe2O3 at 500 degrees C, but S-BET and V-micro recover to 733 m(2)/g and 0.243 cm(3)/g. Upon increase of regeneration temperatures from 700 to 900 degrees C, SO2 removal ability continues to increase, and Fe2O3 is reduced to Fe3O4 and Fe, but small Fe-2(SO4)(3) is still detected. S-BET and V-micro of Fe/NAC900-1 increase to 802 m(2)/g and 0.286 cm(3)/g. When the thermal-regeneration cycles at 900 degrees C increase from 1 run to 3 run, SO2 removal ability shows an obvious decrease. Fe2O3, Fe3O4, Fe, or Fe-2(SO4)(3) are detected, and the textures appears changes, but the residual Fe-2(SO4)(3) increases. However, the sample regenerated by the first water-washing has a sulfur capacity of 212 mg/g. When the regenerative cycles increase, sulfur capacity continues to decrease. Fe2O3, Fe3O4, Fe, or Fe-2(SO4)(3) are not obviously observed for the water-washing samples, but S-BET and V-micro increase to 899 m(2)/g and 0.316 cm(3)/g. After desulfurization, Fe-2(SO4)(3) is detected for fresh and regenerative samples, and the textures show an obvious decrease, resulting in catalyst deactivation. O-H and C-O are observed for all fresh and regenerative samples before and after desulfurization, and some new groups are observed for the regenerative samples, indicating that surface oxygen groups can be continually updated in the SO2 removal process because of the dissociative adsorption of oxygen.