Simultaneous photocatalytic elimination of gaseous NO and SO2 in a BiOI/Al2O3-padded trickling scrubber under visible light

Abstract The simultaneous photocatalytic elimination of NO and SO 2 was achieved in a BiOI/Al 2 O 3 -padded trickling scrubber under visible light. The BiOI/Al 2 O 3 composites, in which nanostructured BiOI was well dispersed on the surface of Al 2 O 3 , were successfully synthesized through solvothermal method. The prepared BiOI/Al 2 O 3 was characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (DRS). The elimination of NO and SO 2 was studied in a BiOI/Al 2 O 3 trickling scrubber. It was found that the removal efficiency of NO and SO 2 could reach 100% in photocatalytic BiOI/Al 2 O 3 -padded trickling scrubber, demonstrating that the present method performs well for simultaneous denitrification and desulfurization. The high removal efficiency for NO and SO 2 was attributed to the enhanced gas absorption of BiOI/Al 2 O 3 composites and the generation of reactive OH under visible-light irradiation in the system. The involvement of OH in oxidizing NO and SO 2 was examined by determining the photocurrent of BiOI/Al 2 O 3 and removal rates using different scavengers. Ion chromatography (IC) analysis identified that NO 3 − and SO 4 2− were main products, and the mass balances analysis for N and S in scrubbing solution indicated that NO and SO 2 were completely oxidized to be NO 3 − and SO 4 2− . Most importantly, this BiOI/Al 2 O 3 wet photocatalytic scrubber retained their simultaneous desulfurization and denitrification efficiencies for long-term repetitive batch runs, indicating the stable photocatalytic process.