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 SO2 was achieved in a BiOI/Al2O3-padded trickling scrubber under visible light. The BiOI/Al2O3 composites, in which nanostructured BiOI was well dispersed on the surface of Al2O3, were successfully synthesized through solvothermal method. The prepared BiOI/Al2O3 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 SO2 was studied in a BiOI/Al2O3 trickling scrubber. It was found that the removal efficiency of NO and SO2 could reach 100% in photocatalytic BiOI/Al2O3-padded trickling scrubber, demonstrating that the present method performs well for simultaneous denitrification and desulfurization. The high removal efficiency for NO and SO2 was attributed to the enhanced gas absorption of BiOI/Al2O3 composites and the generation of reactive OH under visible-light irradiation in the system. The involvement of OH in oxidizing NO and SO2 was examined by determining the photocurrent of BiOI/Al2O3 and removal rates using different scavengers. Ion chromatography (IC) analysis identified that NO3− and SO42− were main products, and the mass balances analysis for N and S in scrubbing solution indicated that NO and SO2 were completely oxidized to be NO3− and SO42−. Most importantly, this BiOI/Al2O3 wet photocatalytic scrubber retained their simultaneous desulfurization and denitrification efficiencies for long-term repetitive batch runs, indicating the stable photocatalytic process.