Simultaneous removal of SO2, NO and mercury using TiO2-aluminum silicate fiber by photocatalysis

A novel TiO2-aluminum silicate fiber (TAS) nanocomposite, synthesized by a sol-gel method, is proposed to use as a photocatalyst for the removal of multiple pollutants. The photocatalyst has been characterized by XRD, SEM, EDX, UV-Vis spectra and BET. The TAS calcined at 500 degrees C exhibited the biggest BET surface area and highest photocatalytic activity and was used as the photocatalyst for subsequent experiments. The oxidation and removal efficiencies of SO2, NO and elemental mercury (Hg-0) in simulated coal combustion flue gas by the TAS catalyst were tested under UV irradiation. Experiments were conducted in a fixed-bed reactor at temperatures ranging from 30 to 120 degrees C. In simulated flue gas (4% O-2, 12% CO2, 2% H2O, 400 ppm SO2, 50 ppm NO), the removal efficiencies for SO2, NO and Hg-0 at 120 degrees C and with UV intensity of 3 mW cm(-2) can reach 33%, 31% and 80%, respectively. NO inhibited SO2 oxidation due to its competition for active adsorption sites. SO2 also had a prohibitive effect on NO removal. In contrast, SO2 was found to have a promotional effect on Hg-0 oxidation due to the formation of HgSO4. NO inhibited the photocatalytic removal of mercury. During the simultaneous removal of SO2, NO and Hg-0 on TAS, the photocatalytic oxidation efficiency decreased from 30 to 120 degrees C. O-2 exhibited a promotional effect on the photocatalytic oxidation due to the formation of lattice oxygen. However, the addition of water vapor to the simulated flue gas inhibited the oxidation of SO2, NO and Hg-0. The UV intensity was the most important factor in the photocatalytic oxidation. Our discussion on the possible reaction mechanism provides some useful information for developing effective photocatalysts to oxidize SO2, NO and Hg-0 in simulated coal combustion flue gas. (C) 2012 Elsevier B.V. All rights reserved.