Photocatalytic removal of SO2 over Mn doped titanium dioxide supported by multi-walled carbon nanotubes

In this paper, titanium dioxide supported by multi-walled carbon nanotubes (MWCNTs/TiO2), and Mn doped TiO2 supported by MWCNTs (MWCNTs/Mn-TiO2) were synthesized in a sol–gel method. Characterizations of these two prepared photocatalysts were analyzed by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance spectra (DRS). The results show that MWCNTs and Mn dopants inhibits the grain growth of TiO2. The excellent optical properties in UV and visible region were both observed on 0.5% MWCNTs/Mn-TiO2. The photocatalytic oxidation and removal efficiency of SO2 from simulated flue gas were investigated experimentally in a fix-bed reactor. Removal efficiency of SO2 can reach 69% while using 0.5% MWCNTs/Mn-TiO2 as photocatalysts at the optimal conditions (155 mg/m3 SO2, 8% O2, 5% H2O). The desulfurization efficiency was lower in the presence of NO due to the competition for adsorption sites between SO2 and NO. O2 and H2O played important roles in the photocatalytic oxidation of SO2. In addition, the possible reaction mechanism involved was also proposed here.