Influence of Cr3+ Concentration on SO2 Removal over TiO2 Based Multi-walled Carbon Nanotubes

In this study, titanium dioxide supported by multi-walled carbon nanotubes (MWCNTs/TiO2) and Cr-doped TiO2 supported by MWCNTs (MWCNTs/Cr-TiO2) were synthesized by the sol-gel method. The prepared samples were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, the Brunauer- Emmett-Teller analysis, and the Raman spectroscopy. The oxidation and efficiency for removal of SO, in a simulated flue gas were investigated experimentally in a fixed-bed reactor. The 15% MWCNTs/Cr-TiO2 sample displayed excellent adsorption properties, and a SO2 removal rate equating to 30.415 1 mg/g from the simulated flue gas containing 2 300 mu g/g of SO2, 8% of O-2, and 5% of H2O was achieved under optimal conditions covering a temperature of 333.15 K, and a space velocity of 1 275 h(-1). The adsorption process was enhanced because Cr doping modified the pore structure and inhibited the grain growth of TiO2. In addition, the Freundlich and Langmuir models revealed that SO2 was mainly adsorbed through chemical adsorption on the sample surfaces, and the thermodynamic model analysis indicated that the adsorption was a spontaneous, exothermic, and entropy-reducing process. The adsorption kinetics of SO2 can be described by the pseudosecond-order kinetic and the Bangham dynamics models. The possible reaction mechanism involved in desulfurization process was also proposed.