Reusable titania-SBA-15 photocatalyst synthesized by different silica/titania ratios for enhancing methylene blue photodegradation

Abstract

In this study, a series of TiO2/SBA-15 photocatalysts were synthesized with different Si/Ti ratios by a one-step hydrothermal method with TiO2 nano-powder as a titanium source. These materials were characterized by XRD, SEM-EDX, N2 adsorption-desorption isotherms-desorption isotherms, XRF, and UV-DRS analysis. During the synthesis of TiO2/SBA-15s, the SBA-15 pore structure and channels did not deteriorate, and the Si/Ti molar ratios are close to the expected nominal ratios. SBA-15 and TiO2/SBA-15s exhibited a uniform- narrow pore size distribution, but TiO2/SBA-15s pore size shifted to a smaller range, and the BET area values of TiO2/SBA-15s materials are in the range of the 621–583 m2/g. TiO2 nanocrystals into the SBA-15 mesopores walls wall up to the ratio of Si/Ti = 16. With high TiO2 loading of that value, clogging occurs in the SBA-15 pores. The optical band gap energies were significantly blue-shifted which is the quantization effects improving the photocatalytic activities Photocatalytic activities of TiO2/SBA-15s were evaluated by degradation of methylene blue under UV-light irradiation at constant TiO2 content. The highest efficiency was obtained in the TiO2/SBA-15 (16) photocatalyst at 79.6%, and all efficiencies in synthesized photocatalyst are higher than bulk TiO2 photocatalyst activity (27.52%) due to the poor dispersion of active phases. Reused photocatalyst has no activity losses for five runs and may be used for long periods without loss of activity. For the stability of the photocatalyst, a combination of XRD, SEM, and N2 adsorption-desorption isotherms was employed after the fifth run. These results demonstrate that the photocatalyst activity and stability are good, and photocatalytic activity was sustainable after reuse for several cycles.