Immobilized and photocatalytic performances of PDMS-SiO2-chitosan@TiO2 composites on pumice under simulated sunlight irradiation

It was found that, among these chitosan@TiO₂ (Cs@TiO₂) composites calcined at different temperatures (200, 300, 400, 500 and 600 °C), the composite calcined at 300 °C (Cs@TiO₂-300) showed the best adsorption and photocatalytic activity. To eliminate the limitation of recycling catalyst nanoparticles, the PDMS-SiO₂-Cs@TiO₂ composites with hydrophobic surfaces were prepared for dye degradation by embedding Cs@TiO₂-300 nanoparticles into a PDMS-SiO₂ sol-gel system. More concretely, with pumice stone as the support of composites, the experiment was carried out in a reaction bed. When pumice stones were used as supports for PDMS-SiO₂-Cs@TiO₂ composites, compared with its initial concentration, the concentration of dye solution decreased by 36% after 30 h of simulated sunlight irradiation. Additionally, the degradation efficiency of dyes hardly decreased after five cycles. The optical property and surface structure of PDMS-SiO₂-Cs@TiO₂ were characterized by UV–Vis DRS and XPS, respectively. It is noteworthy that the UV–Vis DRS results indicated that the light absorption range of both Cs@TiO₂-300 composites and PDMS-SiO₂-Cs@TiO₂ composites had been broadened to the visible light region. Moreover, the XPS results indicated the existence of nitrogen (N) doped titanium on the surface of PDMS-SiO₂-Cs@TiO₂ composites.