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

It was found that, among these chitosan@TiO 2 (Cs@TiO 2 ) composites calcined at different temperatures (200, 300, 400, 500 and 600 °C), the composite calcined at 300 °C (Cs@TiO 2 -300) showed the best adsorption and photocatalytic activity . To eliminate the limitation of recycling catalyst nanoparticles , the PDMS-SiO 2 -Cs@TiO 2 composites with hydrophobic surfaces were prepared for dye degradation by embedding Cs@TiO 2 -300 nanoparticles into a PDMS-SiO 2 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-SiO 2 -Cs@TiO 2 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-SiO 2 -Cs@TiO 2 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@TiO 2 -300 composites and PDMS-SiO 2 -Cs@TiO 2 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-SiO 2 -Cs@TiO 2 composites.