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 degrees C), the composite calcined at 300 degrees 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-SiO2Cs@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.