Artificial Solar Light-Driven APTES/TiO(2) Photocatalysts for Methylene Blue Removal from Water

A visible-light photocatalytic performance of 3-aminopropyltriethoxysilane (APTES)-modified TiO(2) nanomaterials obtained by solvothermal modification under elevated pressure, followed by calcination in an argon atmosphere at 800–1000 °C, is presented for the first time. The presence of silicon and carbon in the APTES/TiO(2) photocatalysts contributed to the effective delay of the anatase-to-rutile phase transformation and the growth of the crystallites size of both polymorphous forms of TiO(2) during heating. Thus, the calcined APTES-modified TiO(2) exhibited higher pore volume and specific surface area compared with the reference materials. The change of TiO(2) surface charge from positive to negative after the heat treatment increased the adsorption of the methylene blue compound. Consequently, due to the blocking of active sites on the TiO(2) surface, the adsorption process negatively affected the photocatalytic properties. All calcined photocatalysts obtained after modification via APTES showed a higher dye decomposition degree than the reference samples. For all 3 modifier concentrations tested, the best photoactivity was noted for nanomaterials calcined at 900 °C due to a higher specific surface area than materials calcined at 1000 °C, and a larger number of active sites available on the TiO(2) surface compared with samples annealed at 800 °C. It was found that the optimum concentration for TiO(2) modification, at which the highest dye decomposition degree was noted, was 500 mM.