Simultaneous photooxidation and photoreduction of phenol and Cr(VI) ions using titania modified with nanosilica

The photocatalytic process of phenol oxidation and Cr(VI) reduction in the presence of nano-silica modified titania was carried out. The activity of composites was tested using two different light sources. The photocatalysts with 10% of nanosilica showed the highest activity. The calcination temperature (200–800 °C) significantly determined the sensitivity of the obtained materials to the light source used. Photocatalysts alternately adsorbed and desorbed Cr(VI) ions from the reaction mixture during irradiation. In the one-component mixture, complete oxidation of phenol was observed using material calcined at 650 °C, after 3 h of UV-VIS irradiation. In the reaction mixture of Cr(VI) and phenol, the highest activity was demonstrated by photocatalyst calcined at 300 °C. The concentration of phenol decreased in proportion to the decrease of chromium ions. The obtained titania-silica composites showed oxidizing properties towards phenol and reductive properties toward Cr(VI) ions.