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

Abstract 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 oC) 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 oC, 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 oC. 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.