Preparation of black sand-based magnetic photocatalysts for photocatalytic oxidation of aqueous phenol

A natural magnetic material, black sand, was used as cores to prepare a magnetic photocatalyst which, can be recovered using an external magnetic field. A surfactant-involved scheme was proposed to deposit a rough silica layer on the surface of black sand, which otherwise could not be coated with silica through a conventional scheme involving Stober process. Titanium dioxide (TiO2) was deposited on the surface of the silica-black sand (Si/BS) through an impregnation process and a direct deposition process. The catalytic property of the resultant photocatalyst (Ti/Si/BS) was evaluated using the oxidation of aqueous phenol and exhibited less reactivity than Degussa P25 TiO2. The phenol removal efficiency showed a pH dependence, which was ascribed to pH effect on (a) the formation of (OH)-O-center dot and (b) the electrostatic interaction between the photocatalyst and the substrate. The prepared photocatalyst is reusable despite slight deactivation caused by the mechanical loss of TiO2. (C) 2008 Elsevier B.V. All rights reserved.