Adsorption characteristics and separation of Cr(III) and Cr(VI) on hydrous titanium(IV) oxide

A hydrous titanium(IV) oxide was prepared to study the adsorption characteristics and the separation of chromium species. Batch sorption studies have been carried out to determine the effect of pH on the sorption of Cr(III) and Cr(VI) on hydrous TiO 2. An excellent separation efficiency of Cr(III) and Cr(VI) was obtained at pH 2. The adsorption percentage of Cr(VI) was above 99%, whereas that of the Cr(III) was less than 1% at this pH. The adsorption isotherm of Cr(VI) on hydrous TiO 2 at pH 2 was in good agreement with the Langmuir isotherm. The maximum adsorption capacity of Cr(VI) on TiO 2 was 5 mg g −1. The rate of adsorption of Cr(VI) by hydrous TiO 2 with average particle diameter 250 and 500 μm has been studied under particle diffusion controlled conditions. The diffusion coefficients of Cr(VI) for both hydrous TiO 2 having average particle diameter of 250 and 500 μm was calculated at pH 2 as 3.84 × 10 −10 m 2 s −1 and 8.86 × 10 −10 m 2 s −1, respectively.