Photocatalytic reduction of hexavalent chromium in aqueous solution over sulphate modified titania

Samples of different crystal forms and sizes of unmodified and sulphate modified TiO2 were prepared by varying pH, source and concentration of sulphate ion and by activating at different temperatures. Samples prepared at lower pH exhibit more surface area than that of higher pH. The percentage of photocatalytic reduction of Cr(VI) under solar radiation is higher at low pH and decreases with rise in pH of suspension. Presence of sacrificial electron donor such as EDTA enhances the photocatalytic reduction whereas presence of oxygen reduces it. Photocatalytic reduction of hexavalent chromium depends on surface area, the crystal form and particle size of TiO2. Samples containing mixtures of anatase and rutile phases exhibit highest activity for reduction of hexavalent chromium than that of single phases.