Photoreduction of toxic chromium using TiO2-immobilized under natural sunlight: effects of some hole scavengers and process parameters

This work focuses on the photocatalytic reduction of Cr(VI)-Cr(III) using TiO2-immobilized onto glass slides under natural sunlight. The commercial TiO2 Degussa P25 was used as a photocatalyst in this work. The effects of some additives as hole scavengers for Cr(VI) reduction are studied. The results show that their presence enhances the reduction rate in the order: tartaric acid > oxalic acid > EDTA > ethanol > methanol > no-additive. The optimization of tartaric acid concentration is determined. The effect of process parameters such as Cr(VI) concentration, pH, and the presence of interfering substances such as inorganic anions ( [GRAPHICS] , [GRAPHICS] , [GRAPHICS] , [GRAPHICS] and [GRAPHICS] ) and metallic cations ( [GRAPHICS] , [GRAPHICS] , [GRAPHICS] , and [GRAPHICS] ) is investigated. The results show that the removal rate is maximum at pH 1.5. On the other hand, the coexistence of interfering ions with Cr(VI) decreases the reduction rate except for the [GRAPHICS] . Finally, the results show that the TiO2-immobilized can be reused several times.