Photocatalytic reduction of hexavalent chromium in aqueous solution over titania pillared zirconium phosphate and titanium phosphate under solar radiation

The photo-reduction of hexavalent chromium was carried out varying different parameters such as pH, titania loading on zirconium phosphate (ZrP) and titanium phosphate (TiP), initial substrate concentration, irradiation time and catalyst dose. The reduction rate of chromium was favorable under acidic pH than in the alkaline pH. The dissolved oxygen imparts the minimum effect on the reduction of Cr(VI) as oxygen competes with the hexavalent chromium for the electron in the acidic solutions. Hexavalent chromium was completely reduced over titania pillared ZrP and TiP under solar radiation. This process of photo-reduction follows approximately pseudo first-order kinetics.

Graphical abstractThe photo-catalytic reduction of Cr(VI) under solar radiation depends on the surface area, basal spacing and crystallite size of the titania pillared zirconium phosphate (ZrP) and titanium phosphate (TiP). The 2 and 4 wt.% titania loaded ZrP and TiP show highest Cr(VI) photo-reduction under solar radiation compared to other pillared ZrP and TiP. Almost complete Cr(VI) photo-reduction takes place (20 mg/L) at pH 2.0 in 4 h with 0.6 g/L of the catalyst: Figure optionsDownload full-size imageDownload as PowerPoint slide