Photocatalytic degradation of hexavalent chromium emerging contaminant via advanced titanium dioxide nanostructures

Photocatalysis is an attractive advanced treatment process that can be used for water purification from emerging contaminants, including hexavalent chromium (Cr(VI)) removal. Up to now, photocatalytic reduction of Cr(VI) has been investigated mostly using titania (TiO2) photocatalysts in acidic water solutions. In this work, copper (Cu) and cuprous oxide (Cu2O) nanoparticles (NPs) decorated TiO2-alginate beads were synthesized and studied in the photocatalytic reduction of Cr(VI) to Cr(III) under UV/Vis irradiation. The target was to overcome the drawback of pristine TiO2 which requires acidified solutions to achieve enhanced photocatalytic reduction of hexavalent chromium. Moreover, the spherical and uniform size of the photocatalytic beads ensures efficient mass transfer, addresses the problems of limited irradiation into slurries and facilitates separation of the catalyst after the photocatalytic treatment. The hexavalent chromium reduction efficiency of the Cu/Cu2O decorated TiO2/alginate beads was satisfactory at pH range 2-6 and practically did not depend on the treated solution acidity. Small quantities (10 g L−1) of the newly synthesized photocatalytic beads succeeded to remove all toxic loads from a 5 ppm Cr6+ solution in only 15 min under UV light irradiation. These low-cost developed and non-toxic photocatalysts seam greatly promising for Cr(VI) pollution cleanup.