Photoreduction of Cr(VI) by TiO2 adsorbed gold nanoparticles and perylene as a novel organic–inorganic hybrid photocatalyst

The photoreduction of hexavalent chromium (Cr(VI)) using TiO 2 adsorbed gold nanoparticles and perylene (Au/Pe/TiO 2 ) as a novel organic–inorganic hybrid photocatalyst has been studied. The irradiation by a Xe lamp of a Cr (VI) aqueous solution (0.1 mM) with the Au/Pe/TiO 2 powder resulted in the reduction of the Cr(VI). The rate of Cr(VI) reduction reached 98.3% by the irradiation for 60 min. The reaction rate constant using Au/Pe/TiO 2 (0.0545 min −1 ) was higher than that of TiO 2 (0.0218 min −1 ), Pe/TiO 2 (0.0303 min −1 ), or Au/TiO 2 (0.0393 min −1 ). Gold nanoparticles and perylene synergistically accelerated the TiO 2 photocatalytic reaction. This result is due to the Z-scheme electron transfer between Pe and TiO 2 and the suppression of charge recombination by the gold nanoparticles. The irradiation of sunlight also led to the photocatalytic reduction of the Cr(VI) by Au/Pe/TiO 2 . In addition, successive reduction of the Cr(VI) was achieved by using a column packed with the Au/Pe/TiO 2 powder immobilized by calcium alginate gel.