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 TiO2 adsorbed gold nanoparticles and perylene (Au/Pe/TiO2) 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/TiO2 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/TiO2 (0.0545 min(-1)) was higher than that of TiO2 (0.0218 min(-1)), Pe/TiO2 (0.0303 min(-1)), or Au/TiO2 (0.0393 min(-1)). Gold nanoparticles and perylene synergistically accelerated the TiO2 photocatalytic reaction. This result is due to the Z-scheme electron transfer between Pe and TiO2 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/TiO2. In addition, successive reduction of the Cr(VI) was achieved by using a column packed with the Au/Pe/TiO2 powder immobilized by calcium alginate gel.