Simultaneous detoxification of hexavalent chromium and acid orange 7 by a novel Au/TiO2 heterojunction composite nanotube arrays

Gold nanotubes consisting of compact and tiny Au particles were embedded in the pores of anodic TiO2 nanotube arrays by a simple pulse electrodeposition technique, constructing a novel metal-semiconductor heterojunction with a tube-in-tube structure. Under illumination, the electric potential difference generated on the interface of Au/TiO2 heterojunction facilitated the separation of the photogenerated hole-electron pairs, accelerating the transferring rate of the electrons and resulting in an enhanced photocatalytic activity. In comparison with the single system, simultaneously enhanced photocatalytic degradation rate of acid orange 7 (AO7) and reduction rate of Cr(VI) were observed due to the synergetic effect of Cr(VI)-AO7. Investigation results show that acidic solution is favorable for both the photocatalytic reduction of Cr(VI) and the degradation of AO7. The possible roles of the additives on the reactions are also discussed. (C) 2011 Elsevier B.V. All rights reserved.