Discoloration and Mineralization of Non-biodegradable Azo Dye Orange II by Copper-doped TiO₂ Nanocatalysts

Abstract

Copper-doped TiO₂ nanocatalysts were synthesized by photo-deposition and sol–gel methods. The nanocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and the BET method. The catalysts’ activities in the discoloration and mineralization of 0.2 mM Orange II were evaluated. The results indicated that the Cu-doped TiO₂ nanocatalysts with a low copper concentration prepared by the photo-deposition method showed enhanced photocatalytic activity; while catalysts synthesized by the sol–gel method did not. In particular, the TiO₂ nanocatalyst doped with 1% Cu showed the best performance. Complete color removal and 99% of total organic carbon (TOC) removal were achieved after 150-min of reaction. TiO₂ nanocatalysts doped with more than 1% Cu by the photo-deposition method showed decreased photocatalytic activities.

Keywords:

• Photocatalytic oxidation
• Azo dye
• Orange II
• Copper doping
• TiO₂

Acknowledgments

We are grateful to the Hong Kong Innovation and Technology Commission for the grant ITS 176/01C in support of this research. We thank Ms. Y. Zhang in MCPF at HKUST for her assistance in TEM experiment.