Discoloration and mineralization of non-biodegradable azo dye Orange II by copper-doped TiO2 nanocatalysts.

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.