PREPARATION, CHARACTERIZATION AND ORANGE II REMOVAL UNDER VISIBLE LIGHT RADIATION OF Cu-Ni/Ti02 PHOTOCATALYST

Photocatalytic degradation of a model azo dye, Orange II, was investigated over
bimetallic Cu-Ni/Ti02 photocatalysts. In the present study the introduction of Cu and
Ni onto Ti02 surface was with the intention to reduce the band gap of the
photocatalyst for enhanced visible light absorption via three methods: co precipitation
(CP), deposition-precipitation (DP) and wet impregnation (WI) methods with
different Cu:Ni mass composition (10:0, 9:1,7:3,5:5,3:7, I :9 and 0:10). The physical
and chemical properties of the modified Cu-Ni doped photocatalysts were
investigated using Thermogravimetric Analysis (TGA), Fourier-Transformed Infrared
Spectroscopy (FTIR), Point of Zero Charge (PZC) determination, powder X-ray
Diffraction (XRD), BET surface area analysis, Field-emission Scanning Electron
Microscopy-Energy Dispersive X-Ray Spectroscopy (FESEM-EDX), High
Resolution Transmission Electron Microscopy (HRTEM), Diffuse Reflectance UV�Vis Spectroscopy (DRUV-Vis) and Temperature-programmed Reduction (TPR). The
raw photocatalysts were activated by calcination at three different temperatures
(180°C, 200°C and 300°C) for I h duration. The PZC of Cu-Ni/Ti02 photocatalyst
shifts to a more basic value compared to the bare Ti02 (3.8). Photocatalyst particles
were spherical with slight agglomeration and high metal dispersion was achieved
confirmed by XRD and FESEM-EDX analyses. The presence of Cu-Ni mixed oxide
was detected by TPR analysis. The surface area of Cu-Ni/TiOz photocatalysts was
higher compared to that of bare TiOz. Incorporation of Cu, Ni, and Cu-Ni onto Ti02
resulted in the shift of absorption spectra into visible region with reduced bandgap
energy (2.74 eV) as confirmed by DRUV-Vis spectroscopy. The synthesized Cu�Ni/Ti02 photocatalysts were screened for Orange II decoloration efficiency against
different reaction parameters. The parameters studied were the effect of different
photocatalysts preparation methods, calcination temperature, Cu:Ni mass
composition, initial pH, metal loading, photocatalyst loading, initial dye concentration
and oxygen bubbling.