Development and photocatalytic activities of TiO2 doped with Ca-Ce-W in the degradation of acid red 1 under visible light irradiation

A stable visible light photocatalyst has successfully been developed by doping titanium dioxide (TiO2) with Ca, Ce, and W. Various combinations were developed and tested. The photocatalyst, when subjected to visible light photocatalytic degradation of C.I. Acid red 1 (AR1) showed an excellent performance in comparison with the most acclaimed commercial TiO2 photocatalyst, Degussa P25. The photocatalytic process with the best developed photocatalyst is "initial-concentration"-dependent, as high initial concentrations of AR1 dye precluded the photon energy from reaching the photocatalyst, and hence reduced its degradation rate. Initial pH of dye solution exerts its influence on the visible light photocatalytic degradation of the dye. High initial pH 10 was detrimental to the process, while the process was controlled by adsorption at lower pH 3. The developed photocatalysts were characterized by X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, X-ray diffraction, N-2 physisorption, surface scanning electron microscopy, and fourier transform infra-red spectroscopy. The results showed a red shift in the band gap of the tri-doped TiO2 from 3.2 to 2.94 eV indicating a shift in the onset optical wavelength from 387.19 to 421.43 nm.