Visible-Light Photocatalytic Activity of Fe and/or Ni Doped Ilmenite Derived-Titanium Dioxide Nanoparticles.

Pure TiO₂ nanoparticles and ones doped with Fe and/or Ni were successfully prepared by a co-precipitation method from ilmenite. The samples were structurally characterized by XRD, XPS, FT-IR, UV-vis, SEM, EDX, AAS and BET measurement. The XRD results showed that all samples were anatase TiO₂, and no characteristic peaks of dopants were observed. The crystallite sizes of all doped TiO₂ nanoparticles were less than 20 nm and doping TiO₂ with metal ions can suppress the crystal growth of the particles. The XRD and XPS results indicated that TiO₂ was uniformly doped and its crystalline phase was not changed by doping. The specific surface area of Fe-Ni/TiO₂ is bigger than that of the un-doped TiO₂. The pore size and pore volume of Fe-Ni/TiO₂ is smaller than that of the un-doped. UV-vis spectra of the samples showed that the absorption edge red shifted with increasing doped metal content. The photocatalytic activity was evaluated in oxidative degradation of methylene blue (MB) with H₂O₂ under visible light irradiation. When doped with a single type of transition metal, the photocatalytic performance of Ni-doped samples was lower than that of Fe-doped ones. For the co-doped catalysts, the catalytic efficiency of 0.5%Fe₄%Ni/TiO₂ was the highest, reaching 93.34% after 250 min. Metal doping enhanced the photocatalytic decomposition of methylene blue compared with that of pure TiO₂ by up to 1.5 times. The synergistic effects of the two metal ions improved the photocatalytic performance. The particles exhibited pronounced activity in degradation of MB as well as efficient recyclability. The photocatalytic degradation mechanism of methylene blue was analyzed.