A facile synthesis of supported amorphous iron oxide with high performance for Cr(VI) removal from aqueous solution under visible light irradiation

A series of supported iron oxide nanoparticles were prepared by impregnation with Fe(NO₃)₃ supported on TiO_2, followed by low-temperature calcination. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra and BET have been used to characterize the samples. These iron oxide-impregnated TiO₂ were examined for photocatalytic reduction of Cr(VI). The experiments demonstrated that Cr(VI) in aqueous solution was more efficiently reduced using Fe₂O₃/TiO₂ heterogeneous photocatalysts than either pure Fe₂O₃ or TiO₂ under visible light irradiation. All TiO₂ supported samples were somewhat active for visible light photoreduction. With an optimal mole ratio of 0.05-Fe/Ti, the highest rate of Cr(VI) reduction was achieved under the experimental conditions. We also compared the photoreactivity of TiO₂ supported iron oxide samples with that supported on Al₂O₃ and ZrO₂. It can be noted that iron oxide nanoparticles deposited on high surface area supports to increase the solid-liquid contact area renders it considerably more active. Noticeably, iron oxide cluster size and dispersion are important parameters in synthesizing active, supported Iron oxide nanoparticles. In addition, the interaction between iron oxide and TiO₂ was proposed as the source of photoactivity for Cr(VI) reduction.