The removal mechanism of Cr(VI) by calcium titanate: Insight into the role of surface reduced Cr(III) in removal process

Pollution of the environment with hexavalent chromium (Cr(VI)) has attracted a lot of concern recently as the high toxicity and mobility of Cr(VI). Hence, the removal of Cr(VI) from aquatic systems has become an urgent issue. In this study, we synthesized an efficient photocatalyst of cubic CaTiO3 particles via a facile solvothermal method, and investigated it removal performance towards Cr(VI). Under low pH condition, we found that the photogenerated electrons played a significant role in photocatalytic reduction of Cr(VI) verified through trapping experiment. Moreover, the more positive zeta potential of CaTiO3 after the completion of photocatalytic experiment was due to the existing trivalent chromium (Cr(III)) species. It could benefit the electrostatic attraction between anionic Cr(VI) species and the surface of CaTiO3. Meanwhile, the X-ray photoelectron spectroscopy (XPS) revealed that the Cr 2p peak of the photocatalytic treated sample was more apparent than that of the adsorption treated sample, indicating that large numbers of Cr species were loaded on CaTiO3 surface after the photocatalytic treatment. Herein, the surface reduced Cr(III) species on CaTiO3 played a positive role in the loading of Cr(VI) on CaTiO3 surface under low pH.