Synthesis, physical properties and application of the zero-valent iron/titanium dioxide heterocomposite having high activity for the sustainable photocatalytic removal of hexavalent chromium in water

Abstract

A magnetic photocatalytic material composed of nanoscale zero-valent iron (nZVI) homogeneously distributed over a mesoporous nanocrystalline TiO₂ matrix has been prepared by a multistage chemical process, including sol–gel technique, wet impregnation, and chemical reduction. X-ray powder diffraction and Raman spectroscopy were used for the structural and chemical characterization of the magnetic photocatalyst, while bulk magnetization measurements and scanning/transmission electron microscopy were employed to determine the physical and textural properties of the photocatalyst. The synthesized nZVI@TiO₂ photocatalyst shows very high efficiency in the removal of hexavalent chromium, Cr(VI), from water. The degradation rate follows a pseudo-first-order kinetic model. Most importantly, the remarkable efficiency of the photocatalyst is found to be due to the synergistic contributions of both counterparts, nZVI and TiO₂, as validated by comparative experiments with neat TiO₂ and nZVI@TiO₂ under UV-C irradiation and without irradiation. New insights into the mechanism of synergistic degradation of chromium(VI) and suppressed oxidation of nZVI particles in the composite material are proposed and therein discussed.