Enhanced photocatalytic reduction of Cr(VI) from aqueous solution using Fe⁰/TiO₂-based polymeric nanocomposites

The combination of zerovalent iron (Fe⁰) and titanium dioxide (TiO₂) has been investigated as a promising method for environmental remediation. However, it is a challenge to prepare conveniently desirable Fe⁰/TiO₂ nanocomposites with excellent efficiency and reusability. Here, a novel nanocomposite material, Fe⁰/TiO₂@D201, was synthesized to enhance the removal of Cr(VI) from an aqueous system by impregnating Fe⁰ and TiO₂ inside a commercial anion exchanger (D201). The proposed structure and Cr(VI) removal mechanism of Fe⁰/TiO₂@D201 were confirmed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Compared to the monometallic samples (Fe⁰-D201 and TiO₂-D201), Fe⁰/TiO₂@D201 showed outstanding Cr(VI) removal and the removal ratio reached up to 97.30% after 120 min of UV light irradiation. The removal of Cr(VI) by Fe⁰/TiO₂@D201 remained high (91.70%) even after four cycles, indicating the stability of the nanocomposites toward Cr(VI) removal and their strong potential for practical applications. The addition of ethylenediaminetetraacetic acid (EDTA) positively affected the Cr(VI) reduction process, whereas the addition of Na₂S₂O₈ negatively affected the Cr(VI) process. The XPS results revealed that the photocatalytic reduction of Cr(VI) by Fe⁰/TiO₂@D201 involved the capture of photoexcited electrons and Fe⁰ reduction. A path for the photogenerated electrons engaging in the reduction reaction to improve the utilization of Fe⁰ was proposed. These results demonstrate that Fe⁰/TiO₂@D201 is a promising alternative composite catalyst for the efficient Cr(VI) removal from contaminated water.