Synergistic effect of iron doped ordered mesoporous carbon on adsorption-coupled reduction of hexavalent chromium and the relative mechanism study

•Iron doped ordered mesoporous carbon (Fe/CMK-3) was applied as a novel remediation material to remove hexavalent chromium (Cr(VI)).•A high capacity for the removal of Cr(VI) was observed.•Cr(VI) removal was an adsorption-coupled reduction process by Fe/CMK-3.•Fe/CMK-3 showed good magnetic separation performance and excellent reproducibility.

In this study, a magnetic iron nanoparticles doped ordered mesoporous carbon (Fe/CMK-3) was successfully prepared for highly effective removal of Cr(VI). The resultant carbon material maintained ordered mesostructure, high surface area of 679.4 m2 g−1 with 4.42 wt% magnetic nanoparticles (Fe0, Fe3O4 and λ-Fe2O3) inside, and excellent magnetic property. Batch experiments were conducted to investigate the removal performance. Fe/CMK-3 exhibited higher Cr(VI) removal efficiency (∼97%), broader pH scope of application and easier separation compared with pristine ordered mesoporous carbon (CMK-3). The kinetics data were well described by pseudo-second-order kinetic model, and Langmuir model fitted the sorption isotherms commendably. Moreover, the Cr loaded Fe/CMK-3 could be regenerated by 0.01 mol L−1 NaOH solution, and the removal capacity decreased by ∼22% in the seventh cycle. X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the Cr(VI) removal was a adsorption and synergistic reduction process owing to trivalent chromium Cr(III) occurring on the surface of Fe/CMK-3. The results suggested that Fe/CMK-3 had potential superiority in removal of Cr(VI) from wastewater.

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