Carbothermal synthesis of ordered mesoporous carbon-supported nano zero-valent iron with enhanced stability and activity for hexavalent chromium reduction

Composites of nano zero-valent iron (nZVI) and ordered mesoporous carbon (OMC) are prepared by using simultaneous carbothermal reduction methods. The reactivity and stability of nZVI are expected to be enhanced by embedding it in the ordered pore channels. The structure characteristics of nZVI/OMC and the removal pathway for hexavalent chromium (Cr(VI)) by nZVI/OMC are investigated. Results show that nZVI/OMC with a surface area of 715.16 m(2) g(-1) is obtained at 900 degrees C. nZVI with particle sizes of 20-30nm is uniformly embedded in the OMC skeleton. The stability of nZVI is enhanced by surrounding it with a broad carbon layer and a little gamma-Fe is derived from the passivation of alpha-Fe. Detection of ferric state (Fe 2p(3/2), around 711.2 eV) species confirms that part of the nZVI on the outer surface is inevitably oxidized by O-2, even when unused. The removal efficiency of Cr(VI) (50 mg L-1) by nZVI/OMC is near 99% Reduction within 10 min through reduction (dominant mechanism) and adsorption. nZVI/OMC has the advantage in removal efficiency and reusability in comparison to nZVI/C, OMC and nZVI. This study suggests that nZVI/OMC has the potential for remediation of heavy metal pollution in water. (C) 2015 Elsevier B.V. All rights reserved.