Synthesis and characterization of robust zero valent iron/mesoporous carbon composites and their applications in arsenic removal

Nanoscale zero valent iron particles (nZVI) have been developed by in situ reduction of Fe3+ ions onto a mesoporous type of carbon matrix - Starch-Derived Mesoporous Carbonaceous Material previously reported and marketed commercially as Starbon''. The obtained nZVI/Starbon hybrid material exhibits homogeneous distribution of nZVI (10-20 nm) within the carbon matrix, surface area of 141 m(2)/g and a total iron loading of 1 mmol per gram of the composite, in accordance with transmission electron microscopy (TEM), X-ray diffraction (XRD), N-2 adsorption-desorption measurements, Infrared (IR)/Raman spectroscopy and Thermal gravimetric (TG)/Differential Thermal analysis (DTA). Electron Paramagnetic Resonance (EPR) and proton binding measurements show that the nanoparticles have a core-shell structure with iron(III) oxide/hydroxide shell due to partial air-oxidation of nZVI and the composite exhibits four different types of proton binding groups. Most importantly, the nZVI/Starbon hybrid has been tested as absorbent for As(III) removal showing a total removal of 358 mu mol (26.8 mg) of As(III) per gram of the composite at pH = 7. We also discuss the principal role of surface OH groups of iron oxide in arsenic uptake and the crucial effect of pH on removal efficiency. (C) 2015 Elsevier Ltd. All rights reserved.