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 m2/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), N2 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 μmol (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.