Hematite reaction with tar to produce carbon/iron composites for the reduction of Cr(VI) contaminant

Abstract

In this work, highly reactive carbon–iron composites were prepared using a waste, i.e. tar, as carbon precursor and a simple iron oxide, i.e. hematite. Tar was impregnated on Fe2O3 with different tar/hematite weight ratios of 1:1; 2:1 and 4:1, and thermally treated under N2 atmosphere (400°C, 600°C and 800°C). Mössbauer, XRD and magnetization measurements suggested that treatment at 400°C and 600°C produces Fe3O4 but treatment at 800°C produced mainly Fe°. Raman and TG analyses of the different composites suggested the formation of carbon contents of 18, 24 and 32 wt.% as amorphous and graphitic highly dispersed on the Fe surface. The composites obtained at 800°C showed high efficiency to reduce Cr(VI) as CrO 2−4 in aqueous medium with much better results compared to finely ground commercial Fe°.