Novel highly reactive and regenerable carbon/iron composites prepared from tar and hematite for the reduction of Cr(VI) contaminant.

Highly reactive carbon/Fe composites were prepared from tar used as a carbon source, and hematite (alpha-Fe(2)O(3)), a widespread naturally available iron oxide. Tar was impregnated on hematite and thermally treated under N(2) atmosphere. Mössbauer, powder X-ray diffraction and magnetization data suggested that treatment at 400 and 600 degrees C produced only magnetite (Fe(3)O(4)) whereas at 800 degrees C mainly metallic iron (Fe(0)) was produced. Raman, TG and XRD analyses of the different composites revealed the presence of amorphous and graphitic carbon highly dispersed on the iron oxide surface. The composites obtained at 800 degrees C were very efficient in reducing aqueous Cr(VI), as CrO(4)(2-), even compared to finely ground commercial Fe(0). XPS and Mössbauer data showed that after five consecutive reuses, the composites deactivated, due to the surface oxidation of Fe(0). A simple treatment at 800 degrees C completely regenerated the composite by reducing Fe(3+) species allowing several reuses.