Carbothermal preparation of porous carbon-encapsulated iron composite for the removal of trace hexavalent chromium

Porous carbon-encapsulated iron (Fe@PC) composite was prepared through carbothermal reduction of Fe(NO3)(3) and starch. The porous carbon could envelop iron and protect it from being oxidized, while iron endow the composite with ferromagnetism, so that Fe@PC can be easily recovered by an external magnetic field. The prepared material was used to remove trace Cr(VI) in polluted water. The Cr(VI) removal process of Fe@PC, which highly depended on both microporous structure and reducing groups, was significantly affected by the preparation conditions and solution pH. At 25 degrees C, Fe@PC-750 could remove 99.5% Cr(VI) from simulated wastewater containing 5.00 mg L-1 Cr(VI) with an initial pH of 7, and the residual concentration of Cr(VI) was as low as 0.02 mg L-1. The XPS analysis results confirmed that Cr(VI) could be reduced to Cr(III) after being adsorbed, and the elevation of pH would enhance the reduction ability of Fe@PC. The Fe@PC composite with high Cr(VI) removal efficiency, strong magnetic property and desirable regeneration ability can be practically applied in the removal of trace heavy metal pollutants from wastewater. (C) 2014 Elsevier B.V. All rights reserved.