Phytofabrication of Fe~0/Fe_3O_4 Composites for the Removal of Hexavalent Chromium

摘要

The leaf extract of pomegranate (Punica granatum) was used for the partial reduction of iron species to zerovalent iron (Fe~0). After alkali treatment, the presence of Fe~0/Fe_3O_4 composites was confirmed by a variety of analytical techniques. These composites were used for the detoxification of hexavalent chromium [Cr(VI)] ions. Maximum Cr(VI) reduction was observed at pH 2.0 and at a temperature of 40℃. There was a direct relation between Cr(VI) removal capacity and nanocomposite content as well as the initial metal concentration. Maximum specific uptake value (76.5 ± 3.2 mg/g) was obtained when 4.0 g/liter of composites were treated with 500 mg/liter Cr(VI) ions at pH 2.0 and 40℃. The data fitted to the Langmuir and Freundlich isotherms indicating the role of adsorption in the process of Cr(VI) reduction. The composites were significantly effective in Cr(VI) removal up to six cycles. X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis indicated the formation of goethite [FeO(OH)] after recurrent Cr(VI) exposure. The phytofabricated Fe~0/Fe_3O_4 composites were thus effective in Cr(VI) detoxification.