Wheat-Flour-Derived Magnetic Porous Carbons by CaCl2-Activation and their Application in Cr(VI) Removal

Magnetic porous carbons were obtained from wheat flour via simple one-step pyrolysis employing calcium chloride as activator. A series of wheat flour derived-magnetic porous carbons (WMCs) with various pyrolysis temperature and precursor were prepared, characterized and applied for Cr(VI) removal. The results show that gamma-FeOOH and Fe3O4 were respectively obtained in the WMCs at pyrolysis temperature above and below 600 degrees C. While, the calcium chloride enhanced the mesoporous of WMCs and promoted the crystallization of Fe3O4. The optimal sample exhibited super Cr(VI) removal capacities of 15.53 mg g(-1) and good reusability after 5 recycles in neutral solution. The Cr(VI) removal of WMCs obeys pseudo-second-order adsorption model and Langmuir adsorption isotherms. The enhanced adsorptivity can be attributed to the incorporation of adsorption and reduction reaction between Cr(VI) ions and Fe3O4. The density functional theory calculations also demonstrated that Cr(VI) ions is more favorable and strongly adsorbed onto Fe3O4 surface than gamma-FeOOH.