Immobilization of Cr(VI) from solution by a graphene oxide-nZVI/biochar composite

A graphene oxide (GO)-nanoscale zerovalent iron (nZVI)-biochar composite (GO-nZVI/BC) was synthesized prior to characterization by X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy analyses. Batch experiments were performed at different initial Cr(VI) concentrations, contact times, and solution pH values. The effects of coexisting anions and chelating agents were also examined. The results indicated that the removal of Cr(VI) was highly pH-dependent and reached a maximum capacity at pH of 2. The equilibrium data were fitted well with the Langmuir isotherm model, and the kinetic data fitted better with the pseudo-second-order kinetic model. The increasing concentrations of EDTA in aqueous solutions were favorable to the removal of (XVI), while NO3- significantly inhibited adsorption. Furthermore, the GO-nZVI/BC maintained similar to 84.5% of its original capacity after aging in the air for 25 weeks. Based on the removal efficiency, GO-nZVI/BC can be considered to be an effective material for water treatment applications. (C) 2019 Water Environment Federation