Properties and mechanism of hexavalent chromium removal by FeS@ graphite carbon nitride nanocomposites

Abstract

A novel nanocomposite, named as FCN, which was synthesized by loading FeS (Mackinawite) onto graphite phase carbon nitride (g-C3N4), was applied to remove Cr(VI) in aqueous solutions and characterized by SEM, BET, XRD, FTIR, Zeta and XPS. The effect of adsorption parameters including temperature, initial solution pH, FCN dosage, the initial concentration of Cr(VI), recycling performance of FCN and coexisting anions were investigated. Results revealed that the optimum adsorption capacity of the FCN for Cr(VI) was 61.8 mg/g at 298 K (pH = 3). Inorganic anions such as SO42−, NO3− and Cl− exhibited positive effect, while HCO3- inhibited the adsorption of Cr(VI). The adsorption kinetics of Cr(VI) followed the pseudo-second-order model and the adsorption process fitted the Langmuir model well. Thermodynamic results showed that the reaction process of FCN for Cr(VI) adsorption was an endothermic process with increasing entropy. The main mechanism of removing Cr(VI) by FCN were adsorption, chemical reduction and complexation. These results reveal that FCN will be a potential material for removing Cr(VI) from aqueous solutions.