Synthesis of novel magnetic activated carbon for effective Cr(VI) removal via synergistic adsorption and chemical reduction

The removal of a toxic contaminant like Cr(VI) from the water via green adsorbents like biochar and activated carbon is an eco-friendly technique. In this paper, using commercial activated carbon as a raw material, magnetic ferric oxide/activated carbon (Fe3O4@AC) was prepared by the chemical co-precipitation method, and Cr(VI) adsorption in water was applied. The synthesized materials were characterized by advanced characterization techniques including XRD, BET, FT-IR, and XPS. The effects of initial Cr(VI) concentration, temperature, and adsorption time on the adsorption effect of Cr(VI) were evaluated. Results illustrated that the maximum Cr(VI) adsorption achieved by Fe3O4@AC was 45.3 mg/g, with a removal rate of 88.8% at the optimum pH of 2.0 and an adsorption time of 12 h. Under these conditions, Cr(VI) adsorption by Fe3O4@AC fits the pseudo-second-order kinetic model (PSO) and Langmuir isotherm model and is a spontaneous, endothermic, and irreversible process. The results of BET, XRD, FT-IR, and XPS characterization analysis of Cr(VI) before and after adsorption suggested that the adsorption mechanism of Fe3O4@AC is mainly based on chemisorption, supplemented by physical adsorption, accompanied by electrostatic attraction and complexation.