Synthesis of manganese dioxide/iron oxide/graphene oxide magnetic nanocomposites for hexavalent chromium removal

Abstract

Effective removal of heavy metal ions from wastewater is one of the important environment issues. Here, manganese dioxide/iron oxide/graphene-based magnetic nanocomposites (MnO₂/Fe₃O₄/graphene oxide and MnO₂/Fe₃O₄/graphene) were prepared by an easy and effective two-step reaction and investigated for the removal of hexavalent chromium ion from water. The materials were characterized by transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and Brunauer–Emmett–Teller surface area measurement. MnO₂/Fe₃O₄/graphene oxide (MnO₂/Fe₃O₄/GO) synthesized at pH 5.0 was the most effective adsorption material among other samples synthesized under different conditions. The Langmuir isotherm model was consistent with the experimental data at different pH values. MnO₂/Fe₃O₄/GO showed excellent adsorption capacities both at pH 5.0 (q_max = 175.4 mg g⁻¹) and pH 2.0 (q_max = 193.1 mg g⁻¹). Hexavalent chromium adsorption by MnO₂/Fe₃O₄/GO was pH dependent. The adsorption kinetic data were best described by a pseudo-second-order model. MnO₂/Fe₃O₄/GO was stable and easily recovered. These experimental results suggested that MnO₂/Fe₃O₄/GO had great potential as an economic and efficient adsorbent of heavy metals from wastewater.