The exploration of a new adsorbent as MnO2 modified expanded graphite

MnO2-modified Expanded Graphite (MnO2/EG) nano-composites were prepared through redox-precipitation reaction between EG, MnSO4 solution and KMnO4 solution at 40 °C. The X-ray powder diffraction (XRD) results showed that the surface of EG was grafted with γ-MnO2. Meanwhile, a Field Scanning Electron Microscope (FSEM) was employed to analyze the morphology of the as-modified expanded graphite. Nano spindles (with a length of 30–80 nm and a diameter of 10–30 nm) were observed on the surface and interspaces of EG. Fourier transform infrared (FTIR) spectra verified the presence of new functional groups on the surface of the MnO2/EG which were not seen on EG. The superior adsorbent properties of the as-synthesized MnO2/EG proved highly effective in absorbing Cr(VI), where the removal rate reached 90.35% and the absorbed amount reached about 0.3011 mg/g. Improved properties for adsorbing Cr(VI) from polluted water were observed in MnO2/EG, and the absorbed amount at equilibrium was more than twice as much as that of EG.