Green synthesis of graphene oxide-MnFe2O4 composites and their application in removing heavy metal ions

The composites of graphene oxide (GO) decorated by MnFe2O4 have been synthesised via a green and facile strategy that the pristine GO/MnSO4 suspension prepared by Hummers method was directly utilised to convert into the GO-MnFe2O4 composites. The as-prepared composites were characterised using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectra and X-ray photoelectron spectroscopy. The results indicated that the GO-MnFe2O4 composites were successfully synthesised. The removal behaviours of Pb2+ and Cu2+ onto GO-MnFe2O4 were investigated, which indicated that the composites exhibited great adsorption property in aqueous solution. The adsorption process could be fitted well by the pseudo-second-order model and Langmuir isotherm. The thermodynamic studies indicated that the adsorption process of Pb2+ and Cu2+ onto GO-MnFe2O4 composites was spontaneous and endothermic in nature. Furthermore, the maximum adsorption capacities for Pb2+ and Cu2+ calculated from Langmuir model were about 263.85 and 103.41 mg/g at 318 K, respectively. Based on the results from the reusability experiments, the as-prepared GO-MnFe2O4 composites could be used as a potential adsorbent for removing Pb2+ and Cu2+ ions from aqueous solutions.