Fe3O4–wheat straw: preparation, characterization and its application for methylene blue adsorption

The removal of methylene blue (MB) from aqueous solution by NaOH-treated wheat straw from agriculture biomass impregnated with Fe3O4 magnetic nanoparticles (MNP-NWS) was investigated. Magnetic nanoparticles (Fe3O4) were prepared by chemical precipitation of a mixture of Fe2+ and Fe3+ salts from solution aqueous by ammonia. These magnetic nanoparticles of the adsorbent Fe3O4 were characterized by Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), nitrogen physisorption and Fourier Transform Infrared Spectroscopy (FTIR). FTIR results showed complexation and ion exchange appears to be the principal mechanism for MB adsorption. The adsorption isotherm data were fitted to Langmuir, Sips, Redlich–Peterson and Freundlich equations. Langmuir adsorption capacity, Qmax, was found to be 1374.6 mgg−1. The Freundlich equation yielded the best fit to the experimental data in comparison to the other isotherm models. The removal of MB by MNP-NWS followed pseudo-first-order reaction kinetics based on Lagergren equations.