Synthesis and characterization of magnetic-montmorillonite and magnetic-organo-montmorillonite: Surface sites involved on cobalt sorption

Abstract

Montmorillonite magnetic-clay nanoparticles (MtMag) and its exchanged product with hexadecyltrimethylammonium (O100MtMag) were synthetized by alkaline oxidation of ferrous sulfate, characterized by diverse techniques (XRD, Mössbauer spectroscopy, VSM, SEM, Zeta Potential, total specific surface area, TOC) and used as Co2+ sorbents. The magnetic characteristic of these materials allows them to be used in cases of decontamination of water polluted with dangerous materials, such as radioactive ones, reducing the risk to health due to indirect manipulation by means of external magnetic fields. For comparison, samples without magnetic material (O100Mt) and in absence of clay (Mag) were also synthetized. The synthesis of magnetic materials disclosed the presence of magnetite and goethite nanoparticles, while the saturation magnetization displayed by O100MtMag was higher than that obtained for MtMag, indicating the existence of a higher amount of magnetite particles in the first one. This suggests that O100MtMag could be manipulated easier than MtMag through external magnetic fields. Moreover, the surface electric charge of MtMag sample can be described as a mixture of Magnetite and montmorillonite, with ratios related to the surface of both components. Co2+ sorption percentages, using an initial Co2+ concentration of 85 mg/L, resulted similar for the different materials while the Co2+ sorption was ascribed to interactions with the montmorillonite interlayer and external surface. The current results indicate that O100MtMag is a more appropriate material than MtMag for Co2+ removal by external magnets.