Structure and Properties of Nanosized Composites Based on Fe3O4 and Humic Acids

Abstract

Nanocrystalline composite materials based on magnetite Fe₃O₄ and humic acids (HA) were synthesized and characterized. Investigation of these materials by EPR, fluorescence spectroscopy, electron microscopy, and XRD analysis showed that the surface of magnetite nanoparticles was densely covered with HA molecules, the size of the Fe₃O₄ nucleus decreasing when the HA : Fe₃O₄ ratio increased. An EPR study showed that the structure of the ferromagnetic magnetite nanoparticles changed at increased HA contents. The IR and fluorescence spectroscopy data suggest active participation of carboxyl and hydroxyl groups of HA in the adsorption of HAs on the Fe₃O₄ surface. The main types of interaction of Fe₃O₄ with HA were considered, and a scheme of possible chemical reactions was proposed.