Mössbauer spectroscopy of composites based on the bentonite-magnetite system

The properties of iron-containing bentonites synthesized by chemical coprecipitation from aqueous solutions of iron salts have been studied. To characterize the synthesized composites, Mössbauer spectroscopy, X-ray diffraction and magnetic measurements were used, the results of which were determined by the content and valence state of iron ions localized in the structure of bentonites, as well as the composition of inclusions of iron-containing compounds. Structural features and their relationship with magnetic properties for a mixture of iron oxides and bentonite-iron oxide composites were studied using Mössbauer spectroscopy methods. As a result of the synthesis, composite powder materials based on bentonite and ferromagnetic oxides Fe3O4 and γ-Fe2O3 were obtained. It has been established that when moving from an oxide mixture powder to a bentonite-iron oxide composite, the values of remanent magnetization and saturation magnetization decrease significantly, while for magnetic parameters determined by crystallographic anisotropy and anisotropy of particle shape, the opposite trend is observed. It has been shown that the magnetic properties of bentonite-based composites depend on the nature of the localization of iron oxides and the ratio of their concentrations. Localization of Fe2+ ions in the bentonite structure was discovered near oxygen vacancies forming octahedral positions.