Effects of Co doping on the structure and physicochemical properties of hausmannite (Mn3O4) and its transformation during aging

Hausmannite is a common low-valence manganese oxide mineral with distorted spinel structure in surficial sediments. Although natural Mn oxides often contain various transition metal (TM) impurities, few studies have addressed the substitution mechanisms of TMs, such as cobalt (Co), hausmannite and induced changes physicochemical properties. In this study, Co-doped hausmannites final Co/Mn molar ratios 0.05 0.11 were synthesized characterized by wet chemical analysis, powder X-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR), high resolution transmission electron microscope (HRTEM), photoelectron spectroscopy (XPS) absorption fine (XAFS). samples larger crystallite sizes smaller specific surface areas than those without Co. The Co cations exist mixed-valence +3 + 2. Powder XRD acid dissolution experiments indicate that incorporates into structures, increases structural stability. K-edge extended adsorption (EXAFS) analysis demonstrates likely substitutes for lattice Mn(III). After aging at room temperature three years, 14.1 ± 1.9% pure to manganite while only 2.6 0.7% appears aged sample an initial ratio 0.10. These results provide new insights incorporation TMs low valence oxides, stability these minerals environments.