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In this study, nano-sized particles of manganese oxyhydroxide (MnO(OH)) are synthesized. Sorption properties of this material towards 90Sr and 137Cs radionuclides in the pH range from 2 to 9 at a temperature of 293.15 K solution are studied. The time of sorption achievement equilibrium in the radionuclide sorbent system depends on the nature of sorbed cation, but does not exceed 60 min. [ABSTRACT FROM AUTHOR]

The early nucleation stage of Mn (hydr)oxide on mineral surfaces is crucial to understand its occurrence and the cycling of nutrients in environmental systems. However, there are only limited studies on the heterogeneous nucleation of Mn(OH)2(s) as the initial stage of Mn (hydr)oxide precipitation. Here, we investigated the effect of pH on the initial nucleation of Mn(OH)2(s) on quartz. Under various pH conditions of 9.8, 9.9, and 10.1, we analyzed the structural matches between quartz and heterogeneously nucleated Mn(OH)2(s). The structural matches were calculated by measuring the lateral and vertical dimensions using grazing incidence small angle X-ray scattering and atomic force microscopy (AFM), respectively. We found that a poorer structural match occurred at a higher pH than at a lower pH. The faster nucleation under a higher pH condition accounted for the poorer structural match observed. By fitting the structural match using classical nucleation theory, we also calculated the interfacial energy between Mn(OH)2(s) and water: γnf = 71 ± 7 mJ/m². The calculated m values and γnf provided the variance of interfacial energy between quartz and Mn(OH)2(s): γsn = 262-272 mJ/m². This study provides new qualitative and quantitative information on heterogeneous nucleation on an environmentally abundant mineral surface, quartz, and it offers important underpinnings for understanding the fate and transport of trace ions in environmental systems. [ABSTRACT FROM AUTHOR]

The article discusses the study which focuses on the intranasal delivery of manganese hydroxide nanoparticles in brain structure. The use of the magnetic resonance imaging (MRI) in determining the neuronal transport of the brain is mentioned. The evaluation the olfactory bulb region is noted, along with the analysis of paramagnetic nanoparticles.

Highlights: [•] We report on the synthesis of phases in the Mn oxi-hidroxyde system in supercritical water. [•] Acetates were employed as precursors and only two high pressure pumps were used. [•] Synthesis conditions have been optimized concerning the flow rate and temperature. [•] Monodispersion and shape of nanoparticulated samples are characterized. [Copyright &y& Elsevier]

The structure and properties of nanodisperse manganese oxides obtained under conditions of an external electric field are studied using transmission and scanning electron microscopy, X-ray diffraction analysis, thermic analysis, and atom-emission spectroscopy. The influence of synthesis conditions on formation of structure and morphology of nanoparticles is studied. It is shown that effect of electric field on reaction media allows us to control the physicochemical properties and morphology of manganese oxide. [ABSTRACT FROM AUTHOR]

Manganese (hydr)oxides (MnO) is a powerful oxidant in the oxidation of As(III) in natural environment. Under some circumstances, Mn(II) can be oxidized to MnO which in turn accelerates the oxidation of As(III). However, to the best of our knowledge, little is known regarding how Mn(II) affects the oxidation of both the dissolved and the adsorbed As(III) in aquatic environments. In this study, effects of abiotic oxidation of Mn(II) on the oxidation of As(III) were investigated. Kinetic results as well as TEM and XRD analyses confirmed the formation of amorphous MnO after sorption of Mn(II) on hematite nano-particles under oxic conditions. Mn(II) was oxidized to Mn(III) and then to Mn(IV), and this process was dependent upon pH and Mn(II) concentrations. The newly formed MnO played an important role in the further oxidation of the dissolved and the adsorbed As(III) on hematite, and the oxidation rate of As(III) increased with the rising Mn(II) concentrations. As the adsorbed As(III) was oxidized to As(V), a fraction of As(V) was released into the solution, which increased the mobility of As. The present study reveals that abiotic oxidation of Mn(II) affects the oxidation of As(III) in aquatic environment. [ABSTRACT FROM AUTHOR]