Behavior Of Mn Research Articles

ECOLOGICAL AND GEOCHEMICAL FEATURES OF MANGANESE DISTRIBUTION IN GROUNDWATERS OF UKRAINE

The results of hydrogeochemical studies on the identification of the features of manganese distribution in drinking groundwater of conditionally clean and technologically polluted territories of Ukraine are presented, as well as the assessment of the influence of inorganic ligands characteristic of the investigated groundwater on the behavior of Mn2+ depending on the initial conditions of the water environment. The Kyiv city, as well as Zhytomyr, Vinnytsia, and Rivne regions were selected as conditionally clean territories; Kyiv and Dnipropetrovsk regions — as technologically polluted territories. According to domestic and foreign literary data, the range of medical, biological, and toxicological properties of manganese is outlined, and the key features of the element prevalence in natural aqueous solutions and underground waters are clarified. Manganese and ferrum concentrations in the samples of the studied groundwater were determined using the high-precision method of mass spectrometry with inductively coupled plasma (ICP-MS). As a result of the statistical processing of the studied samples, it was established that the median manganese content for most of the examined territories does not exceed the maximum permissible concentration. The exception is the underground water of the Pidhirtsi village (Kyiv region), where the concentration of the element exceeds the standard by almost 4 times. A comparative analysis to determine the relationship between the manganese and ferrum concentrations and the depth of water intake structures did not show any regularities characteristic of natural waters undisturbed by technogenic activity. It was revealed that the largest deviations from the background values for manganese are typical for the Dnipropetrovsk region, and for ferrum — for the Kyiv city. Statistically significant relationships between the concentrations of manganese and ferrum in the examined samples were not found, which indicates the different geochemical nature of the elements concentration processes in the studied groundwater. Using the specialized software tools Hydra and Medusa, the finding forms of manganese depending on the pH of the water environment in studied samples were calculated. The obtained ratios of the element soluble forms for conditionally clean and technologically polluted territories of Ukraine made it possible to establish that in the water of conditionally clean territories, manganese migrates mainly in the form of free Mn2+ ion, and to a much lesser extent (11%) in the form of MnSO4. On the other hand, within the technologically polluted territories, the key role belongs to the inorganic ligand SO42–, the ratio of soluble compounds MnSO4 and Mn2+ is, respectively, 56% to 44%. The obtained results can serve as a basis for the selection of criteria when performing biogeochemical zoning of the territory of Ukraine.

Features of the Behavior of Mn2+ Ions in the 3D Dirac Semimetal α-Cd3As2 from EPR Data

Features of the Behavior of Mn2+ Ions in the 3D Dirac Semimetal α-Cd3As2 from EPR Data

Efficacy of heat generation in CTAB coated Mn doped ZnFe2O4 nanoparticles for magnetic hyperthermia

Manganese doped Zinc ferrite (Mn–ZnFe2O4, where Mn = 0%, 3%, 5% and 7%) nanoparticles were synthesized by a simple co-precipitation method. CTAB (cetyltrimethylammonium bromide) was used as a surfactant to inhibitgrowth and agglomeration. In this work, we have discussed on the influence of CTAB and Mn doping in tailoring the structural and magnetic properties of Mn–ZnFe2O4 nanoparticles for the effective application of magnetic hyperthermia. X-ray diffraction (XRD) pattern confirmed the formation of cubic spinel structure of Mn–ZnFe2O4 nanoparticles. Lattice parameter and x-ray densities were obtained from the Rietveld refinement of the XRD pattern. The presence of CTAB as a stabilizing layer adsorbed on the surface of the nanoparticles were confirmed by transmission electron microscope (TEM) and Raman vibrational spectrum. The saturation magnetization showsan increasing trend with Mn addition owing to cationic re-distribution and an increase super-exchange interaction between the two sub-lattices. Superparamagnetic behaviorof Mn–ZnFe2O4 nanoparticles were confirmed by temperature-dependent zero-field-cooling (ZFC) and field-cooling (FC) magnetization curves. The efficiency of induction heating measured by its specific absorption rate (SAR) and intrinsic loss power (ILP) value varies as a function of saturation magnetization. It has been hypothesized that the maximum generation of heat arises from Neel relaxation mechanism. The optimum generation of heat of Mn–ZnFe2O4 nanoparticle is determined by the higher frequency (f = 337 kHz) range and maximum concentration of Mn doping.

Behavior of Mn2+ in perovskite manganites with nominal composition La0.6−x Nd x Sr0.1MnO3

The fact that there are Mn2+ at the A sites in the ABO3 perovskite phase of manganites with the nominal composition La0.6−xNdxSr0.1-MnO3 showed by detailed experimental study and theoretical calculations. The magnetic moments of these Mn2+ are antiparallel to those of the Mn ions at the B sites. The content of the Mn2+ increases as the average ionic radius, 〈rA〉, of the ions at A sites decreases, resulting in the experimentally observed phenomenon that the content of the Mn3O4 phase in the manganites decreases with decreasing 〈rA〉.

Photoluminescence of Mn2+ Centers in Chalcohalide Glasses

We report on photoluminescence from Mn2+-doped chalcohalide glasses of the GeS2–Ga2S3–CsCl system. Upon blue excitation at 447 nm, a broad emission band occurs in the green spectral range from 500 to 600 nm, indicating the presence of tetrahedrally coordinated Mn2+ species. When the Mn2+-concentration is increased up to 2 mol%, an increasingly intense secondary emission band evolves at about 610–660 nm. Meanwhile, the intensity of the green band decreases gradually and shifts toward the red, resulting a very flatten luminescence from 500 to 750 nm, which provides a promising white light emitting source. As for the origin of this unique luminescence behavior of Mn2+, it is proposed that the ligand coordination number of Mn2+ in the present chalcohalide glasses experiences a partial change from tetrahedral to octahedral coordination.

Distribution changes of Mn2+ and Fe3+ on weathered marble surfaces measured by EPR spectroscopy

The behavior of Mn2+ and Fe3+ on weathered marble surfaces was studied by electron paramagnetic resonance spectroscopy (EPR). The paper is concentrated in Mn2+ and Fe3+ replacing Ca2+ in the CaCO3 of marble. Nineteen marble samples of different types and exposed to different environmental conditions were analyzed: Samples of various grain sizes and manganese concentrations, samples from quarry fronts, excavations and monuments exposed in rural or polluted environments. Mn2+ does not show a systematic behavior but Fe3+ decreases up to 100% on the surface, compared to the marble bulk. The depletion starts at a depth around 4 mm from the outer surface. The phenomenon is explained by dissolution and re-crystallization of calcite together with microbe-mediated reduction of Fe3+ to Fe2+. Higher decrease is observed on samples of low-grade metamorphosis, on excavated samples and samples exposed to heavily polluted urban environment. Unexpectedly, this depletion extends deeper than the actual weathering depth (measured by SEM), i.e. the decrease in Fe3+ concentration extends beyond the patina–marble interface, up to a few millimeters into the healthy marble. This additional depletion may be explained by solid-state diffusion of iron. Such a hypothesis has already been reported in literature for other ions in calcite crystals.

Crystallization of Calcium Sulfite and Behavior of Mn2+

A small amount of manganese compound contained in limestone as an impurity takes an important role of a catalyst for the sulfite oxidation reaction. In the present work, it was found that Mn2+ coprecipitates with the calcium sulfite solid in a continuously-stirred tank reactor under the similar conditions as that in the absorber tank of the wet limestone scrubbing process. The experimental results indicated that the coprecipitaton ratio of Mn2+ to calcium sulfite solid increases linearly proportional to the dissolved Mn2+ concentration in the solution upto a critical Mn2+ concentration and remains constant in the range of higher Mn2+. It was also found that Mn2+ did not coprecipitate with gypsum crystal at all.

Spin glass behavior of Mn2+ ions in zeolite-Y at very low temperature

Magnetic properties of manganese ion spin systems in zeolite-Y have been measured. These ions act as almost free ions in the zeolite. Low frequency ac-susceptibility can be described with the Curie-Weiss law down to 50 mK. The susceptibility has a maximum around 30 mK showing a magnetic anomaly. Characteristic relaxation times deduced from frequency dependence of the maxima are studied. They diverge towardsTc = 0 K according to the following formula, τ = τ0exp{(b/T)ψυ+1} where τ0 = 3 x 10−10 sec, b = 0.28K, and ψν = 0.4, respectively. It is expected from ESR measurements that the dominant interaction between the manganese ions is dipole-dipole like. This divergence is interpreted as that of a dipolar spin glass.

Evidence for a spin-lattice relaxation process with two optical phonons : Mn2+ in ZnS

We have studied the spin-lattice relaxation behaviour of Mn2+ in cubic ZnS at 9 375 MHz between 80 K and 900 K by measuring the line broadening of the |1/2 1/2> → 1/2 - 1/2> transition. This study shows that for high temperatures (T > 273 K) the measured spin-lattice relaxation time T1 varies as T-11 = αT 7 I6 (θD) β[sh2 θ o T]-1. The first term corresponds to a Raman process associated with the acoustical phonons, the second one arises from the optical phonons distribution. The transition probabilities calculation shows that the contributions from the optical and acoustical phonons are similar.