Mossbauer Spectroscopy

In this work, the removal efficiency of U(VI) from water using commercial nanoparticles of zerovalent iron (nZVI) (NANOFER 25, NANO IRON s.r.o.) and magnetite (nM) (NanoFe®, Nanotek SA) was evaluated. Batch experiments were carried out in a jacketed reactor with a vertical paddle stirrer, using UO2(NO3)2 solutions([U(VI)]0 = 0.25 mM = 59.5 mg L-1) at pH 5.3. The nanoparticles (initially suspended in water) were added tothe U(VI) solution to achieve different Fe:U(VI) molar ratios (MR) in the range of 1 to 100. U(VI) removal with nZVI and nM at MR 4 and dissolved oxygen (DO) levels higher than 0.1 mg L-1 were rather efficient, reaching in both cases a final removal of 65 %. Under these conditions, uranium removal strongly depends on thepresence of DO, decreasing with increasing DO. When 40 and 100 MR were used, a complete U(VI) removal in the first 15 min of treatment was observed, and oxygen was consumed reaching negligible DO levels (below0.1 mg L-1). With MR = 4 and DO levels belo...

The cluster anion {Ge9[Si(SiMe3)3]3}– (1) is transferred intact into the gas phase via the electro spray method. Subsequently the fragmentation of 1 after resonant excitation as well as the oxidation reaction with O2 and Cl2 are investigated in an FT‐ICR mass spectrometer (Fourier Transform Ion Cyclotron Resonance). Unlike former results with off‐resonant excitation the fragmentation leads mainly to the end‐product Ge9–. Moreover, applying an on‐resonant excitation the dissociation experiment can be quantified; 2.0 ± 0.15 eV (193 ± 15kJ·mol–1) for the elimination of the first two ligands and 2.7 ± 0.15 eV (261 ± 15 kJ·mol–1) for all ligands, respectively. Particular attention is turned on the first step, where sterically encumbered Si2(SiMe3)6 molecules are formed in a concerted reaction. This result, which is also important for elemental reactions on metal surfaces in catalyses, is based on experimentally determined threshold energies, DFT calculations and calculations on the lifet...

Many of modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics, and polymeric materials. Material property combinations and ranges have been extended by the development of composite materials. Development of Nd-Fe-B/polymer composite magnetic materials has significantly increased interest in research and development of bonded magnets, since particles of Nd-Fe-B alloys are proved to be very suitable for their production. This study investigates the mechanical and magnetic properties of compression molded Nd-Fe-B magnets with different content of magnetic powder in epoxy matrix. Mechanical properties were investigated at ambient temperature according to ASTM standard D 3039-00. The obtained results show that tensile strength and elongation decrease with an increase of Nd-Fe-B particles content in epoxy matrix. The modulus of elasticity increases, which means that in exploitation material with higher m...

The present review describes our long experience in the application of Mössbauer spectroscopy with a high velocity resolution (a high discretization of the velocity reference signal) in the studies of various nanosized and nanostructured iron-containing materials. The results reviewed discuss investigations of: (I) nanosized iron cores in: (i) extracted ferritin, (ii) ferritin in liver and spleen tissues in normal and pathological cases, (iii) ferritin in bacteria, (iv) pharmaceutical ferritin analogues; (II) nanoparticles developed for magnetic fluids for medical purposes; (III) nanoparticles and nanostructured FINEMET alloys developed for technical purposes. The results obtained demonstrate that the high velocity resolution Mössbauer spectroscopy permits to excavate more information and to extract more spectral components in the complex Mössbauer spectra with overlapped components, in comparison with those obtained by using conventional Mössbauer spectroscopy. This review also sho...

Spirit's Mössbauer (MB) instrument determined the Fe mineralogy and oxidation state of 71 rocks and 43 soils during its exploration of the Gusev plains and the Columbia Hills (West Spur, Husband Hill, Haskin Ridge, northern Inner Basin, and Home Plate) on Mars. The plains are predominantly float rocks and soil derived from olivine basalts. Outcrops at West Spur and on Husband Hill have experienced pervasive aqueous alteration as indicated by the presence of goethite. Olivine‐rich outcrops in a possible mafic/ultramafic horizon are present on Haskin Ridge. Relatively unaltered basalt and olivine basalt float rocks occur at isolated locations throughout the Columbia Hills. Basalt and olivine basalt outcrops are found at and near Home Plate, a putative hydrovolcanic structure. At least three pyroxene compositions are indicated by MB data. MB spectra of outcrops Barnhill and Torquas resemble palagonitic material and thus possible supergene aqueous alteration. Deposits of Fe3+‐sulfat...

A new hybrid inorganic-organometallic salt has been obtained from the reaction of the Keggin-type silicotungstate anion with ferrocene in a water/methanol mixture as a result of the partial oxidation of ferrocene molecules to ferrocenium cations. Single-crystal X-ray diffraction analysis reveals the presence of four ferrocenium (FeIII) cations and one ferrocene (FeII) molecule per plenary Keggin anion in the crystal structure of [FeIII (Cp)2]4[SiW12O40]·[FeII(Cp)2]·2CH3OH (1). Compound 1 thus constitutes the first example in the literature in which ferrocenium and ferrocene species coexist in the structure of a polyoxometalate-based salt. The two crystallographically independent ferrocenium species in the asymmetric unit of 1 exhibit different configurations: One displays an eclipsed conformation with ideal D5h symmetry, whereas the conformation in the other one is staggered D5d. The crystal packing of 1 can be best described as an organometallic sub-lattice of ferrocenium and ferro...

Indigenous iron-oxidizing bacteria were isolated on modified selective 9KFe medium from Baiyin copper mine stope, China. Three distinct acidophilic bacteria were isolated and identified by analyzing the sequences of 16S rRNA gene. Based on published sequences of 16S rRNA gene in the GenBank, a phylogenetic tree was constructed. The sequence of isolate WG101 showed 99% homology with Acidithiobacillus ferrooxidans strain AS2. Isolate WG102 exhibited 98% similarity with Leptospirillum ferriphilum strain YSK. Similarly, isolate WG103 showed 98% similarity with Leptospirillum ferrooxidans strain L15. Furthermore, the biotechnological potential of these isolates in consortia form was evaluated to recover copper and zinc from their ore. Under optimized conditions, 77.68 ± 3.55% of copper and 70.58 ± 3.77% of zinc were dissolved. During the bioleaching process, analytical study of pH and oxidation-reduction potential fluctuations were monitored that reflected efficient activity of the bacte...

The electronic spin state of iron in lower mantle perovskite is one of the fundamental parameters that governs the physics and chemistry of the most voluminous and massive shell in the Earth. We present experimental evidence for spin-pairing transition in aluminum-bearing silicate perovskite (Mg,Fe)(Si,Al)O 3 under the lower mantle pressures. Our results demonstrate that as pressure increases, iron in perovskite transforms gradually from the initial high-spin state toward the final low-spin state. At 100 GPa, both aluminum-free and aluminum-bearing samples exhibit a mixed spin state. The residual magnetic moment in the aluminum-bearing perovskite is significantly higher than that in its aluminum-free counterpart. The observed spin evolution with pressure can be explained by the presence of multiple iron species and the occurrence of partial spin-paring transitions in the perovskite. Pressure-induced spin-pairing transitions in the perovskite would have important bearing on the magne...

Nanoscale mixtures of Ge/Sn, a nominally immiscible binary system, prepared by mechanical attrition have been studied by 119Sn Mössbauer spectroscopy. The Mössbauer measurements in general reveal two sites for the Sn atoms, a tetragonal β–Sn site and another site designated as “A”. The β-Sn integrated intensity decreases in magnitude with Ge concentration, 1 – x, in Ge1−xSnx as the second A-site intensity increases. The isomer shift and the small/negligible quadrupole splitting of site A suggests it represents Sn in solid solution in the Ge lattice. This in turn represents a large (12–24 at. %) nonequilibrium solid solubility of Sn in Ge prepared by mechanical milling, compared to the equilibrium value of <1.0 at. %. Oxidation of the Sn was detected by Mössbauer spectroscopy at Sn-poor concentrations (x ⋚ 0.10) when the milling vial was not totally free of oxygen (i.e., milling in impure argon). This may be due to rapid oxidation of finely divided Sn film particles possessing a l...