Theoretical Description for Omeprazole Cathodical Electrochemical Determination, Assisted by Omeprazole Electrochemical Determination, Assisted by the Composite Poly(1,2,4-triazole) – VO(OH)

In this work, we describe theoretically the possibility of omeprazole electrochemical determination, assisted by the composite containing vanadium oxyhydroxide as an active substance and the polymer of 1,2,4-triazolic derivative as a mediator. The omeprazole molecule undergoes a sulfoxide to sulfide reduction process over a trivalent vanadium compound. The vanadium oxyhydroxide, at its turn, may be oxidized to a tetravalent state, represented in two forms. The electroanalytical process behavior will be illustrated by a trivariate equation-set, analysis of which confirms the efficiency of the composite of poly (1,2,4-triazole) with VO(OH). Vanadium (III) oxyhydroxide may be efficiently used for omeprazole detection both in pharmaceutical formulations, food, and biological liquids.

BINDING d-ELEMENT OF THE 4TH PERIOD OF V-GROUP OF THE PERIODIC SYSTEM OF D.I. MENDELEYEV AND ITS PARAMAGNETIC PROPERTIES

Vanadium is a connecting element between the main subgroup VA and the subgroup VB. In the opinion of B.V. Nekrasov, if we compare the VВ group of vanadium elements with the valence states of P and Аs VА main subgroup, then in the oxidation states of -3, 0, +3 arsenic is an analogue of phosphorus, and in the oxidation state +5, it will not be an analogue of phosphorus. In contrast, in the low oxidation degrees of vanadium, it differs from phosphorus, and in the oxidation state of +5 vanadium is not a complete analogue of phosphorus. The similarity of the electronic configuration of atoms for vanadium and phosphorus in the +5 oxidation state specifies the similarity of the properties of their chemical compounds. When comparing vanadium and its compounds with elements of the VA subgroup, we conclude that vanadium is a binding element between the VA subgroup and the VB subgroup and the compounds have similar properties. As a result of many years of work, it was found that vanadium in the penta- and tetravalent states has paramagnetic properties. In crude oil, it is in a tetravalent state. In order to improve the standard photocalorimetric method for determining vanadium in oil and petroleum ashes, a more rapid method was proposed for estimating the total concentration of vanadium based on the interaction of V2O5 with concentrated hydrochloric acid. Studies of the EPR spectra of porphyrin complexes with transition metals such as copper were of great importance in the identification of natural porphyrin complexes. In the course of comparison of experimental works of paramagnetic properties of vanadium and phosphorus with each other, it can be said that their application is of great practical importance in different fields of science. Summing up the results of studying the reduction of triphenylphosphine with an alkali metal, we proposed a scheme for the splitting of triphenylphosphine, including the formation of radical anions.

Challenges in the Fabrication of Ceramic Technetium Waste Forms

ABSTRACTIn this research we can demonstrate, that fission technetium-99 can be successfully immobilized as tetravalent cation in solid state refractory oxides such as pyrochlores and perovskites. Pyrochlores show excellent performance in ASTM C1220-10 type corrosion testing and have the ability to structurally bond Tc-99 and therefore avoid the formation of highly-mobile, pertechnetate species under conditions of a generic repository. We have fabricated lanthanide technetium oxides using either dry-chemical ceramic processing, or wet-chemical coprecipitation methods. Tc pyrochlores have shown better Tc retention and corrosion resistance compared with Tc-containing LAWE4-type borosilicate glass, combined with 50-times higher waste loading. However, mechanical properties (fracture toughness, compressive strength) of the pyrochlores are lacking and the microstructure shows high open porosity of about 50 %. To improve these properties we tested a variety of measures such as hot-pressing or the combination of hot pressing and high-temperature synthesis, but the improvement was minor and Tc and the surrogate Ru were partly reduced. The presence of metallic inclusions has strong impact on Tc retention and release rates increased more than tenfold. We have further developed a wet-chemical coprecipitation synthesis route followed by calcination and a 4-days high-temperature sintering cycle for the model composition Sm2(Ru0.5Ti0.5)2O7 where titanium oxide was added as sintering agent. The ceramic surrogate waste forms showed improved theoretical densities of about 73 % combined with sufficient mechanical strength, while maintaining ruthenium in the tetravalent state.

Field effects on heterojunctions composed with electron-doped La1−xHfxMnO3 and Nb-SrTiO3 perovskites

Thin films and heterojunctions of Hf[Formula: see text]-doped LaMnO3 manganite have been studied. The sole tetravalent state of Hf[Formula: see text] ensures formation of [Formula: see text]-type La[Formula: see text]Hf[Formula: see text]MnO3 (LHMO) manganite. Photoinduced resistance was also observed as illuminated by visible light. The induced photoresistance (PR) could be greatly enhanced by the compressive strain. The LHMO/Nb-STO heterojunctions showed excellent rectifying characteristics, which are comparable with those [Formula: see text]-junctions of conventional semiconductors. Their transport properties are tunable electrically and magnetically. Such LHMO/Nb-STO heterojunctions have the potential to develop novel functional field-effect transistors based on manganite perovskites.

Uranium(IV) adsorption by natural organic matter in anoxic sediments

Uranium is an important carbon-free fuel source and environmental contaminant that accumulates in the tetravalent state, U(IV), in anoxic sediments, such as ore deposits, marine basins, and contaminated aquifers. However, little is known about the speciation of U(IV) in low-temperature geochemical environments, inhibiting the development of a conceptual model of U behavior. Until recently, U(IV) was assumed to exist predominantly as the sparingly soluble mineral uraninite (UO2+x) in anoxic sediments; however, studies now show that this is not often the case. Yet a model of U(IV) speciation in the absence of mineral formation under field-relevant conditions has not yet been developed. Uranium(IV) speciation controls its reactivity, particularly its susceptibility to oxidative mobilization, impacting its distribution and toxicity. Here we show adsorption to organic carbon and organic carbon-coated clays dominate U(IV) speciation in an organic-rich natural substrate under field-relevant conditions. Whereas previous research assumed that U(IV) speciation is dictated by the mode of reduction (i.e., whether reduction is mediated by microbes or by inorganic reductants), our results demonstrate that mineral formation can be diminished in favor of adsorption, regardless of reduction pathway. Projections of U transport and bioavailability, and thus its threat to human and ecosystem health, must consider U(IV) adsorption to organic matter within the sediment environment.

Electronic Chemical Properties of Vanadium Doped TiO2 for Photocatalytic Degradation of BTEX

V-doped TiO2(V-TiO2) was synthesised using solvothermal technique and immobilised onto fibreglass cloth (FGC). The XRD pattern of doped sample showed slight positive shift to higher angle indicating that the V ions were well substituted into the Ti lattices. The band-gap energy of V-TiO2was lower than that of P25, pure TiO2, (3.28 eV for P25 and 2.90 eV for V-TiO2) demonstrating it could be excited by visible light. The XANES spectra of the Ti K-edge transition indicated most Ti ions were in the tetravalent state with octahedral coordination. The A2species on the surfaces of V-TiO2were found to be the main active sites during photocatalytic degradation of BTEX under visible light irradiation.

Lithium Intercalation Properties of Lithium Tetratitanate Obtained by Nanosheets Process

Lithium intercalation properties of lithium tetratitanate obtained by nanosheets process (NS-LT4) was examined and compared with those of conventional lithium tetratitanate. NS-LT4 was prepared by restacking of tetratitanate nanosheets with LiOH aqueous solution. NS-LT4 exhibited a reversible capacity of approximately 140 mAh g-1, which corresponds to approximately two Li insertions per formula unit. Two Li insertions per formula unit mean that half of the Ti atoms were reduced from a tetravalent state to a trivalent state. The quasi open-circuit voltage of NS-LT4 was comparable with that of conventional lithium tetratitanate, and the voltage change of NS-LT4 as the change in lithium composition was greater than that of conventional lithium tetratitanate. This potential behavior would be caused by the unique stacking structure with stacking fault and random rotation in nanosheet-plane generated during the restacking of nanosheets.

Mössbauer-spectroscopic Characterization of the Local Surrounding of Tin Dopant Cations in the Bulk and on the Surface of YCrO3 Crystallites

119Sn Mössbauer spectra of tin-doped YCrO3, obtained by annealing in air of an YCr(119Sn4+)0.003(OH)6·xH2O precursor, provide evidence for the location of Sn4+ on the Cr3+ site in the bulk of crystallites. Below the Néel point of YCrO3 (TN = 141 K), Sn4+ ions are spinpolarized, the majority exhibiting a hyperfine field H of 80 kOe at 4.2 K. Analysis of the 119Sn spectra of another sample, obtained by impregnation of polycrystalline YCrO3 with a solution of 119SnCl4, shows that annealing in H2 results in the location of the dopant, in the divalent state, on the surface of the crystallites. The parameters of an in situ 119Sn spectrum at 295 K (isomer shift δ = 2.76 mm s−1 and quadrupole splitting EQ = 1.95 mm s−1) reveal the presence of Sn2+ ions on sites with a coordination number CN < 6. At 100 K these Sn2+ ions exhibit no spin polarization. Upon contact with air they are rapidly oxidized to the tetravalent state, as demonstrated by their modified isomer shift value δ = 0.06 mm s−1. For the large majority of both the residual “parent” Sn2+ ions and the “daughter” Sn4+ ones no spin polarization is observed down to 4.2 K. This means that surface-located tin dopant cations, regardless of their oxidation state, occupy the Y3+ sites with an equal number of Cr3+ neighbors having mutually opposite spin orientations.

Valence State of Ru at the Mn Sites in Pr0.5Sr0.5MnO3

Valence state of the doped Ru at the Mn sites in Pr 0.5 Sr 0.5 MnO 3 has been studied using Ru K-edge X-ray absorption near-edge structure (XANES) spectroscopy. In comparison with XANES of reference ruthenates, it is found that the Mn-site doped Ru is dominantly in tetravalent state. This result suggests that the change of charge carrier density by Ru doping is not sufficient to understand drastic enhancement of ferromagnetism observed in the transport properties of Ru-doped Pr 0.5 Sr 0.5 MnO 3. The prime role of Ru in Mn 3+– O – Mn 4+ networks is discussed in terms of the valency effect and the magnetic interactions between doped Ru and Mn ions.

Pu-Th separation studies employing di(2-ethylhexyl)isobutyramide (D2EHIBA) as extractant from nitric acid medium

SummaryAn attempt has been made to explore the use of di(2-ethylhexyl)isobutyramide (D2EHIBA) as an extractant for the recovery of Pu from the (proposed) AHWR fuel fabrication scrap solution. The extraction of Pu in the hexavalent state has been found to be distinctly more efficient than that in the tetravalent state. Distribution studies have been carried out by maintaining Pu as Pu(VI) employing AgO as the oxidant. Scrubbing at 5M HNO