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Nature-inspired synthesis of magnetic non-stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic medium

Change of color of the solutions during synthesisNature-inspired synthesis of magnetic non-stoichiometric Fe3O4 nanoparticles by oxidative in situ method in a humic medium. Pankratov D.A., Anuchina M.M. //Materials Chemistry and Physics. 2019. V.231. P.216-224.

Magnetic iron oxide nanoparticles in humic substances shell - Fe3-δO4@HS were synthesized by oxidative in situ method in aqueous solutions of humic substances from metallic iron precursor. Humic substances interacting with metallic iron under natural conditions act as a complex reagent that participates in acid-base, redox, complexation reactions and adsorption processes. The Fe3-δO4@HS particles is the final product of corrosion of metallic iron in the presence of HS. Products were characterized by dynamic light scattering, scanning and transmission electron microscopy, X-ray powder diffraction, Mössbauer spectroscopy, magnetometry, infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and evolved gas analysis. It was demonstrated that the samples contained particles with sizes of 40–50 nm comprised of ∼24 nm magnetite-like crystalline cores coated by humic substances. The synthetic approach used in this article can be used as a model of corrosion processes of ferrous metals in nature. In addition, magnetite-like nanoparticulates stabilized with humic substances can be promising as bioavailable iron additives for agricultural applications.

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Sorption of humic substances on a weakly basic anion-exchange resin: Relationship with the adsorbate structure

Experimental data on the sorption of HS on ANS anion-exchange resin and respective theoretical isotherms in terms of (1) the BET and (2–7) Langmuir models: (solid lines) commercial preparations (1) CHS, (3) LH, and (5) CHP and (dashed lines) desalted samples (2) CHA-SH, (4) LHA, (6) PHF, and (7) PHASorption of humic substances on a weakly basic anion-exchange resin: Relationship with the adsorbate structure. Pankratov D.A., Anuchina M.M., Borisova E.M., Volikov A.B., Konstantinov A.I., Perminova I.V. //Russian Journal of Physical Chemistry A. 2017. V.91. №6. P.1109-1115.Search the full text below. Ищи полный текст ниже.

Adsorption of a broad range of humic substances (HS) of different origins and fractional compositions on a macroporous weakly basic anion-exchange resin is studied. It is found that the nature of the humic substances has a substantial effect on both the efficiency of sorption and the mechanism of interaction with the adsorbent. The dependence of the determined thermodynamic parameters of sorption on the humic substances origin, composition, and structure is shown for a broad range of humic substances. It is concluded that the results can be used to predict the sorption properties of weakly basic anion-exchange resins with respect to humic substances of known origin and structural group composition.

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Properties of Iron-Containing Nanohydroxyapatite- Based Composites

EPR spectra of the (a) N-a and (b) N-c samplesProperties of Iron-Containing Nanohydroxyapatite-Based Composites. Pankratov D.A., Dolzhenko V.D., Ovchenkov E.A., Anuchina M.M., Severin A.V. //Inorganic Materials. 2017. V.53. №1. P.89-98.Search the full text below. Ищи полный текст ниже.

The paramagnetic properties of compounds resulting from the synthesis of nanohydroxyapatite in the presence of Fe(III) ions have been studied by electron paramagnetic resonance, Mössbauer spectroscopy, and magnetochemistry. Based on the obtained results on the mechanism of the reaction between an orthophosphoric acid solution and an aqueous calcium hydroxide suspension, we have found conditions for incorporating Fe(III) impurity ions into hydroxyapatite. We have studied samples differing in the sequence in which reagents were mixed and in hydroxyapatite crystallite formation conditions. It has been shown that, in all instances, the composition and properties of the iron-containing phases in the composites depend significantly on both synthesis and heat treatment conditions.

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Solid Platinum Superoxo Hydroxo Complex

EPR Spectra Of Green Solid Platinum Superoxo Hydroxo Species

Solid Platinum Superoxo Hydroxo Complex. Pankratov D.A., Komozin P.N., Kiselev Yu.M. //Russian Journal of Inorganic Chemistry. 2000. V. 45. № 10. P. 1555-1559

Solid samples isolated from solutions of a platinum superoxo hydroxo complex are studied by EPR and X-ray powder diffraction techniques. The short-lived superoxo complex is found to form upon dissolution of the solid samples in concentrated acids. Magnetic resonance parameters of the platinum superoxo complexes in the solid state and in acidic solutions are determined. The structures of the inner coordination sphere of the found superoxo complexes are discussed.

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New Platinum Superoxo Complex

Evolution of the VIS-spectra of the pink solutions in time

New Platinum Superoxo Complex. Kiselev Yu.M., Pankratov D.A., Shundrin L.A., Kiseleva I.N. //Russian Journal of Inorganic Chemistry. 1996. V. 41. № 12. P. 1963-1966Search the full text below. Ищи полный текст ниже.

Products of oxidation of Pt(IV) hexahydroxo complexes with ozone in alkali media have been studied with physicochemical methods (electron spectroscopy, EPR, and cyclic voltammetry). The oxidation product is pink at alkali concentration in solution higher than 5 mol/l. The pink complex represents previously undescribed platinum superoxo complex with a bridging O2- group.

Our previous study concerned the possibility of preparing platinum compounds in unusually high oxidation states from alka1ine solutions under the action of ozone. In that study, we detected a blue platinum superoxo complex of binuclear structure with the O2- bridging group. The bridge structure of this complex was supported by ESR, and the complex was show to form only at rather low alkalinity. At higher alkali concentrations (cOH- > 5 mol/l), a similar reaction results in a pale pink complex containing oxidizer.

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