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.

Formation Of Iron(VI) In Ozonalysis Of Iron(III) In Alkaline Solution

Mossbauer spectrum of Fe(VI) frozen solution in 5M NaOH (77 K)Formation of iron(VI) in ozonalysis of iron(III) in alkaline solution. Perfiliev Y.D., Benko E.M., Pankratov D.A., Sharma V.K., Dedushenko S.K. //Inorganica Chimica Acta. 2007. V.360. №8. P.2789-2791.Search the full text below. Ищи полный текст ниже.

Here we report the formation of iron in hexavalent state, FeVIO42- in ozonalysis of iron(III) in alkaline medium. The formation of tetrahedral FeVIO42- ion is confirmed by UV–Visible and Mössbauer spectroscopic techniques. The value of isomer shift - δ, of the tetraoxyanion is consistent with known δ values for various salts of iron(VI) ion.

Iron is the most abundant transition element on Earth and commonly exists in compounds of its +2 and +3 oxidation states. Iron ions in these two oxidation states are generally used in biological electron transfer processes. Iron in higher oxidation states such as +4, +5, and +6 are involved in iron enzymes, organic synthesis, and Fenton chemistry. Examples include capability of Fe(IV) and Fe(V) at enzymatic sites to abstract H and/or to break C–C bond, participation of high-valent nonheme ironoxo species in biometric oxidations, and involvement of aqua oxoiron(IV) in environmental and catalytic chemistry.

EPR Spectroscopy Of Transformations Of Iridium(III) And Iridium(IV) Hydroxo Complexes In Alkaline Media

Schematics of transformation of iridium compounds in alkaline solutions (where the area of each block is proportional to the number of moles of a reagent involved in reaction)EPR spectroscopy of transformations of iridium(III) and iridium(IV) hydroxo complexes in alkaline media. Pankratov D.A., Komozin P.N., Kiselev Yu.M. //Russian Journal of Inorganic Chemistry. 2011. V.56. №11. P.1794-1799.Search the full text below. Ищи полный текст ниже.

Processes that occur in strong alkaline solutions of iridium(III) and iridium(IV) hydroxo complexes have been studied by EPR and electronic absorption spectroscopy. It has been demonstrated that dissolution of iridium compounds in alkaline solutions should be accompanied by a series of complicated transformations involving oxygen, which lead to the formation of several binuclear iridium(III, III), (III, IV), and (IV, IV) dioxygen complexes.

Most research into the chemistry of platinum metals has focused on their complexes. However, the chemistry of their hydroxo complexes is still one of the least studied fields. There are both objective (experimental complexity of operation in alkaline and strong alkaline media, tendency to polymerization of many hydroxo compounds, and others) and subjective reasons for this situation. In particular, it is believed that the chemistry of platinum metal hydroxo complexes is insufficiently diverse. Nevertheless, we previously showed the possibility of the existence of platinum(IV) hydroxo complexes as mono- and binuclear as mono- (superoxo-) and bi- (hydroxo- and superoxo-) bridging superoxo complexes of different composition forming under oxidative conditions in strong alkaline media.

Mössbauer Diagnostics of the Isomorphic Substitution of Iron for Aluminum in Triclinic Iron Vanadate

Dependence on the fraction of iron atoms in the i-th position in respective surrounding j on the degree of substituting x in AlxFe3 – xV3O12Mössbauer Diagnostics of the Isomorphic Substitution of Iron for Aluminum in Triclinic Iron Vanadate. Pankratov D.A., Yur’ev A.I. //Bulletin of the Russian Academy of Sciences. Physics. 2013. V.77. №6. P.759-764.Search the full text below. Ищи полный текст ниже.

Mössbauer spectroscopy and X-ray powder diffractometry (XRD) phase analysis are used to study mixed vanadates with the composition AlxFe3– xV3O12, where x is 0, 0.3, 1.0, 1.5, 2.0, 2.7 and 3.0. Mössbauer spectroscopy is used to study the distribution of trivalent cations over different crystallographic positions. It is shown that the distribution of aluminum atoms differs from those expected from statistic and thermodynamic models.

Materials based on iron and vanadium compounds, which include material doped by transition or nontransition metals, are widely used as catalysts and sensor materials. Apart from solid solutions, two individual compounds form in the iron(III) oxide–vanadium(V) oxide system in particular: Fe2V4O13 and FeVO4. In turn, iron ortovanadate FeVO4 crystallizes depending on the conditions in an orthorhombic or triclinic system. In addition to its use in catalysis, triclinic iron vanadate has recently attracted attention due to its interesting magnetic properties. The type of iron vanadate formed at normal pressures is a multiferroic, and antiferromagnetic ordering is observed in it at temperatures below 22 K.

Synthesis of nanohydroxyapatite in the presence of iron (III) ions

Room-temperature Mössbauer spectra of the 2-x samples, models for their description (left panels), and the corresponding quadrupole splitting probability distribution functions (right panels)Synthesis of nanohydroxyapatite in the presence of iron (III) ions. Severin A.V., Pankratov D.A. //Russian Journal of Inorganic Chemistry. 2016. V.61. №3. P.265-272.Search the full text below. Ищи полный текст ниже.

The effect of small amounts of iron (III) ions on the morphology, phase composition, and structure of the products of the hydroxyapatite (HAP) synthesis has been studied by electron microscopy, X-ray powder diffraction, and Mossbauer spectroscopy methods. It has been demonstrated that the introduction of dopant iron (III) ions into the reaction mixture at different stages of HAP formation makes it possible to control crystal growth, morphology, and phase composition. The iron ions are not incorporated into the HAP crystal structure; rather, they form their proper nanophase, as well as adsorption clusters on the HAP surface.


Мессбауэровская диагностика функциональных материалов

Мессбауэровская диагностика функциональных материалов