| 1. |
- Kravchenko, T A, et al.
(författare)
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Contribution of dimensional factor to the potential of copper-containing electron-ion exchangers
- 2006
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Ingår i: Russian journal of electrochemistry. - 1023-1935 .- 1608-3342. ; 42:3, s. 233-238
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Tidskriftsartikel (refereegranskat)abstract
- The average size of copper particles in copper-containing electron-ion exchangers is determined with the aid of microscopy and x-ray diffractornetry. The results are used to calculate the contribution made by a dimensional factor to the electrode potential. Compared to the potential of compact copper, the potential shift in the negative direction measured experimentally falls within the region of calculated values. The average size of copper particles remains practically unchanged after contact with a copper sulfate solution. testifying to stabilization of an ultradisperse state of copper particles by a polymer matrix.
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| 2. |
- Molochnikov, L. S., et al.
(författare)
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Coordination of Cu(II) and Ni(II) in polymers imprinted so as to optimize amine chelate formation
- 2003
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Ingår i: Polymer. - : Elsevier BV. - 0032-3861 .- 1873-2291. ; 44:17, s. 4805-4815
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Tidskriftsartikel (refereegranskat)abstract
- Molecular imprinting has become an established technique. However, little was done on direct investigation of the sorbents produced. In the present work, en ESR method was used for the investigation of the complex formation processes within the sorbents imprinted with copper(II) and nickel(II). The sorbents were synthesized from a mixture of linear low molecular weight polyethyleneimine oligomers. The composition, structure and distribution of complexes in the resin phase were investigated. The effects of the synthesis conditions, loading degree and water content were examined. The presence of certain copper complexes was found to be a convenient characteristic of the imprinting efficiency. The optimum synthesis conditions for obtaining sorbents imprinted with copper(II) or nickel(II) were identified. The imprinting results in the improvement of the stability of the complexes and the selectivity and working capacity of the sorbents. The imprinted samples are also characterized by a more even distribution of chelating sites. The synthesis conditions and loading by ions allow for the regulation of the ratio between individual complexes and magnetic associates in the resin phase. This is a critical point on the future use of the metal containing imprinted sorbents as catalysts.
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| 3. |
- Samoilov, A. M., et al.
(författare)
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Vapor formation and thermodynamic properties of the gallium-lead system melts
- 2011
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Ingår i: Russian journal of general chemistry. - 1070-3632 .- 1608-3350. ; 81:1, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- A vapor composition and thermodynamic properties of melts of the gallium-lead system were studied by high-temperature mass-spectrometry. It was shown on the basis of thermodynamic calculations that Ga1-x Pb (x) melts are characterized by an appreciable positive deviation from the ideal behavior in the temperature range 780-1170 K.
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| 4. |
- Biesuz, R., et al.
(författare)
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Estimation of deprotonation coefficients for chelating ion exchange resins. Comparison of different thermodynamic model
- 2001
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:20, s. 4721-4726
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Tidskriftsartikel (refereegranskat)abstract
- The deprotonation of quinolic resin P-127 and iminodiacetic resin Amberlite IRC-718 has been studied. The process of salt transfer into the resin phase is considered to be an important contributor to the deprotonation process. Estimation of the salt transfer was based on the principle of equal activity of the salt in both phases at equilibrium. Two assumptions were made: sorbed alkali metal ions are not associated with functional groups, while all hydrogen ions are associated with functional groups. The associated hydrogen ions and functional groups do not contribute to the internal ionic strength value. Two thermodynamic models, describing the deprotonation of ion-exchange resin, were used and compared: the Gibbs-Donnan-based model of Bukata and Marinsky and the model proposed by Erik Hogfeldt. Thermodynamic characteristics of the resins' deprotonation are obtained using two different thermodynamic approaches. Hogfeldt's three-parameter model provides a better agreement with experimental data. The fitting of the data to Marinsky's method can be improved by taking into account the influence of the resins' macroporosity; however, this requires an additional empirical parameter to describe the resin.
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| 5. |
- Molochnikov, L S, et al.
(författare)
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Direct measurement of H+ activity inside cross-linked functional polymers using nitroxide spin probes
- 2004
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:4, s. 1302-1313
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Tidskriftsartikel (refereegranskat)abstract
- The lack of a direct method for measuring activity inside ion-exchamye resins was the main obstacle for strict thermodynamic investigations of such objects during the past decades. This paper proposes a method for the activity determination. The method is based on exploring the ESR response of stable nitroxide radicals introduced as probes into the resin phase. This method allows for the measurement of the hydrogen ion activity inside cross-linked polyelectrolytes. In addition to the method verification, the paper reports its application to the determination of ionization constants of functional groups and to the investigation of the hydrolysis and sorption of copper on different types of sorbents (weak cation and anion-exchange resins, functionalized and nonfunctionalized polymeric films). The applicability of known thermodynamic approaches developed for the investigation of micelles and biomembranes with nitroxide radicals is discussed. The paper also includes a critical analysis of the potentiometric method conventionally used for the investigation of ion-exchange equilibria.
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| 6. |
- Salazar-Alvarez, G., et al.
(författare)
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Novel flow injection synthesis of iron oxide nanoparticles with narrow size distribution
- 2006
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 61:14, s. 4625-4633
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Tidskriftsartikel (refereegranskat)abstract
- A novel synthesis method based on a flow injection technique was developed and the synthesis of magnetite nanoparticles was performed to demonstrate the concept. The technique consisted of continuous or segmented mixing of reagents under laminar flow regime in a capillary reactor. Different schemes of the flow injection synthesis were evaluated and the continuous mode was found to be more advantageous for the synthesis of the iron oxide particles. The material was characterised by X-ray diffraction, thermal analysis, electron microscopy, and magnetic susceptometry. The obtained magnetite nanoparticles had a narrow size distribution in the range 2-7 nm. The influence of chemical parameters and conditions on properties of the material was investigated.
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| 7. |
- Samoilov, A. M., et al.
(författare)
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Vaporization and thermodynamic properties of indium-lead melts
- 2008
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Ingår i: Russian journal of general chemistry. - 1070-3632 .- 1608-3350. ; 78:1, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Vapor composition and thermodynamic properties of melts of the In-Pb system were studied by high-temperature mass spectrometry. In the temperature range 780-1170 K, the In1-xPbx melts feature an appreciable positive deviation from the ideal behavior.
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| 8. |
- Horvath, I. S., et al.
(författare)
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Selection of anion exchangers for detoxification of dilute-acid hydrolysates from spruce
- 2004
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Ingår i: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 113, s. 525-538
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Tidskriftsartikel (refereegranskat)abstract
- Six anion-exchange resins with different properties were compared with respect to detoxification of a dilute-acid hydrolysate of spruce prior to ethanolic fermentation with Saccharomyces cerevisiae. The six resins encompassed strong and weak functional groups as well as styrene-, phenol-, and acrylic-based matrices. In an analytical experimental series, fractions from columns packed with the different resins were analyzed regarding pH, glucose, furfural, hydroxymethylfurfural, phenolic compounds, levulinic acid, acetic acid, formic acid, and sulfate. An initial adsorption of glucose occurred in the strong alkaline environment and led to glucose accumulation at a later stage. Acetic and levulinic acid passed through the column before formic acid, whereas sulfate had the strongest affinity. In a preparative experimental series, one fraction from each of six columns packed with the different resins was collected for assay of the fermentability and analysis of glucose, mannose, and fermentation inhibitors. The fractions collected from strong anion-exchange resins with styrene-based matrices displayed the best fermentability: a sevenfold enhancement of ethanol productivity compared with untreated hydrolysate. Fractions from a strong anion exchanger with acrylic-based matrix and a weak exchanger with phenol-based resin displayed an intermediate improvement in fermentability, a four- to fivefold increase in ethanol productivity. The fractions from two weak exchangers with styrene- and acrylic-based matrices displayed a twofold increase in ethanol productivity. Phenolic compounds were more efficiently removed by resins with styrene- and phenol-based matrices than by resins with acrylic-based matrices.
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| 9. |
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| 10. |
- Zagorodni, Andrei A., et al.
(författare)
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Bar-shaped nanoparticles of iron(II) hydroxide
- 2008
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Ingår i: Journal of nanoparticle research. - : Springer Science and Business Media LLC. - 1388-0764 .- 1572-896X. ; 10:2, s. 377-381
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Tidskriftsartikel (refereegranskat)abstract
- Formation of elongated nanoparticles was observed when FE3O4 was precipitated from solutions containing excess of Fe2+. The average diameter of the particles was 23 nm; the length to diameter ratio was up to 14. This shape was an unexpected phenomenon because bar- or needle-like nanoparticles have been earlier reported only for Fe(III)-based materials. Chemical analysis revealed Fe(OH)(2) nature of the obtained particles. In addition, this conclusion was verified with a new simple method for quantitative evaluation of the particle morphology. Application of this method to the mixed Fe(OH)(2/)Fe3O4 samples allowed to distinguish between the two different compounds and to attribute different morphologies to Fe(OH)(2) or Fe3O4. Results indicate that bars are frequent shapes of nano-sized iron oxides/hydroxides.
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