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 SM ISO690:2012ROZANTSEV, G., IGNATYEVA, V.. Study of LnW10O36 9- (Ln=Nd) ions state in aqueous solutions in alkali and acid media. In: Physical Methods in Coordination and Supramolecular Chemistry, 27 septembrie - 1 octombrie 2006, Chişinău. Chisinau, Republic of Moldova: 2006, XVII, p. 172. ISBN 978-9975-62-066-6. |
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| Physical Methods in Coordination and Supramolecular Chemistry XVII, 2006 |
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Conferința "The XV-th International Conference Physical Methods in Coordination and Supramolecular Chemistry : The XVII-th Reading in memory of Acad. A.Ablov" Chişinău, Moldova, 27 septembrie - 1 octombrie 2006 | ||||||
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Great posibilities for heteropoly compound use (organic catalysis, electronics, analytical procedures, medicine, etc.) arouse reseach interest to study the heteropoly ions state in aqueous solutions and to elaborate the optimal conditions of its synthesis in the solid state. Study of the equilibrium processes that take place in aqueous solution of the decatungstoneodymate-ions was done using the pH-titration in analyzable systems with different concentrations of the complex anion: 10-2; 10-3; 10-4 mol/l, in the range of ionic strengths: μ=0.1÷1.2, that were produced by the electrolyte solutions NaNO3, NaCl, Na2SO4 adding.. As a result the experimental dependence pH versus Z was obtained in alkali (ZOH-=-5÷0) and acid (ZH+=0÷5) ranges. These data were processed by the mathematical modelling method. Theoretically fitted model that describes ions state in acid pH range involved stepwise formation of the protonated ions by the following reaction: NdW10O36 9- + H+ ↔ HxNdW10O36 (9-x)- (x=1-5) In alkali media as pH increases the destruction of the decatungstoneodymate with NdW5O18 3formation was occurred. On reaching boundary ZOH-=-5 a heterogeneous system formation was observed that can be explained by complete destruction of all heteropoly compounds to Nd3+ and WO4 2- ions. Following the mathematical modelling of the equilibrium, concentration values for the complex ion were calculated and diagrams of the anionic species concentration versus ZH+/OH- were plotted. Pitzer’s method was used for the treatment of calculated set of logarithmic concentrational constants and were obtained logarithmic thermodynamic constants (lgKT) for the protonation process of the decatungstoneodymate-ions: HNdW10O36 8- H2NdW10O36 7- H3NdW10O36 6- H4NdW10O36 5- H5NdW10O36 4lgKT 7.58 14.39 19.99 23.77 28.96 Validity of the suggested model was confirmed by solid salt synthesis of the investigated complex ions from aqueous solutions in maximum substance content ranges. Structures and compositions of synthesized compounds were determined using chemical analysis and IR-spectroscopy. |
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