2017-Sustainable Industrial Processing Summit
SIPS 2017 Volume 3. Gaune-Escard Intl. Symp. / Molten Salt and Ionic Liquid
| Editors: | Kongoli F, Fehrmann R, Gadzuric S, Gong W, Seddon KR, Malyshev V, Iwata S |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2017 |
| Pages: | 151 pages |
| ISBN: | 978-1-987820-65-2 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Study of the Influence Alkaline Earth Metal Cations on the Electrochemical Behavior of the Redox Couple Nb(V)/Nb(IV) in Alkali Halide Melt
Sergey Kuznetsov1; Darja Vetrova1;1INSTITUTE OF CHEMISTRY, KOLA SCIENCE CENTRE RAS, Apatity, Russian Federation;
Type of Paper: Regular
Id Paper: 84
Topic: 13
Abstract:
The aim of the present investigation was the study of charge transfer kinetics for the redox couple Nb(V)/Nb(IV) in the NaCl-KCl (equimolar mixture)-NaF(10 wt.%)-K2NbF7 melt and the estimation of the alkaline earth metal cations influence on the standard rate constants of charge transfer (ks) for this redox couple.
The redox process Nb(V) + e- <-> Nb(IV) in the (NaCl-KCl)eq.-NaF (10 wt %)-K2NbF7 melt was studied by cyclic voltammetry. The standard rate constants of charge transfer for the redox couple Nb(V)/Nb(IV) were calculated based on the Nicholson’s equation.
Influence of strongly polarizing cations of Mg2+, Ca2+, Sr2+ and Ba2+ on the standard rate constants of charge transfer for the redox couple Nb(V)/Nb(IV) was studied. It was found that addition of alkaline earth metal cations to the initial alkali chloride-fluoride melt resulted in increasing of ks up to the certain mole ratio of Me2+/Nb(V), which was inversely proportional to the ionic potential of cations. The increase of ks is connected with the substitution of Na+ and K+ cations by strongly polarizing cations in the second coordination sphere of niobium complexes that led to increasing of the bond distance between Nb and F ligands and decreasing of niobium fluoride complexes strength.
It was determined the linear dependence of ks on ionic potential of alkaline earth metal cations and the maximum value was obtained for complexes with outer sphere cation of magnesium.
Acknowledgments
The work was financially supported by Russian Foundation for Basic Research (15-03-02290_a).