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J Solution Chem. 2017;46(1):25-43. doi: 10.1007/s10953-016-0555-x. Epub 2016 Dec 17.

Complexation of Nickel Ions by Boric Acid or (Poly)borates.

Author information

1
EDF R&D - Department of Material and Mechanic of Component, EDF Lab Les Renardières, Avenue des Renardières - Ecuelles, 77818 Moret-Sur-Loing Cedex, France.
2
EDF R&D - Department of Material and Mechanic of Component, EDF Lab Les Renardières, Avenue des Renardières - Ecuelles, 77818 Moret-Sur-Loing Cedex, France ; PPSM, ENS Cachan, CNRS, Université Paris - Saclay, 94235 Cachan, France.
3
EDF R&D - Department of Material and Mechanic of Component, EDF Lab Les Renardières, Avenue des Renardières - Ecuelles, 77818 Moret-Sur-Loing Cedex, France ; EDF R&D, Department Economic and Technical Analysis of Energy Systems (EFESE) - Institut of Research and Development on Photovoltaic Energy (IRDEP), EDF Lab - Chatou, 6 quai Wattier, 78400 Chatou Cedex, France.
4
Géosciences Environnement Toulouse, CNRS, Observatoire Midi-Pyrénées, Université de Toulouse, 14 avenue Edouard Belin, 31400 Toulouse, France.

Abstract

An experiment based on electrochemical reactions and pH monitoring was performed in which nickel ions were gradually formed by oxidation of a nickel metal electrode in a solution of boric acid. Based on the experimental results and aqueous speciation modeling, the evolution of pH showed the existence of significant nickel-boron complexation. A triborate nickel complex was postulated at high boric acid concentrations when polyborates are present, and the equilibrium constants were determined at 25, 50 and 70 °C. The calculated enthalpy and entropy at 25 °C for the formation of the complex from boric acid and Ni2+ ions are respectively equal to (65.6 ± 3.1) kJ·mol-1 and (0.5 ± 11.1) J·K-1·mol-1. The results of this study suggest that complexation of nickel ions by borates can significantly enhance the solubility of nickel metal and nickel oxide depending on the concentration of boric acid and pH. First principles calculations were investigated and tend to show that the complex is thermodynamically stable and the nickel cation in solution should interact more strongly with the [Formula: see text] than with boric acid.

KEYWORDS:

Aqueous; Boric acid; Complexation; DFT; Equilibrium constant; First principles; Nickel

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