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Complexation of Nickel Ions by Boric Acid or (Poly)borates
Anais Graff1, Etienne Barrez2, Philippe Baranek3
1EDF R&D - Department of Material and Mechanic of Component, EDF Lab Les Renardières, Avenue des Renardières - Ecuelles, 77818 Moret-Sur-Loing Cedex, France.
Journal of Solution Chemistry
|February 7, 2017
Summary
Nickel-boron complexation significantly increases nickel solubility in boric acid solutions. This study quantifies complex formation and its thermodynamic stability, impacting nickel metal and oxide dissolution.
Area of Science:
- Electrochemistry
- Aqueous Geochemistry
- Materials Science
Background:
- Nickel ions are prevalent in various industrial and environmental systems.
- Understanding nickel speciation is crucial for predicting its behavior and fate.
- Boric acid is a common component in solutions, potentially interacting with metal ions.
Purpose of the Study:
- To investigate nickel-boron complexation in boric acid solutions.
- To determine the thermodynamic properties of nickel-borate complexes.
- To assess the impact of complexation on nickel solubility.
Main Methods:
- Electrochemical oxidation of nickel metal electrode.
- In-situ pH monitoring.
- Aqueous speciation modeling.
- Thermodynamic equilibrium constant determination.
- First principles calculations.
Main Results:
- Experimental evidence and modeling confirmed significant nickel-boron complexation.
- A triborate nickel complex was identified at high boric acid concentrations.
- Equilibrium constants were determined across a temperature range (25-70 °C).
- Thermodynamic data (enthalpy and entropy) for complex formation were calculated.
- First principles calculations supported the stability of the nickel-borate complex.
Conclusions:
- Nickel-boron complexation enhances the solubility of nickel metal and nickel oxide.
- The extent of solubility enhancement is dependent on boric acid concentration and pH.
- The nickel cation exhibits stronger interactions with borate species than with boric acid itself.
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