Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/97076
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Type: Journal article
Title: Thermodynamic modeling of poorly complexing metals in concentrated electrolyte solutions: an X-ray absorption and UV-Vis spectroscopic study of Ni(II) in the NiCl₂-MgCl₂-H₂O system
Other Titles: Thermodynamic modeling of poorly complexing metals in concentrated electrolyte solutions: an X-ray absorption and UV-Vis spectroscopic study of Ni(II) in the NiCl(2)-MgCl(2)-H(2)O system
Author: Zhang, N.
Brugger, J.
Etschmann, B.
Ngothai, Y.
Zeng, D.
Citation: PLoS One, 2015; 10(4):e0119805-1-e0119805-23
Publisher: Public Library of Science
Issue Date: 2015
ISSN: 1932-6203
1932-6203
Statement of
Responsibility: 
Ning Zhang, Joël Brugger, Barbara Etschmann, Yung Ngothai, Dewen Zeng
Abstract: Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg(-1) NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg(-1) NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system.
Keywords: Magnesium Chloride; Electrolytes; Ions; Nickel; Water; Solutions; Spectrophotometry, Ultraviolet; Thermodynamics; Models, Chemical; Coordination Complexes; X-Ray Absorption Spectroscopy
Rights: © 2015 Zhang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
RMID: 0030029785
DOI: 10.1371/journal.pone.0119805
Appears in Collections:Earth and Environmental Sciences publications

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