首页> 外文OA文献 >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
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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

机译:浓缩电解质溶液中络合性差的金属的热力学模拟:NiCl(2)-mgCl(2)-H(2)O体系中Ni(II)的X射线吸收和紫外 - 可见光谱研究

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摘要

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.
机译:含水Ni(II)-氯化物络合物的结构和形态的知识对于理解湿法冶金提取中的Ni行为很重要。在环境条件下,通过Ni K边缘X射线吸收(XAS)和UV-Vis光谱研究了浓度对NiCl2和NiCl2-MgCl2水溶液中Ni(II)的第一壳结构的影响。两种技术都表明没有大的结构变化(例如,从八面体转变为类似四面体的构型)。两种方法均证实,在整个NiCl2浓度范围内,Ni(II)铝离子(在RNi-O = 2.07(2)Å处具有六个配位水分子)是主要物质。但是,XANES,EXAFS和UV-Vis数据显示出在高盐度(> 2 mol∙kg(-1)NiCl2)下的细微变化,这与少量NiCl +络合物的形成(高达0.44(23)Cl在纯NiCl2溶液中在5.05 mol∙kg(-1)NiCl2中的Ni-Cl距离为2.35(2)Å。在NiCl2-MgCl2-H2O溶液中高Cl:Ni比的情况下,也存在少量的[NiCl2] 0。我们开发了基于形态的混合溶剂电解质(MSE)模型来描述NiCl2-MgCl2-H2O溶液中的活性-成分关系,并同时预测与XAS和UV-Vis数据一致的Ni(II)形态。并利用现有文献数据直至溶解度极限,解决了关于氯化物络合在该系统中的作用的长期不确定性。

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