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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Interaction of Np(v) with borate in alkaline, dilute-to-concentrated, NaCl and MgCl2 solutions
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Interaction of Np(v) with borate in alkaline, dilute-to-concentrated, NaCl and MgCl2 solutions

机译：NP（V）与碱性，稀富浓，NaCl和MgCl2溶液相互作用

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The interaction of Np(v) with borate was investigated in 0.1-5.0 M NaCl and 0.25-4.5 M MgCl2 solutions with 7.2 <= pH(m) <= 10.0 (pH(m) = -log[H+]) and 0.004 M <= [B](tot) <= 0.16 M. Experiments were performed under an Ar-atmosphere at T = (22 +/- 2) degrees C using a combination of under- and oversaturation solubility experiments, NIR spectroscopy, and extensive solid phase characterization. A bathochromic shift (approximate to 5 nm) in the Np(v) band at lambda = 980 nm indicates the formation of weak Np(v)-borate complexes under mildly alkaline pH(m)-conditions. The identification of an isosbestic point supports the formation of a single Np(v)-borate species in dilute MgCl2 systems, whereas a more complex aqueous speciation (eventually involving the formation of several Np(v)-borate species) is observed in concentrated MgCl2 solutions. The solubility of freshly prepared NpO2OH(am) remained largely unaltered in NaCl and MgCl2 solutions with [B](tot) = 0.04 M within the timeframe of this study (t <= 300 days). At [B](tot) = 0.16 M, a kinetically hindered but very significant drop in the solubility of Np(v) (3-4 log(10)-units, compared to borate-free systems) was observed in NaCl and dilute MgCl2 solutions with pH(m) <= 9. The drop in the solubility was accompanied by a clear change in the colour of the solid phase (from green to white-greyish). XRD and TEM analyses showed that the amorphous NpO2OH(am) "starting material" transformed into crystalline solid phases with similar XRD patterns in NaCl and MgCl2 systems. XPS, SEM-EDS and EXAFS further indicated that borate and Na/Mg participate stoichiometrically in the formation of such solid phases. Additional undersaturation solubility experiments using the newly formed Na-Np(v)-borate(cr) and Mg-Np(v)-borate(cr) compounds further confirmed the low solubility ([Np(v)](aq) approximate to 10(-6)-10(-7) M) of such solid phases in mildly alkaline pH(m)-conditions. The formation of these solid phases represents a previously unreported retention mechanism for the highly mobile Np(v) under boundary conditions (pH(m), [B](tot), ionic strength) of relevance to certain repository concepts for nuclear waste disposal.
机译：在0.1-5.0m NaCl和0.25-4.5M MgCl 2溶液中研究了NP（V）与硼酸盐的相互作用，其中7.2 <= pH（m）<= 10.0（pH（m）= -log [H +]）和0.004米<= [B]（Tot）<= 0.16米。使用诸如过饱和溶解度实验，NIR光谱和广泛的固体的组合在T =（22 +/- 2）℃下的Ar-气氛下进行实验相表征。在Lambda = 980nm处的NP（v）带中的碱基转移（近似为5nm）表明在轻度碱性pH（m）-concitions下形成弱NP（v） - 硼酸酯络合物。 Isosbestic点的鉴定支持在稀MgCl2系统中形成单个NP（V） - 硼酸酯物种，而在浓缩的MgCl 2中观察到更复杂的含水物质（最终涉及形成几种NP（V） - 硼酸酯物种）解决方案。新鲜制备的NPO 2 OH（AM）的溶解度在NaCl和MgCl 2溶液中仍然在很大程度上没有[B]（Tot）= 0.04M在该研究的时间范围内（T <= 300天）。在[b]（Tot）=0.16μm，在NaCl中观察到NP（v）的溶解度（3-4 v）（3-4对数（10） - 与无硼系统相比）的动力学但非常显着下降），并稀释MgCl2具有pH（m）的溶液<= 9。溶解度的下降伴随着固相的颜色的澄清变化（从绿色到白色灰色）。 XRD和TEM分析表明，具有在NaCl和MgCl2系统中具有相似XRD图案的结晶固相的无定形NPO2OH（AM）“起始材料”。进一步表明硼酸盐和Na / mg在形成这种固相的形成中，硼酸硼和Na / mg参与。使用新形成的Na-NP（V） - 硼酸酯（Cr）和Mg-NP（V） - 硼酸酯（Cr）化合物的额外的低溶解度实验进一步证实了低溶解度（[NP（V）]（AQ）近似为10 （-6）-10（-7）m）在轻度碱性pH（m）中的这种固相。这些固相的形成是在与核废物处理的某些储存概念相关的边界条件下（pH（m），[b]（tot），离子强度）下的高度移动NP（v）的先前未报告的保留机制。

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