Insight into the adsorption of europium(III) on muscovite and phlogopite: Effects of pH, electrolytes, humic substances and mica structures
Insight into the adsorption of europium(III) on muscovite and phlogopite: Effects of pH, electrolytes, humic substances and mica structures
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深入了解铕 (III) 在白云母和金云母上的吸附：pH、电解质、腐殖质和云母结构的影响
DOI：
10.1016/j.chemosphere.2021.131087
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发表时间：
2021
期刊：
影响因子：
8.8
通讯作者：
Mingliang Kang
中科院分区：
文献类型：
--
作者：
Hanyu Wu;Jie Chen;Zengbo Su;Bin Ma;Yizhe Ji;Shuhan Lin;Dingfang Xu;Mingliang Kang
铕（III），即，Eu（III）在化学上类似于三价镧系元素（Ln）和锕系元素（An）。了解Eu（III）在云母类矿物上的吸附行为对放射性污染的安全评价至关重要。然而，云母矿物结构的复杂性使得在Eu（III）迁移的研究中很难得出一致的结论。在这项工作中，我们对比研究了Eu（III）的吸附在双八面体白云母和三八面体金云母的pH值，离子强度，背景电解质，相互作用序列，和富里酸（FA）的功能。批处理实验表明，Eu（III）吸附在云母是强烈依赖于pH值，但相当独立的离子强度，这是由Na+。在Na+和Ca ~（2+）电解质条件下，白云母和金云母上均存在平面位，而金云母上只存在层间位（K+和Cs+不存在）。金云母的层间膨胀，如在~6° 2-θ处新出现的衍射峰所示，沿着Eu（III）的吸附，这也被透射电子显微镜证实。此外，Eu（III）的初始浓度、Eu（III）与Cs+的浓度比以及Eu（III）-电解质-FA的反应顺序均影响Eu（III）的吸附行为，并影响金云母的结构变化。连续萃取结果表明，Eu（III）主要以离子交换态吸附，FA的加入可增加Eu（III）的配位态比例。目前提出的Eu（III）吸附机理可以为在分子尺度上预测Ln/An（III）在富云母固液界面的迁移提供新的思路。
Europium(III), i.e., Eu(III), is chemically analogous to the trivalent lanthanides (Ln) and actinides (An). A good understanding of the adsorption behaviour of Eu(III) on mica group minerals is critical to the safety evaluation of the radioactive contamination. Nevertheless, the structural complexity of micaceous minerals makes it difficult to draw a consistent conclusion in the study of Eu(III) migration. In this work, we contrastively studied Eu(III) adsorption on dioctahedral muscovite and trioctahedral phlogopite as functions of pH, ionic strength, background electrolytes, interaction sequence, and fulvic acid (FA). Batch experiments showed that Eu(III) adsorption on both micas was strongly dependent on pH but quite independent on ionic strength that is determined by Na+. Planar sites are available on both muscovite and phlogopite while interlayer sites only on phlogopite under Na+and Ca2+electrolytes (not for K+and Cs+). An interlayer expansion of phlogopite, as indicated by a newly appeared diffraction peak at ~6° 2-theta, occurred along with Eu(III) adsorption, which was also confirmed by transmission electron microscopy. Furthermore, the initial Eu(III) concentrations, the concentration ratios between Eu(III) and Cs+, and the reaction sequences of Eu(III)-electrolytes-FA affected both the adsorption behaviour of Eu(III) and reversely the structural alteration of phlogopite. The sequential extraction showed that the adsorbed Eu(III) was mainly in the ion-exchangeable form while the addition of FA could increase the portion of coordinative species. The currently proposed Eu(III) adsorption mechanism can shed new light on predicting the migration of Ln/An(III) at the mica-rich solid-liquid interface on a molecular scale.