Abstract

The efficiency of the sorption of Eu(III) by various forms of Mg,Al- and Zn,Al-layered double hydroxides (LDH) from model and natural waters at various pH was estimated for concentrating this metal ions and its subsequent spectrophotometric determination. It was found that the almost complete extraction of Eu(III) is reached on the carbonate form of Mg,Al-LDH by a deposition mechanism because of the formation of poorly soluble compounds of this element (carbonate and hydroxide of Eu(III) at pH ≥ 6.2, which correlates with the calculated Eu(III) speciation in aqueous solution in the presence of carbonate ions. The distribution coefficients of Eu(III) are 1.4 × 10⁶ cm³/g (the pH of the initial solution is ≥7.0; the pH of the solution after the sorption is ≥ 6.87), which is indicative of a high efficiency of this sorbent with respect to this metal ion. For Mg,Al- and Zn,Al-LDH intercalated with organic complex-forming ligands—citrate and ethylenediaminetetraacetate ions, the dominant mechanism Eu(III) extraction from aqueous media is the complex formation. The distribution coefficients of Eu(III) on these sorbents are (0.26—22.71) × 10³ cm³/g. For concentrating Eu(III) and its spectrophotometric determination in natural waters, it was proposed to use the carbonate form of Mg,Al-LDH with its subsequent decomposition by a nitric acid solution after the sorption. It was shown that the major components of natural waters and the constituents of this sorption materials do not affect the correctness and accuracy of the determination of Eu(III) by this method with arsenazo III (at pH 2.6 ± 0.1). The linearity range of the calibration graph is 1–50 μg Eu(III) in 50 cm³ of the final solution cm³ (λ = 650 nm). The proposed method of concentrating and determining Eu(III) was tested on samples of model, tap, and surface waters (the sorbent weight is 0.100 g, and the water sample volume is 500 cm³).

中文翻译：

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Mg，Al层状双金属氢氧化物的碳酸盐形式，用于浓缩Eu（III）及其在天然水介质中的分析测定

摘要

估算了在各种pH值下，模型水和天然水中各种形式的Mg，Al和Zn，Al层状双层氢氧化物（LDH）吸附Eu（III）的效率，以浓缩该金属离子并进行分光光度法测定。已发现通过沉积机理以Mg，Al-LDH的碳酸盐形式几乎完全提取了Eu（III），这是因为该元素的难溶化合物（Eu（III）的碳酸盐和氢氧化物pH≥6.2，与存在碳酸根离子时水溶液中的Eu（III）形态有关，Eu（III）的分布系数为1.4×10 ⁶ cm ³/ g（初始溶液的pH≥7.0；吸附后溶液的pH≥6.87），这表明该吸附剂相对于该金属离子具有高效率。对于插入形成有机络合物的配体柠檬酸和乙二胺四乙酸根离子的Mg，Al-和Zn，Al-LDH，从水介质中萃取Eu（III）的主要机理是络合物的形成。Eu（III）在这些吸附剂上的分布系数为（0.26-22.71）×10 ³ cm ³/G。为了浓缩天然水中的Eu（III）及其分光光度法，建议使用碳酸盐形式的Mg，Al-LDH，然后在吸附后通过硝酸溶液将其分解。结果表明，天然水的主要成分和该吸附材料的成分不会影响使用砷偶氮Ⅲ（在pH 2.6±0.1）下用此方法测定Eu（III）的正确性和准确性。在最终溶液50 cm ³ cm ³（λ= 650 nm）中，校准图的线性范围是1–50μgEu（III ）。在模型水，自来水和地表水（吸附剂重量为0.100 g，水样品体积为500 cm ³）的样品上测试了所建议的浓缩和确定Eu（III）的方法。