Abstract

We studied the adsorption extraction of Eu(III) from aqueous media by Zn,Al- and Mg,Al-layered double hydroxides (LDHs), intercalated by citrate ions, and their composites with magnetic properties. Cations typical of natural waters (Na⁺, K⁺, Ca²⁺, Mg²⁺) do not affect the efficiency of water purification from Eu(III), and humic acids even increase it when using composite materials. The following conditions for the extraction of Eu(III) were determined: pH of the aqueous medium, adsorption kinetics, adsorbent dose, and the effect of organic and inorganic macrocomponents of aqueous media. The adsorption equilibrium is achieved for the studied citrate forms of LDH and their magnetic composites after 1 h of contact of the aqueous solution with the solid phase of the adsorbents. Based on the parameters of kinetic models and linear correlation coefficients, we demonstrated that Eu(III) adsorption with these LDH forms is most reliably described by a pseudosecond order model in the entire range of adsorption durations, in contrast to the pseudofirst-order model. This indicates the prevailing mechanism for the extraction of Eu(III) due to chemisorption, and the equilibrium adsorption values calculated theoretically from the pseudosecond-order model are in good agreement with the experimental ones. The adsorption isotherms of Eu(III) on the citrate forms of Zn,Al- and Mg,Al-LDHs and their magnetic composites were processed using the Freundlich and Langmuir equations; these adsorption models satisfactorily describe the experimental data (correlation coefficients ≥0.99). The forms of the presence of Eu(III) in aqueous solutions are calculated at different pH values in the presence of citrate ions and natural organic ligands (fulvic acids). We propose the mechanism of removal of Eu(III) from aqueous media. The results give grounds to recommend the studied materials as effective adsorbents of radionuclide-complexing agents for the purification of contaminated surface water and liquid radioactive waste using adsorption technology with magnetic separation of sludge.

中文翻译：

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柠檬酸根离子嵌入的锌，铝和镁，铝层状双氢氧化物水溶液中对Eu（III）的吸附

摘要

我们研究了锌，铝和镁，铝层的双氢氧化物（LDHs）从柠檬酸根离子插层到水介质中的Eu（III）的吸附萃取及其具有磁性的复合材料。天然水的典型阳离子（Na ⁺，K ⁺，Ca 2 ⁺，Mg ²⁺）不会影响从Eu（III）净化水的效率，而腐殖酸甚至在使用复合材料时也会提高腐殖酸的效率。确定了萃取Eu（III）的以下条件：水性介质的pH，吸附动力学，吸附剂剂量以及水性介质中有机和无机大分子成分的影响。在水溶液与吸附剂固相接触1小时后，LDH柠檬酸盐及其磁性复合材料的柠檬酸盐形式达到了吸附平衡。基于动力学模型的参数和线性相关系数，我们证明，与伪一阶模型相比，用LDH形式的Eu（III）吸附在整个吸附持续时间范围内最可靠地由伪二阶模型描述。这表明了由于化学吸附作用而提取Eu（III）的主要机理，并且根据拟二级模型理论计算出的平衡吸附值与实验值基本吻合。用Freundlich和Langmuir方程处理了Eu（III）在柠檬酸盐形式的Zn，Al和Mg，Al-LDHs及其磁性复合材料上的吸附等温线；这些吸附模型令人满意地描述了实验数据（相关系数≥0.99）。在柠檬酸根离子和天然有机配体（富里酸）存在下，在不同的pH值下计算出Eu（III）在水溶液中的存在形式。我们提出了从水性介质中去除Eu（III）的机理。