Desorption of radioactive cesium by seawater from the suspended particles in river water
Desorption of radioactive cesium by seawater from the suspended particles in river water
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海水对河水中悬浮颗粒放射性铯的解吸
DOI：
10.1016/j.chemosphere.2017.07.078
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发表时间：
2017
期刊：
影响因子：
8.8
通讯作者：
N. Sato
中科院分区：
文献类型：
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作者：
M. Onodera;A. Kirishima;S. Nagao;K. Takamiya;T. Ohtsuki;D. Akiyama;N. Sato
2011年，福岛第一核电站的事故将放射性铯扩散到整个环境中，污染了土地、河流和海洋。含有粘土矿物的悬浮颗粒是放射性铯从河流到海洋的运输介质，因为铯在粘土矿物层之间被强烈吸附，形成内部球体复合物。本文研究了河流中悬浮粘土颗粒对放射性铯的吸附和解吸行为。用137cs示踪剂对两种悬浮颗粒进行了放射性铯的吸附和解吸实验。在解吸实验前进行的铯吸附处理中，使用总铯浓度（[133+137Cs+]total）为1.3 nM（10−9mol/L）的模拟河水。解吸实验主要在固液比为0.17 g/L时进行。解吸剂为福岛第一核电站以北10 km处采集的天然海水、人工海水、NaCl、KCl、NH4Cl、133cscl溶液和超纯水。研究了悬浮粒子中预载铯浓度对解吸行为的影响。通过载铯量约为1000 ng/g的悬浮粒子对铯的解吸实验，确定了各解吸剂对铯的解吸比顺序为：1 M NaCl (80%) > 470 mM NaCl (65%) > 1 M KCl(30%)≈海水（天然海水和岱古人工海水）> 1 M NH4Cl (20%) > 1 M133CsCl（15%）比超纯水（2%）。此外，我们还得到了一个有趣的结果：尽管Na+浓度相同，但在470 mM NaCl溶液中的解吸率远高于在海水中的解吸率。这些结果表明，铯的解吸机制不是简单的离子交换反应，而是与悬浮颗粒中粘土矿物的结构变化密切相关。水合Na+离子扩大了黏土矿物的层间距离，使铯易于解吸；相反，脱水的K+离子减少了层间距离，抑制了铯的脱附。综上所述，悬浮粒子中铯的解吸受钠离子和钾离子的存在以及悬浮粒子中预载铯浓度的控制。
In 2011, the accident at the Fukushima-Daiichi nuclear power plant dispersed radioactive cesium throughout the environment, contaminating the land, rivers, and sea. Suspended particles containing clay minerals are the transportation medium for radioactive cesium from rivers to the ocean because cesium is strongly adsorbed between the layers of clay minerals, forming inner sphere complexes. In this study, the adsorption and desorption behaviors of radioactive cesium from suspended clay particles in river water have been investigated. The radioactive cesium adsorption and desorption experiments were performed with two kinds of suspended particulate using a batch method with137Cs tracers. In the cesium adsorption treatment performed before the desorption experiments, simulated river water having a total cesium concentration ([133+137Cs+]total) of 1.3 nM (10−9mol/L) was used. The desorption experiments were mainly conducted at a solid-to-liquid ratio of 0.17 g/L. The desorption agents were natural seawater collected at 10 km north of the Fukushima-Daiichi nuclear power plant, artificial seawater, solutions of NaCl, KCl, NH4Cl, and133CsCl, and ultrapure water. The desorption behavior, which depends on the preloaded cesium concentration in the suspended particles, was also investigated. Based on the cesium desorption experiments using suspended particles, which contained about 1000 ng/g loaded cesium, the order of cesium desorption ratios for each desorption agent was determined as 1 M NaCl (80%) > 470 mM NaCl (65%) > 1 M KCl (30%) ≈ seawater (natural seawater and Daigo artificial seawater) > 1 M NH4Cl (20%) > 1 M133CsCl (15%) ≫ ultrapure water (2%). Moreover, an interesting result was obtained: The desorption ratio in the 470 mM NaCl solution was much higher than that in seawater, even though the Na+concentrations were identical. These results indicate that the cesium desorption mechanism is not a simple ion exchange reaction but is strongly related to structural changes in the clay minerals in the suspended particles. Hydrated Na+ions expand the interlayer distance of the clay minerals, resulting in the facile desorption of cesium; in contrast, dehydrated K+ions reduce the interlayer distance and inhibit the desorption of cesium. In conclusion, the desorption of cesium from the suspended particles is controlled by the presence of sodium and potassium ions and the preloaded cesium concentration in the suspended particles.