A conceptual model to predict uranium removal from aqueous solutions in water-rock systems associated with low- and intermediate-level radioactive waste disposal
A conceptual model to predict uranium removal from aqueous solutions in water-rock systems associated with low- and intermediate-level radioactive waste disposal
复制标题
预测与中低水平放射性废物处置相关的水岩系统中水溶液中铀去除的概念模型
DOI：
10.1039/c6ra26773d
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发表时间：
2017
期刊：
影响因子：
3.9
通讯作者：
Kenney J
中科院分区：
文献类型：
--
作者：
Kenney J
全球贮存的放射性废物都安置在表面贮存处，在那里锕系元素容易受到环境释放的影响。当务之急是建立废物处理设施，以安全地容纳这些废物。然而，要做到这一点，我们必须确保工程和自然屏障足以防止埋藏的物质迁移到地表。从储存库（ILW和LLW）迁移的解决方案将具有广泛的化学成分和概念模型，这些模型将限制关键的矿泉水相互作用与现实岩性，这是迫切需要的。为此，我们进行了实验，研究在pH为2 - 12的范围内，不同浓度的U (10 ppb、0.1 ppm、1 ppm和10 ppm)，以及在0.1 M NaCl电解质中添加和不添加碳酸氢盐（2 mM），通过矿物表面与石英、砂岩和火山岩的相互作用，从溶液中去除U。我们观察到，溶液中的铀浓度对溶液中铀的去除程度的影响不大，作为pH值或石英和砂岩中碳酸氢盐浓度的函数，但对于火山岩来说很重要，在pH 4至8之间，随着铀浓度的增加，吸附对铀的去除程度降低。当向溶液中添加碳酸氢盐时，石英、砂岩和火山岩的地质材料在固定铀的能力方面表现出类似的能力，在pH为4-8时，吸附包膜会增加铀的去除，可能是通过沉淀，在高pH下。当不添加碳酸氢盐时，从溶液中去除铀的作用更受地质材料的控制。在pH 6-10时加入碳酸氢盐降低了吸附。然而，在pH值为10 - 12时，加入10ppm U的碳酸氢盐可以使U在岩石表面沉淀，使碳酸氢盐成为固定因素。因此，我们的概念模型表明，在低(6)和高（11）pH下，U从放射性废物样溶液中以双峰分布固定。
Global stores of radioactive waste are housed in surface stores where actinides are susceptible to environmental release. It is imperative that waste disposal facilities are built to safely contain this waste. However, to do this we must ensure that the engineered and natural barriers are sufficient to prevent the buried materials from migrating through to the surface. Solutions migrating from repositories (ILW and LLW) will have a wide range of chemical compositions and conceptual models constraining the key mineral-water interactions with realistic lithologies are urgently needed. To this end, we conducted experiments to study U removal from solution via mineral-surface interactions with quartz, sandstone, and volcanic rock over a pH range of 2–12, with varying concentrations of U (10 ppb, 0.1 ppm, 1 ppm, and 10 ppm) and with and without bicarbonate added (2 mM) with 0.1 M NaCl electrolyte. We observed that the U concentration in solution had little effect on the extent of U removal from solution as a function of pH or bicarbonate concentration with quartz and sandstone but was important for volcanic rocks, where removal of U, due to adsorption, decreased with increasing U concentration between pH 4 and 8. When bicarbonate was added to solution then the quartz, sandstone, and volcanic rock geomaterials acted similarly in their abilities to immobilize uranium, with an adsorption envelope from pH 4–8 followed by an increase in U removal, likely via precipitation, at high pH. When bicarbonate was not added, the removal of U from solution was more controlled by the geomaterial. Bicarbonate addition at pH 6–10 lowered adsorption. However, the addition of bicarbonate in experiments with 10 ppm U at pH 10–12 allowed for precipitation of U at the rock surface, making bicarbonate an immobilizing factor. Therefore, our conceptual model shows that U is immobilised from radioactive waste-like solutions in a bimodal distribution, both at low (6) and high (11) pH.