物理化学学报 >> 2017, Vol. 33 >> Issue (10): 2013-2021.doi: 10.3866/PKU.WHXB201705113

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分子动力学方法模拟不同温度下铀酰在叶腊石上的吸附和扩散行为

张陶娜1,徐雪雯1,董亮2,谭昭怡2,刘春立1,*()   

  1. 1 北京分子科学国家实验室,放射化学与辐射化学重点学科实验室,北京大学化学与分子工程学院,北京100871
    2 中国工程物理研究院核物理与化学研究所,四川绵阳621900
  • 收稿日期:2017-04-11 发布日期:2017-07-17
  • 通讯作者: 刘春立 E-mail:liucl@pku.edu.cn
  • 基金资助:
    高放废物地质处置专项资金(2007-840);高放废物地质处置专项资金(2012-851);国家自然科学基金(U1530112);国家自然科学基金(11475008);国家自然科学基金(11075006);国家自然科学基金(91026010)

Molecular Dynamics Simulations of Uranyl Species Adsorption and Diffusion Behavior on Pyrophyllite at Different Temperatures

Tao-Na ZHANG1,Xue-Wen XU1,Liang DONG2,Zhao-Yi TAN2,Chun-Li LIU1,*()   

  1. 1 Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry and Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
    2 Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, Sichuan Province, P. R. China
  • Received:2017-04-11 Published:2017-07-17
  • Contact: Chun-Li LIU E-mail:liucl@pku.edu.cn
  • Supported by:
    the Special Foundation for High-Level Radioactive Waste Disposal, China(2007-840);the Special Foundation for High-Level Radioactive Waste Disposal, China(2012-851);National Natural Science Foundation of China(U1530112);National Natural Science Foundation of China(11475008);National Natural Science Foundation of China(11075006);National Natural Science Foundation of China(91026010)

摘要:

采用分子动力学方法研究了铀酰在叶腊石表面的吸附和扩散。在碳酸根离子存在的情况下,探究了温度对铀酰吸附和扩散的影响。碳酸根离子与铀酰存在较强的作用力,不同数目的碳酸根离子与铀酰结合会形成多种铀酰种态。在不同温度的模拟中,得到了UO22+、UO2CO3、UO2(CO322-、UO2(CO334-四种铀酰种态和铀酰聚合物。通过原子密度图,观察了粒子在溶液中的分布情况。发现UO22+和UO2CO3容易吸附在叶腊石上,而UO2(CO322-和UO2(CO334-主要存在于扩散层中。随着时间的推移,越来越多的碳酸根离子与铀酰配位,使得铀酰在叶腊石上的吸附逐渐减少。本文计算了不同温度下,各铀酰种态的扩散系数。在扩散层中,各种态的扩散系数随温度的变化较为一致,而在吸附层中,UO22+和UO2CO3的扩散速率随温度的变化较UO2(CO322-和UO2(CO334-慢。但是在同一温度下,同一个吸附层或扩散层中,铀酰种态的扩散系数大小顺序始终保持不变:UO22+ > UO2CO3 > UO2(CO322- > UO2(CO334-。说明在碳酸根存在的情况下,UO22+可能是主要的扩散形式。

关键词: 叶腊石, 铀酰, 分子动力学模拟, 温度, 吸附, 扩散

Abstract:

In this study, molecular dynamics simulations were performed to gain insight into the adsorption and diffusion behavior of uranyl carbonate species on pyrophyllite basal surface at various temperatures (298.15, 313.15, and 333.15 K). At these temperatures, four kinds of uranium species, i.e. UO22+, UO2CO3, UO2(CO3) 22-, UO2(CO3) 34-, and uranyl oligomers were obtained. According to the atomic density profile of each uranyl species, only UO22+ and UO2CO3 were adsorbed on the pyrophyllite surface. Therefore, due to the strong coordination interaction between carbonate ion and uranyl, the pyrophyllite surface exhibited weak adsorption capacity for uranium after prolonged simulations. Self-diffusion coefficients of water molecules and uranyl species in both the adsorbed layer and the diffuse layer were calculated. With increasing temperature, the diffusion coefficients for all species increased; however, in the adsorbed layer, the diffusion coefficients for UO2(CO3) 22- and UO2(CO3) 34- increased faster than those for UO22+ and UO2CO3. Nonetheless, the diffuse order remained unchanged in both the layers: UO22+ > UO2CO3 > UO2(CO3) 22- > UO2(CO3) 34-. This indicates that UO22+ is the main diffusing species.

Key words: Pyrophyllite, Uranyl, Molecular dynamic simulation, Temperature, Adsorption, Diffusion

MSC2000: 

  • O643