高放废物深地质处置库蒙脱土对铀酰的吸附阻滞行为：分子模拟研究

杨微; 陈仁朋; 康馨; ZaouiAli

doi:10.11779/CJGE202002004

高放废物深地质处置库蒙脱土对铀酰的吸附阻滞行为：分子模拟研究 English Version

杨微^{1, 2, 3,},
陈仁朋^{1, 2, 3, ,},
康馨^{1, 2, 3},
ZaouiAli⁴

1.
湖南大学建筑安全与节能教育部重点实验室,湖南　长沙　410082
2.
湖南大学建筑安全与环境国际联合研究中心,湖南　长沙　410082
3.
湖南大学土木工程学院,湖南　长沙　410082
4.
University of Lille 1-Science and Technology, Lille 59000, France

基金项目:

国家自然科学基金项目 41807261

国家自然科学基金项目 51808207

国家自然科学基金项目 51608188

国家自然科学基金项目 51938005

湖南省新型省份建设专项经费项目 2019RS1030

详细信息

作者简介:
杨微（1986— ）,女,博士,副教授,主要从事分子动力学土体微细观力学、重金属污染处置及放射性核废料阻滞吸附研究工作。E-mail：yangwei86@hnu.edu.cn

通讯作者:
陈仁朋, E-mail：chenrp@hnu.edu.cn

中图分类号: TU43
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出版历程
- 收稿日期: 2018-11-12
- 网络出版日期: 2022-12-07
- 刊出日期: 2020-01-31

Radionuclide adsorption mechanism in buffer materials in high-level radioactive waste container: MD study

YANG Wei^{1, 2, 3,},
CHEN Ren-peng^{1, 2, 3, ,},
KANG Xin^{1, 2, 3},
Zaoui Ali⁴

1.
Key Laboratory of Building Safety and Energy Efficiency of Ministry of Education, Hunan University, Changsha 410082
2.
National Center for International Research Collaboration in Building Safety and Environment, Hunan University, Changsha 410082
3.
College of Civil Engineering, Hunan University, Changsha 410082, China
4.
University of Lille 1-Science and Technology, Lille 59000, France

摘要

摘要: 核废料处置库在长期运行过程中,地下水渗流会引起膨润土缓冲层水化学环境改变。运用分子动力学模拟方法,揭示含蒙脱土的膨润土缓冲材料对放射性核素铀酰的吸附机理及吸附复合物微观结构。模拟得到的复合物结构展现了铀酰与蒙脱土面的3种主要吸附模式：外球吸附、单键内球吸附、双键内球吸附。定量分析了在复杂水化学环境下3种铀酰种态与蒙脱土表面形成的复合物微观结构组成。通过计算复合物与蒙脱土表面的吸附能,发现高价阳离子和碳酸根离子的存在可以促进铀酰与缓冲材料表面形成稳定吸附。
- 分子动力学 /
- 放射性核素 /
- 铀酰 /
- 阻滞吸附 /
- 蒙脱土
Abstract: The buffer material plays a decisive role in preventing the radionuclide to enter into the host rock, as it is the last defense of engineered barrier system. Under very high groundwater pressure, a large amount of cations percolate through the barrier with underground water, resulting in a complicated chemical condition. Molecular dynamics simulation is performed to deeply investigate the adsorption mechanism of radionuclide species onto substituted montmorillonite (001) surface in the presence of different counterions. MD simulations exhibit three typical adsorption modes: outer-sphere complex, monodentate inner-sphere complex and bidentate inner-sphere complex. With the presence of carbonate ions and covalent cations, the U atom in uranyl can coordinate with carbonate oxygen in connection with cations to form an intensive adsorption complex with MMT surface. The thermodynamic work of adhesion between the complexes and the MMT surface is calculated to evaluate the adsorption interaction. The complexes with the carbonate and covalent cation components exhibit a relatively high adhesion with the buffer material surface.
- molecular dynamics /
- radionuclides /
- uranyl /
- adsorption /
- montmorillonite

HTML全文

图 1 蒙脱土-铀酰溶液相互作用结构初始图

Figure 1. Initial model for montmorillonite-uranyl solution interaction

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图 2 铀酰离子水化前及水化后的模型结构图

Figure 2. Snapshots of the Uranyl and hydrated uranyl structure

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图 3 铀酰溶液与蒙脱土片层结构

Figure 3. Uranyl solution and clay layers

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图 4 铀酰离子与蒙脱土表面形成的典型复合物结构示意图,包.含三中典型吸附：外球、单键内球及双键内球

Figure 4. Snapshot of representative adsorption complexes including three typical adsorptions: outer-sphere, mono-dentate and bidentate inner-sphere complex

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图 5 碳酸根及氯离子分别存在下,蒙脱土吸附形成的典型铀酰复合物结构示意图

Figure 5. Snapshot of optimized adsorption uranyl complexes on MMT (001) surface with presence of carbonate and chlorite

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图 6 铀酰在不同种态中与蒙脱土表面吸附形成复合物中铀原子与配位原子间的径向分布函数

Figure 6. Plot of U-ligand RDFs in presence of carbonate and chlorite

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表 1 水、蒙脱土、SPC/E水及铀酰种态中各原子电荷及CLAYFF力场范德华势能参数

Table 1 Charges and ClayFF force field parameters for water, cations, montmorillonite and radionuclides

原子符号	表示内容	电荷/e	$ε$ $ε$ /(kcal·mol^-1)	$σ$ $σ$ /Å
H_w	水中的氢	0.4100	0	0
O_w	水中的氧	-0.8200	0.1554	3.1655
h	土中羟基的氢	0.4250	0	0
oh	土中羟基的氧	-0.9500	0.1554	3.1655
ob	土中桥接四面体片硅和八面体片铝的氧	-1.0500	0.1554	3.1655
obos	土中桥接四面体片硅和八面体中同质替换镁的氧	-1.1808	0.1554	3.1655
obts	土中桥接四面体片中同质替换铝和八面体铝的氧	-1.1688	0.1554	3.1655
obss	土桥接四面体片中同质替换铝和八面体中同质替换镁的氧	-1.2996	0.1554	3.1655
ohs	土连接同质替代原子羟基中的氧	-1.0808	0.1554	3.1655
st	蒙脱土四面体片中硅	2.1000	1.8405×10^-6	3.3020
ao	土八面体片中铝	1.5750	1.3298×10^-6	4.2712
at	土四面体片中铝	1.5750	1.8405×10^-6	3.3020
mgo	土八面体片中镁	1.3600	9.0298×10^-6	5.2643
mgh	土八面体片中与羟基相连的镁	1.0500	9.0298×10^-6	5.2643
Na	层间阳离子钠	1.0	0.1301	2.3500
K	层间阳离子钾	1.0	0.1000	3.3340
Cs	层间阳离子铯	1.0	0.1000	3.8310
Ba	层间阳离子钡	2.0	0.0470	3.8166
Pb	层间阳离子铅	2.0	0.6650	3.4103
Ca	层间阳离子钙	2.0	0.1000	2.8719
Zn	层间阳离子锌	2.0	0.6650	2.1933
Cl	氯离子	-1.0	0.1001	4.3999
U	铀酰中的釉	2.5	0.4991	2.8221
O	铀酰中的氧	-0.25	0.1554	3.1655
C	碳酸根中的碳	0.43	0.0565	2.7570
Oc	碳酸根中的氧气	-0.81	0.1610	3.0330

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表 2 水、铀酰及酸根离子的电荷、键长及键角参数

Table 2 Charges, bond and angle parameters for water, uranyl and carbonate ions

键类型			k ₁/(kcal·mol^-1·Å^-2)	$r_{i j}^{0}$ $r_{i j}^{0}$ /Å
原子i	原子j		k ₁/(kcal·mol^-1·Å^-2)	$r_{i j}^{0}$ $r_{i j}^{0}$ /Å
O_w	H_w		554.1349	1.0000
U	O		554.1349	1.8000
C	O_c		652.0000	1.2500
键角类型			k ₂/(kcal·mol^-1·Å^-2)	$θ_{i j k}^{0}$ $θ_{i j k}^{0}$ /deg
原子i	原子j	原子k	k ₂/(kcal·mol^-1·Å^-2)	$θ_{i j k}^{0}$ $θ_{i j k}^{0}$ /deg
H_w	O_w	H_w	45.769	109.47
U	O	U	150.000	180.00
Oc	C	Oc	80.000	126.00

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表 3 单个铀酰种态分子与蒙脱土表面吸附产生典型吸附复合物的分子结构特征、范德华接触面积及吸附能

Table 3 Complex parameters, Van der Waals contact area and work of adhesion of single radionuclide adsorbed on MMT surface in presence of different cations

铀酰种态	复合物分子结构	U-Os个数	U-Oc个数	A/Å²	吸附能/(J·m^-2)
[UO₂(H₂O)₅]²⁺	[UO₂(H₂O)₅]²⁺			56.681	0.852
	[UO₂(H₂O)₄(O_s)]²⁺	1		30.067	1.259
	[UO₂(H₂O)₃(O_s)₂]²⁺	2		25.942	1.861
[UO₂(H₂O)₅Cl₂]	[Na₂UO₂(H₂O)₃Cl₂]²⁺			39.858	0.610
	[NaUO₂(H₂O)₄Cl]²⁺			31.063	1.119
	[NaUO₂(H₂O)₃(O_s)₂Cl]²⁺	2		38.722	0.718
[UO₂(H₂O)₅CO₃]	[CsUO₂(H₂O)₂CO₃(O_s)]⁺	1	2	38.722	1.172
	[BaUO₂(H₂O)CO₃(O_s)]²⁺	1	3	31.691	1.502
	[CaUO₂(H₂O)₂CO₃(O_s)]²⁺	1	2	33.586	2.348
	[ZnUO₂(H₂O)₂CO₃]²⁺		1	38.849	1.851

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