粘土矿物—水界面上铀酰吸附的计算模拟研究
发布时间：2018-07-28 17:58
【摘要】：粘土矿物在土壤和沉积物中广泛存在。其独特的物理和化学性质,比如较大的比表面积、膨胀性、阳离子交换能力、还有依赖pH的吸附能力等,使其成为重要的吸附材料。随着实际应用的需要和科学研究的深入,人们需要越来越多的原子分子层次上的微观信息。尽管目前大量先进的实验设备和近似理论都被应用到粘土矿物的研究当中,然而,目前的实验手段仍不能提供充分的微观信息以满足各个领域的需求。计算机模拟方法可以弥补这些不足,对这些微观信息作出预测。本论文利用计算模拟探究了铀酰在粘土矿物表界面上的吸附,主要包括铀酰及铀酰-碳酸络合物在粘土矿物表面上的吸附。首先,采用经典分子动力学模拟我们探究了铀酰及铀酰-碳酸根络合物在叶腊石、高岭石和蒙脱石基面上的吸附状况。结果表明,铀酰只在硅氧烷面形成外球吸附,而一碳酸合铀酰络合物则在硅氧烷面和铝氧层面均可形成外球吸附。二碳酸合铀酰络合物和三碳酸合铀酰络合物可以在铝氧层面上形成稳定的外球吸附。铀酰及铀酰络合物在两种基面上通过不同的形式形成外球吸附:硅氧烷面上通过静电作用,铝氧层面上通过氢键作用。然后,作为进一步研究,我们利用第一性原理分子动力学研究了铀酰及铀酰-碳酸络合物在2:1型粘土矿物(010)面上的吸附位置及吸附结构。我们主要关注了(010)面上两个吸附位置:≡Al(OH)_2和≡SiO。结果显示,铀酰及其碳酸络合物在这两个位置均可以形成稳定的双齿络合的吸附结构,所形成的表面络合物分别为≡Al(OH)_2-UO_2-(H_2O)3、≡Al(OH)_2-UO_2-(CO_3)(H_2O)、≡Al(OH)_2-UO_2-(CO_3)_2、≡(SiO)(AlOH)-UO_2-(H_2O)3、≡(SiO)(AlOH)-UO_2-(CO_3)(H_2O)和≡(SiO)(AlOH)-UO_2-(CO_3)_2。其中,二碳酸合铀酰络合物在≡SiO位置上吸附时,两个配位碳酸根与铀酰的结合方式不一样,一个单齿络合,一个双齿络合,这使得铀酰最终的配位数为5。通过本论文的研究,我们系统的探究了铀酰及铀酰-碳酸络合物在粘土矿物表面上的吸附行为,揭示了其在粘土矿物不同表面上的吸附形式和微观结构。
[Abstract]:Clay minerals are widely found in soils and sediments. Its unique physical and chemical properties, such as large specific surface area, expansibility, cation exchange ability and pH dependent adsorption ability, make it an important adsorption material. With the need of practical application and the deepening of scientific research, more and more micro information on atomic and molecular level is needed. Although a large number of advanced experimental equipment and approximate theories have been applied to the study of clay minerals, the present experimental methods are still unable to provide sufficient micro information to meet the needs of various fields. Computer simulation method can make up for these shortcomings and predict these micro information. In this paper, the adsorption of uranyl on the surface of clay minerals was investigated by computer simulation, including the adsorption of uranyl and uranyl-carbonate complex on the surface of clay minerals. Firstly, the adsorption of uranyl and uranyl-carbonate complexes on pyrophyllite, kaolinite and montmorillonite was investigated by classical molecular dynamics simulation. The results show that uranyl is adsorbed only on the surface of siloxane, while uranyl carbonate can be adsorbed on the surface of siloxane and aluminum oxide. The complex of uranyl bicarbonate and uranyl tricarbonate can form stable outer sphere adsorption on the aluminum-oxygen layer. Uranyl and uranyl complexes are adsorbed by different forms on two basic surfaces: electrostatic interaction on siloxane surface and hydrogen bonding on aluminum and oxygen plane. Then, as a further study, the adsorption sites and structures of uranyl and uranyl-carbonate complexes on the 2:1 clay minerals (010) were investigated by first-principles molecular dynamics. We mainly focus on two adsorption sites on the (010) surface: 鈮，
本文编号：2151151
[Abstract]:Clay minerals are widely found in soils and sediments. Its unique physical and chemical properties, such as large specific surface area, expansibility, cation exchange ability and pH dependent adsorption ability, make it an important adsorption material. With the need of practical application and the deepening of scientific research, more and more micro information on atomic and molecular level is needed. Although a large number of advanced experimental equipment and approximate theories have been applied to the study of clay minerals, the present experimental methods are still unable to provide sufficient micro information to meet the needs of various fields. Computer simulation method can make up for these shortcomings and predict these micro information. In this paper, the adsorption of uranyl on the surface of clay minerals was investigated by computer simulation, including the adsorption of uranyl and uranyl-carbonate complex on the surface of clay minerals. Firstly, the adsorption of uranyl and uranyl-carbonate complexes on pyrophyllite, kaolinite and montmorillonite was investigated by classical molecular dynamics simulation. The results show that uranyl is adsorbed only on the surface of siloxane, while uranyl carbonate can be adsorbed on the surface of siloxane and aluminum oxide. The complex of uranyl bicarbonate and uranyl tricarbonate can form stable outer sphere adsorption on the aluminum-oxygen layer. Uranyl and uranyl complexes are adsorbed by different forms on two basic surfaces: electrostatic interaction on siloxane surface and hydrogen bonding on aluminum and oxygen plane. Then, as a further study, the adsorption sites and structures of uranyl and uranyl-carbonate complexes on the 2:1 clay minerals (010) were investigated by first-principles molecular dynamics. We mainly focus on two adsorption sites on the (010) surface: 鈮，
本文编号：2151151
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