【摘要】：粘土礦物在土壤和沉積物中廣泛存在。其獨特的物理和化學性質,比如較大的比表面積、膨脹性、陽離子交換能力、還有依賴pH的吸附能力等,使其成為重要的吸附材料。隨著實際應用的需要和科學研究的深入,人們需要越來越多的原子分子層次上的微觀信息。盡管目前大量先進的實驗設備和近似理論都被應用到粘土礦物的研究當中,然而,目前的實驗手段仍不能提供充分的微觀信息以滿足各個領域的需求。計算機模擬方法可以彌補這些不足,對這些微觀信息作出預測。本論文利用計算模擬探究了鈾酰在粘土礦物表界面上的吸附,主要包括鈾酰及鈾酰-碳酸絡合物在粘土礦物表面上的吸附。首先,采用經典分子動力學模擬我們探究了鈾酰及鈾酰-碳酸根絡合物在葉臘石、高嶺石和蒙脫石基面上的吸附狀況。結果表明,鈾酰只在硅氧烷面形成外球吸附,而一碳酸合鈾酰絡合物則在硅氧烷面和鋁氧層面均可形成外球吸附。二碳酸合鈾酰絡合物和三碳酸合鈾酰絡合物可以在鋁氧層面上形成穩(wěn)定的外球吸附。鈾酰及鈾酰絡合物在兩種基面上通過不同的形式形成外球吸附:硅氧烷面上通過靜電作用,鋁氧層面上通過氫鍵作用。然后,作為進一步研究,我們利用第一性原理分子動力學研究了鈾酰及鈾酰-碳酸絡合物在2:1型粘土礦物(010)面上的吸附位置及吸附結構。我們主要關注了(010)面上兩個吸附位置:≡Al(OH)_2和≡SiO。結果顯示,鈾酰及其碳酸絡合物在這兩個位置均可以形成穩(wěn)定的雙齒絡合的吸附結構,所形成的表面絡合物分別為≡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,二碳酸合鈾酰絡合物在≡SiO位置上吸附時,兩個配位碳酸根與鈾酰的結合方式不一樣,一個單齒絡合,一個雙齒絡合,這使得鈾酰最終的配位數(shù)為5。通過本論文的研究,我們系統(tǒng)的探究了鈾酰及鈾酰-碳酸絡合物在粘土礦物表面上的吸附行為,揭示了其在粘土礦物不同表面上的吸附形式和微觀結構。
[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，

本文編號：2151151