A combined DFT and molecular dynamics study of U（VI）/calcite interaction in aqueous solution

• Published in: 科学通报：英文版 Vol. 62; no. 15; pp. 1064 - 1073
• Main Author: Jian-Hui Lan Zhi-Fang Chai Wei-Qun Shi
• Format: Journal Article
• Language: English
• Published: 2017
• Subjects: DFT; 分子动力学; 方解石; 水溶液; 相互作用机制; 离子交换反应; 表面络合物
• ISSN: 2095-9273

Here we present a combined DFF and molecular dynamics study of uranyl （U（VI）） interaction mecha- nisms with the calcite （104） surface in aqueous solution. The roles of three anion ligands （CO2 , HCO3, OH ） and solvation effect in U（VI） interaction with calcite have been evaluated. According to our calculations, water adsorbed on the calcite （104） surface prefers to exist in molecular state rather than dis- sociative state. Energy analysis indicate that the positively charged uranyl species prefers to form surface complexes on the surface, while neutral uranyl species may bind with the surface via both surface complexing and ion exchange reactions of U（VI） → Ca（II）. In contrast, the negatively charged uranyl species prefer to interact with the surface via ion exchange reactions of U（VI）→ Ca（II）, and the one with UO2（CO3）2（H2O）^2- as the reactant becomes the most favorable one in energy. We also found that uranyl adsorption increases the hydrophilicability of the （104） surface to different extents, where the UO2（CO3）3Ca2 species contributes to the largest degree of energy changes （ 53 kcal/mol）. Our calcula- tions proved that the （104） surface also has the ability to immobilize U（VI） via either surface complexing or ion exchange mechanisms under different pH values.