核化学与放射化学2024，Vol.46Issue(6)：594-604,11.DOI:10.7538/hhx.2024.46.06.0594
含铀废水中[UO2(OH)m(H2O)n]2-m形态的模拟计算
Investigation of Configurations of[UO2(OH)m(H2O)n]2m in Uranium Wastewater
摘要
Abstract
Uranium-containing wastewater from the spent nuclear fuel are radioactive wastes as well as energy sources.It is meaningful to investigate the configurations of aqueous U(Ⅵ)for its environmental migrations and configuration conversions.Herein the uranyl complexes of[UO2(OH)m(H2O)n]2-m(m=1-4,n=1-2)were investigated by density functional theory at the PBE0 level,in combination with ECP80MWBAVQZ+2f basis set for uranium and 6-311+G**basis set for hydrogen and oxygen.The optimized geometries,energies,formation processes and thermodynamic properties of the complexes were predicted.In the six coordinated complexes that are spontaneously produced,the ligand numbers of OH-and H2O are 4 and 2,respectively.There exist either linear or"Ⅴ"configurations,sorting by the angles of Oyl-U-Oyl,when a linear uranyl dication coordinated with H2O and hydroxyl.The"Ⅴ"type complexes with Oyl-U-Oyl angle being about 40° are found only when the coordinated number of OH-is more than 2.The total energy of"Ⅴ"type[UO2(OH)3]-is lower than that of its linear isomer by 131.46 kJ/mol at the MP2 level.The complexes with U-OH2 bond and"Ⅴ"type Oyl-U-Oyl are the most stable.The complexes tend to have a"Ⅴ"configuration when the coordinated hydroxyl number is 3 or 4.The lengths of U-Oyl bond increase as the angles of Oyl-U-Oyl decrease.The complexes tend to be cage-like as more hydroxyl and H2O are coordinated.When UO2+coordinates with OH-one by one,a large amount of energy is released initially.As the coordinated number increases,the released energy dramatically decreases or even changes to an energy adsorbing process.When UO2+coordinates with H2O one by one,the processes release a small amount of energy continuously.The increase of H2O ligand is beneficial to the stability of the complexes.The formations of[UO2(OH)m]2-m(m＜4)are spontaneous processes.However,for the formation of[UO2(OH)4]2-,only the process of linear[UO2(OH)3]-converting to"Ⅴ"type[UO2(OH)4]2-is spontaneous,indicating the complexes tend to form"V"configuration when the number of OH-is 4.The spontaneous pathways and energy changes in the stepwise coordination processes were speculated on the basis of energy analysis.The above characteristics of[UO2(OH)m(H2O)n]2-m play an important role on the ion activity,solubility and ion exchange of uranyl in alkaline solutions.OH-and H2O compete with each other in coordinating,which influences the concentration and species distribution of[UO2(OH)m(H2O)n]2-m configurations.The results herein provide theoretical basis for understanding and controlling the behaviors and reactions of uranyl aqueous solutions.关键词
乏燃料/铀处理/铀酰离子/密度泛函理论/热力学性质Key words
spent nuclear fuel/uranium reprocessing/uranyl ion/density functional theory/thermody-namic分类
能源科技引用本文复制引用
曾秀琳,田孟克,唐双凌,居学海..含铀废水中[UO2(OH)m(H2O)n]2-m形态的模拟计算[J].核化学与放射化学,2024,46(6):594-604,11.基金项目
国家自然科学基金资助项目(21101070) （21101070）
乏燃料后处理科研专项(1161020387) （1161020387）
