含铀废水中[UO_(2)(OH)_(m)(H_(2)O)_(n)]^(2-m)形态的模拟计算  

Investigation of Configurations of[UO_(2)(OH)_(m)(H_(2)O)_(n)]^(2-m)in Uranium Wastewater

作　　者：曾秀琳 田孟克 唐双凌[2] 居学海[2] ZENG Xiu-lin;TIAN Meng-ke;TANG Shuang-ling;JU Xue-hai(School of Chemistry and Materials Engineering,Huainan Normal University,Huainan 232038,China;School of Chemistry and Chemical Engineering,School of Environmental and Biochemical Engineering,Nanjing University of Science and Technology,Nanjing 210094,China)

机构地区：[1]淮南师范学院化学与材料工程学院,安徽淮南232038 [2]南京理工大学化学与化工学院,环境与生物工程学院,江苏南京210094

出　　处：《核化学与放射化学》2024年第6期594-604,I0004,共12页Journal of Nuclear and Radiochemistry

基　　金：国家自然科学基金资助项目(21101070);乏燃料后处理科研专项(1161020387)。

摘　　要：乏燃料含铀废水既是放射性污染物,也是可回收利用的铀资源。U(Ⅵ)在水溶液中的化学形态对其在环境中的迁移性和溶液的形态转化调控有重要意义。采用密度泛函理论方法计算研究铀酰离子与羟基和水形成配合物的结构和性质,求得优化几何构型、能量、形成过程和热力学性质。自发生成的6配位配合物中,羟基和水的配位数分别是4和2。直线型铀酰阳离子同羟基和水形成配合物,按Oyl-U-Oyl(Oyl表示酰基氧)角度不同,存在线型和“V”型两种构型。分子式相同时,铀酰基团的U-Oyl,键长随着Oyl-U-Oyl角度的减小而增长。随着OH^(-)和H_(2)O配体数增加,配合物的结构趋于笼状;当OH^(-)配体数为3或4时,倾向于生成“V”型铀酰配合物。逐级生成[UO_(2)(OH)_(m)]^(2-m)配合物时,开始释放出大量的能量,但是随着OH配位数增加,释放的能量急剧减少,直至吸收能量。而逐级生成[UO_(2)(H_(2)O)_(n)]^(2+)配合物时,则持续释放出少量能量;H2O配体数增加时有利于形成稳定配合物。生成[UO_(2)(OH)_(m)]^(2-m)(m<4)配合物的反应能自发进行;而生成[UO_(2)(OH)_(4)]^(2-)配合物的反应,仅线型[UO_(2)(OH)_(3)]^(-)生成“V”型[UO_(2)(OH)_(4)]^(2-)是自发过程。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[UO_(2)(OH)_(m)(H_(2)O)_(n)]^(2-m)(m=1-4,n=1-2)were investigated by density functional theory at the PBEO level,in combination with ECP80MWB_AVQZ+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 H_(2)O are 4 and 2,respectively.There exist either linear or“v”configurations,sorting by the angles of O_(yl)-U-O_(yl),when a linear uranyl dication coordinated with H_(2)O and hydroxyl.The“V”type complexes with O_(yl)-U-O_(yl) angle being about 40°are found only when the coordinated number of OH^(-) is more than 2.The total energy of“V”type[UO_(2)(OH)_(3)]^(-)is lower than that of its linear isomer by 131.46 kJ/mol at the MP2 level.The complexes with U-OH_(2)bond and“V”type O_(yl)-U-O_(yl) 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-O_(yl) bond increase as the angles of O_(yl)-U-O_(yl) decrease.The complexes tend to be cage-like as more hydroxyl and H_(2)O are coordinated.When UO_(2)^(2+)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 UO_(2)^(2+)coordinates with H_(2)O one by one,the processes release a small amount of energy continuously.The increase of H_(2)O ligand is beneficial to the stability of the complexes.The formations of[UO_(2)(OH)_(m)]^(2-m)(m<4)are spontaneous processes.However,for the formation of[UO_(2)(OH)_(4)]^(2-),only the process of linear

关 键 词：乏燃料 铀处理 铀酰离子 密度泛函理论 热力学性质 

分 类 号：TL941.1[核科学技术—辐射防护及环境保护] O064[理学]