Thermodynamics of trivalent actinides and neodymium in NaCl, MgCl2, and CaCl2 solutions: Solubility, hydrolysis, and ternary Ca-M(III)-OH complexes
Thermodynamics of trivalent actinides and neodymium in NaCl, MgCl2, and CaCl2 solutions: Solubility, hydrolysis, and ternary Ca-M(III)-OH complexes
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DOI：
10.1351/pac-con-08-09-05
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发表时间：
2009-09-01
影响因子：
1.8
通讯作者：
Fanghaenel, Thomas
中科院分区：
文献类型：
--
作者：
Neck, Volker;Altmaier, Marcus;Fanghaenel, Thomas
关于Am（OH）（3）（s）的溶解度以及Am（III）和Cm（III）的水解的已知数据，来自Nd（OH）（3）（s）在NaCl、MgCl 2和CaCl 2中的广泛溶解度研究的额外信息，各种离子强度的介质和光谱（时间分辨激光荧光光谱，TRLFS）数据的Cm（III）在碱性氯化钙，解决方案是用来评估一套全面的标准态平衡常数和离子相互作用参数的特定离子相互作用理论（SIT）和Pitzer方程在25摄氏度。热力学模型考虑到类似的三价锕系元素和Nd（III）的溶解度和水解行为，并涵盖了整个pH范围内的稀释到浓缩的NaCl，MgCl 2，CaCl 2，解决方案。在碱金属氯化物/氢氧化物溶液中，四氢氧化物络合物M（OH）（4）（-）的形成需要OH-浓度高于3 mol l（-1），而在碱性CaCl 2溶液（pH（c）< 12）中，形成具有四个和六个氢氧化物配体的M（III）络合物。与最近检测到的三元Ca-M（IV）-OH络合物Ca-3[Zr（OH）（6）]（4+）和Ca-4[Th（OH）（8）]（4+）类似，这些络合物通过Ca 2+离子的缔合而稳定。Am（III）、Cm（III）和Nd（III）在无Ca和含Ca溶液中的溶解度和水解一致地用包括三元Ca-M（III）-OH络合物Ca[M（OH）（3）]（2+）、Ca-2[M（OH）（4）]（3+）和Ca-3[M（OH）（6）]（3+）的模型描述。
Known data on the solubility of Am(OH)(3)(s) and the hydrolysis of Am(III) and Cm(III), additional information from an extensive solubility study with Nd(OH)(3)(s) in NaCl, MgCl2, and CaCl2, media of various ionic strengths and spectroscopic (time-resolved laser fluorescence spectroscopy, TRLFS) data for Cm(III) in alkaline CaCl2, solutions are used to evaluate a comprehensive set of standard-state equilibrium constants and ion interaction parameters for the specific ion interaction theory (SIT) and Pitzer equations at 25 degrees C. The thermodynamic model takes into account the analogous solubility and hydrolysis behavior of trivalent actinides and Nd(III) and covers the entire pH range in dilute to concentrated NaCl, MgCl2, and CaCl2, solutions. In alkali chloride/hydroxide solutions, the formation of the tetrahydroxide complex M(OH)(4)(-) requires OH- concentration above 3 mol l(-1), whereas in alkaline CaCl2, solutions (at pH(c) < 12) M(III) complexes with four and six hydroxide ligands are formed. Similar as the recently detected ternary Ca-M(IV)-OH complexes Ca-3[Zr(OH)(6)](4+) and Ca-4[Th(OH)(8)](4+), these complexes are stabilized by the association of Ca2+ ions. The solubility and hydrolysis of Am(III), Cm(III), and Nd(III) in both Ca-free and -containing solutions is consistently described with a model including the ternary Ca-M(III)-OH complexes Ca[M(OH)(3)](2+), Ca-2[M(OH)(4)](3+), and Ca-3[M(OH)(6)](3+).