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本文研究了不同酯烷基结构的异丙基膦酸单烷基酯萃取稀土反应的平衡常数(K_(ex))的差别。异丙基膦酸单β-取代烷基酯具有较高K_(ex)值,而相应的α-取代烷基酯的K_(ex)值则显著下降。此外,镧系收缩的特性扩大了配位体的空间效应,这类效应对化合物的pKa值也有影响。并讨论了异丙基膦酸单十四烷基酯(MANPP)萃取稀土的反应机理,测得该反应的热力学函数,不论K_(ex)值或△G值与原子序数间均具四分组效应。研究了萃取配合物的组成与结构,值得指出的是MANPP在盐酸体系中萃取分离钕、钐的性能均优于硝酸体系。 相似文献
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Dialkyl isopropylphosphonates with various alkyl groups are synthesized for the structure-reactivity studies on the extraction of rare earths. Steric effect of ligands on the extrac-tion behaviour of rare earth is well demonstrated due to the lanthanide contraction. Thethermodynamic functions of the extraction reaction are estimated and the influence of chem-ical structure of extractants is discussed. By the method of continuous variation as well asthe elementary analysis, the composition of the extracted species is deduced as Ln(NO_3)_3·3L.The structure of the coordination compound is further elucidated by IR and NMR spectra.The magnetic property and the differential thermal analysis of the complexes are also studied. 相似文献
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The influence of chemical structure of ester alkyl group of mono-alkyl isopropylphosphonates on the extraction behaviours of rare earth has been studied. The mono-alkyl isopropylphosphonate bearing β-substituted ester alkyl group shows high K_(ex) value, which is evidently depressed, usually in two orders of magnitude, by introducing a branch chain on the α-position of the ester alkyl group. The steric effect of ligand is usually enhanced due to the characteristic lanthanide contraction.z2The extraction chemistry of rare earths by mono-amylnonyl isopropylphosphonates (MANPP) was studied in detail The thermodynamic function was estimated and the "tetrad effect" between K_(ex) value or △G value and atomic number was observed. In addition, the composition and structure of the coordinated compound was studied. As demonstrated by the experimental data, the extractive separation of Sm and Nd by MANPP in chloride solution was better than that in nitrate system. 相似文献
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