Onghena Bieke, Papagni Eleonora, Souza Ernesto Rezende, Banerjee Dipanjan, Binnemans Koen, Vander Hoogerstraete Tom
KU Leuven, Department of Chemistry, Celestijnenlaan 200F, Bus 2402, B-3001 Heverlee, Belgium. Email:
RSC Adv. 2018 Sep 17;8(56):32044-32054. doi: 10.1039/c8ra06712k. Epub 2018 Sep 14.
A speciation study was carried out for lanthanide complexes formed in the organic phase after solvent extraction with quaternary ammonium and phosphonium nitrate extractants. These extractants are liquid at room temperature and were applied in their undiluted form. A comparison was made between the quaternary compound trihexyl(tetradecyl)phosphonium nitrate, the nitrate form of the commercial extractant Cyphos IL 101, and Aliquat 336 nitrate, the nitrate form of the commercial trialkylmethylammonium chloride extractant Aliquat 336 (alkyl = mixture of C8 and C10 chains). The structures of the lanthanide complexes across the entire lanthanide series (with the exception of promethium) were determined by a combination of solvent extraction techniques, FTIR, NMR, high-resolution steady-state luminescence spectroscopy, luminescence life time measurements, elemental analysis and EXAFS spectroscopy. The results suggest that the lanthanide ions form an anionic nitrate complex in the organic phase by coordinating with five bidentate nitrate ligands. Charge neutralization is provided by two counter cations of the extractant present in the outer coordination sphere of the complex. Furthermore, it is suggested that the pentanitrato complex is the sole lanthanide species that is formed in significant concentrations in the organic phase.
采用硝酸季铵盐和硝酸鏻盐萃取剂进行溶剂萃取后，对有机相中形成的镧系元素配合物开展了物种形成研究。这些萃取剂在室温下为液体，以未稀释形式使用。对季铵化合物三己基（十四烷基）硝酸鏻、商业萃取剂Cyphos IL 101的硝酸盐形式以及Aliquat 336硝酸盐（商业三烷基甲基氯化铵萃取剂Aliquat 336的硝酸盐形式，烷基 = C8和C10链的混合物）进行了比较。通过溶剂萃取技术、傅里叶变换红外光谱（FTIR）、核磁共振（NMR）、高分辨率稳态发光光谱、发光寿命测量、元素分析和扩展X射线吸收精细结构光谱（EXAFS）相结合的方法，确定了整个镧系元素系列（除钷外）的镧系元素配合物结构。结果表明，镧系离子通过与五个双齿硝酸根配体配位，在有机相中形成阴离子硝酸根配合物。电荷中和由配合物外配位层中存在的两个萃取剂抗衡阳离子提供。此外，有人认为五硝酸根配合物是在有机相中以显著浓度形成的唯一镧系物种。
