ICSM, CEA, CNRS, ENSCM, Univ Montpellier, Bagnols sur Cèze Cedex, France.
Dalton Trans. 2018 Oct 23;47(41):14594-14603. doi: 10.1039/c8dt03140a.
The selective extraction of uranium by N-octylcalix[4]azacrown (NOCAC) and N-ethylhexylcalix[4]azacrown (NEHCAC) was investigated. The ligands were synthesised in three steps through the functionalisation of t-butyl calix[4]arene at the distal-1,3-positions of the lower rim with ethyl acetate groups followed by cyclisation with (imino)bis(ethane-2,1-diyl)diamide. A detailed investigation on the effect of various parameters, such as the aqueous phase acidity (sulfuric acid), the ionic strength, and ligand concentration, on the extraction of uranium(vi) has been conducted. The effect of the H2SO4 concentration has been studied from 0.02 to 3 M. Preliminary studies carried out on NOCAC in dodecane/octanol diluents showed that the uranium extraction from sulfuric acid is more efficient at a low H2SO4 concentrations. The stoichiometry of complexation was estimated from the slope method, NMR titration, and electrospray ionisation-mass spectrometry analysis. Both ligands were found to be highly selective for uranium(vi) over other competitive cations present in a simulated leach solution containing seven competitive cations. The successful recovery of the uranium from the organic phase has been performed thanks to stripping steps involving ammonium oxalate, ammonium carbonate, and sodium carbonate as stripping agents.
用 N-辛基杯[4]氮杂冠醚（NOCAC）和 N-乙基己基杯[4]氮杂冠醚（NEHCAC）对铀的选择性萃取进行了研究。配体通过在叔丁基杯[4]芳烃下边缘的 1,3-位上用乙酸乙酯基团官能化，然后与（亚氨基）双（乙烷-2,1-二基）二酰胺环化来合成。详细研究了各种参数对萃取六价铀的影响，如水相酸度（硫酸）、离子强度和配体浓度。研究了 H2SO4 浓度从 0.02 到 3 M 的影响。在十二烷/辛醇稀释剂中对 NOCAC 进行的初步研究表明，在低 H2SO4 浓度下，从硫酸中萃取铀的效率更高。通过斜率法、NMR 滴定和电喷雾电离质谱分析估算了络合的化学计量比。发现两种配体对模拟浸出液中存在的七种竞争性阳离子中的铀（VI）都具有很高的选择性。通过使用草酸铵、碳酸铵和碳酸钠作为洗脱剂进行洗脱步骤，成功地从有机相中回收了铀。
