ABSTRACT

This paper reports the liquid-liquid extraction behavior of lithium ions from aqueous solutions containing hydrochloric acid using a well-known neutral extractant tri-n-butyl phosphate (TBP) and commonly used imidazolium-based ionic liquids (IL). The effect of several experimental parameters on the lithium partitioning was examined, in particular the nature of counter anions, the concentration of TBP, the pH of the aqueous solutions, and the initial lithium ion concentration. The lithium extraction was also investigated with a conventional organic solvent 1-octanol to understand the role of the IL in the extraction process. Our results suggest that lithium partition into TBP/IL system proceeds via two mechanisms, namely by cationic exchange and ion pair transfer. The corresponding extraction equilibrium constants as well as stoichiometry of extracted complexes were determined. To overcome the loss of ionic liquid by cation exchange, we have shown that TBP mixed with an ionic liquid possessing low solubility in aqueous phases can extract lithium when a highly hydrophobic counter-ion such as ($\mathrm{T}{\mathrm{f}}_2{\mathrm{N}}^{-}$) is present in the aqueous phase.

摘要

本文报道使用公知的中性萃取三含有盐酸的水溶液的锂离子的液-液萃取行为Ñ丁基磷酸酯（TBP）和常用的基于咪唑鎓的离子液体（IL）。检查了几个实验参数对锂分配的影响，特别是抗衡阴离子的性质，TBP的浓度，水溶液的pH值和初始锂离子浓度。还使用常规有机溶剂1-辛醇研究了锂的萃取过程，以了解IL在萃取过程中的作用。我们的结果表明，锂通过以下方式进入TBP / IL系统：两种机理，即通过阳离子交换和离子对转移。确定了相应的提取平衡常数以及提取的配合物的化学计量。为了克服由于阳离子交换而造成的离子液体的损失，我们已经证明，TBP与在水相中具有较低溶解度的离子液体混合可以在高度疏水的抗衡离子（如（$\mathrm{Ť}{\mathrm{F}}_2{\mathrm{ñ}}^{-}$）存在于水相中。