A novel strategy for water content analysis in (B12C4/B15C5/B18C6-[EMIm][NTf2])-LiNTf2 extraction system: Quantitative calculation and theoretical study

The metal ion extraction process   is usually accompanied   by the removal of coordinated water molecules and the change of water content in the extraction phase. However, hierarchical methodologies on water research   are incredibly sparse, restricting a thorough knowledge of the extraction mechanism.   It was clarified the diversity of water occurrence forms in the extraction phase and quantitative relationship between water, Li + and crown ether based on the (B12C4/B15C5/B18C6-[EMIm][NTf 2 ])-LiNTf 2 solvent extraction system. While the complexation mechanism between hydrated Li + and crown ether was discussed carefully. Firstly, it demonstrated that the water content of the extraction phase: B18C6 > B15C5 > B12C4. Secondly,   the water in the extraction phase is mainly collected by solvent and crown ether, with the latter catching water primarily via Li + coordination and weak interactions. In the end, focusing on the water captured by the crown ether through Li + coordination, slope analysis and DFT calculations found that Li (H 2 O) 4 + was removed three water molecules to complex with B12C4 or B15C5, whereas B18C6 tends to remove two water molecules. It is precious for a thorough grasp of the mechanism and procedure of Li + extraction by crown ethers. What’s more, it offers novel strategies for investigating water content and transfer mechanisms in extraction systems.