Distribution of benzo-substituted crown-ethers between chloroform and water: effects of macrocycle ring size and lithium chloride

Study of Lithium-Extraction Systems Based on Benzo-15-Crown-5 Ether and Alkylimidazolium-Based Ionic Liquid

The extraction of lithium from aqueous solutions of LiNTf₂ and LiCl salts using benzo-15-crown-5 ether (B15C5) as an extractant in [C8mim][NTf₂] ionic liquid was studied. The transition of the extractant into the aqueous phase and the distribution of Cl^- ions during lithium extraction from LiCl solutions were determined. LiNTf₂ complexes with B15C5 with different LiNTf₂:B15C5 ratios were isolated for the first time and characterized via X-ray diffraction and IR spectroscopy. Differences in the extraction process of LiCl and LiNTf₂ were determined via an infrared spectroscopic study of the extraction systems.

A Highly Selective Polymer Material using Benzo-9-Crown-3 for the Extraction of Lithium in Presence of Other Interfering Alkali Metal Ions

The recovery of lithium from global water resources continues to be challenging due to interfering metal ions with similar solution properties. Hence, a lithium-selective diblock copolymer system containing crown ethers (CEs) is developed. A polystyrene-block-poly(methacrylic acid) diblock copolymer is synthesized first via a one-pot solution-emulsion reversible addition-fragmentation chain transfer polymerization. A subsequent Steglich esterification yields the CE functionalized polymer. The complexation properties with different alkali metals are first investigated by liquid-liquid extraction (LLE) in dichloromethane (DCM) - water systems using free benzo-9-crown (B9C3), benzo-12-crown-4 (B12C4), and benzo-15-crown-5 (B15C5) CEs as reference components, followed by the correspondingly CE-functionalized polymers. Extraction complexation constants in the aqueous phase are determined and the impact of the complexation constants on the extractability is estimated. The B9C3 CE is especially appealing since it has the smallest cavity size among all CEs. It is too small to complex sodium or potassium ions; however, it forms sandwich complexes with a lithium-ion resulting in extraordinary complexation constants in polymer systems avoiding other interfering alkali metal ions. On this basis, a new material for the efficient extraction of lithium ion traces in global water resources is established.

Highly Selective and Pollution-Free Electrochemical Extraction of Lithium by a Polyaniline/Lix Mn2 O4 Cell

Conventional lithium extraction processes are inefficient or inadaptable for application in salt-lake brines with high Mg/Li ratios of ≥6. A new electrochemical cell, polyaniline (PANI)/Li_x Mn₂ O₄ , was proposed to solve this problem for selective recovery of Li⁺ ions from brine water with high impurity cations (K⁺ , Na⁺ , Mg²⁺ , etc). Benefiting from the unique selectivity of spinel Li_x Mn₂ O₄ for Li⁺ insertion and the high capacity of the PANI polymer for Cl^- doping, this PANI/Li_x Mn₂ O₄ cell could simultaneously extract LiCl from a simulated brine with a high average current efficiency of 95 %, an energy consumption of 3.95 W h mol_LiCl ^-1 , and a strong cycle ability with 70.8 % capacity retention over 200 cycles. In particular, this method avoids the use of additional chemicals, offering a highly efficient, pollution-free technology for Li⁺ extraction from brine waters.