Selective Solid–Liquid and Liquid–Liquid Extraction of Lithium Chloride Using Strapped Calix[4]pyrroles

Abstract

LiCl is a classic "hard" ion salt that is present in lithium-rich brines and a key component in end-of-life materials (that is, used lithium-ion batteries). Its isolation and purification from like salts is a recognized challenge with potential strategic and economic implications. Herein, we describe two ditopic calix[4]pyrrole-based ion-pair receptors (2 and 3), that are capable of selectively capturing LiCl. Under solid-liquid extraction conditions, using 2 as the extractant, LiCl could be separated from a NaCl/KCl salt mixture containing as little as 1 % LiCl with circa 100 % selectivity, while receptor 3 achieved similar separations when the LiCl level was as low as 200 ppm. Under liquid-liquid extraction conditions using nitrobenzene as the non-aqueous phase, the extraction preference displayed by 2 is KCl>NaCl>LiCl. In contrast, 3 exhibits high selectivity towards LiCl over NaCl and KCl, with no appreciable extraction being observed for the latter two salts.

Removal of Anions from Aqueous Media by Means of a Thermoresponsive Calix[4]pyrrole Amphiphilic Polymer

“…C4Ps have also been shown to act as extractants for various cesium halide anion salts under conditions of liquid‐liquid extraction . In certain cases, the organic receiving phase could be back extracted with an acidic aqueous solution allowing the system to be recycled . In recent years, considerable progress has been made in the area of CsNO 3 extraction as required for the remediation of radioactive tank waste .…”

“…This, in turn, would provide effective removal of the bound anion from the aqueous medium without the need for contact with an organic solvent. Exposure to dilute acid was then expected to induce release of the bound anions . Dialysis (to remove residual acid and salts) and drying would then give the polymeric material suitable for reuse.…”

Sensing and Liquid–Liquid Extraction of Dicarboxylates Using Dicopper Cryptates

“… 11 − 14 The latter applications have generally involved the extraction and/or transport of halides—chloride in particular—or oxoanions. 15 − 19 Despite the promising features of cage-like systems, their application in these fields is difficult to achieve.…”

The Effect of Substitution Pattern on Binding Ability in Regioisomeric Ion Pair Receptors Based on an Aminobenzoic Platform

“…In contrast, homotopic receptors possess a recognition motif exclusively for a cation or anion, hence they must compete with the counterion for binding of the corresponding ion [10]. The binding of a whole ion pair by ditopic receptor improves the salt’s lipophilicity, thus facilitating its solubilization, extraction, and membrane transport [11,12,13,14,15,16,17,18,19]. For these reasons, such systems are extremely important in the context of biology, environmental protection, and medicine [20,21,22].…”