Li+ Separation from Multi-Ionic Mixtures by Nanofiltration Membranes: Experiments and Modeling

Abstract

Aqueous sources like salt lake brines and seawater are the most abundant source for lithium ions and might contribute to the growing demand for lithium for energy storage. By coupling with the increasingly relevant reverse osmosis systems, nanofiltration can provide a promising process alternative to conventional methods such as water evaporation and salt precipitation from ores or brines for this purpose. One possible model for nanofiltration is the solution-diffusion-electromigration model (SDEM). First, the model was parametrized by determining the permeances from simple electrolyte mixtures containing two salts. Then, the SDEM was used to predict the rejections of complex multi-electrolyte solutions that mimic seawater and reverse osmosis brine, without fitting additional parameters to experimental data of this complex mixture. This allowed predicting ion rejections satisfactorily. Negative rejections due to spontaneously generated electric fields in the membrane could also be qualitatively described. In summary, this SDEM modeling can provide an important contribution to the purification of Li+ from aqueous sources.

Li+ Extraction from Aqueous Medium Using Tetracyanoborate Ionic Liquids─Experiments and ePC-SAFT Modeling

“…6 Among the various techniques thoroughly investigated, collectively referred to as direct lithium extraction (DLE), are adsorption, 7 precipitation, 8 and membrane separation. 9,10 Further, solvent extraction is promising due to the advantages of continuous operation, slow energy consumption, and noncomplex apparatus. 11,12 An extraction agent is required, and many different chemical systems have been suggested to efficiently extract Li + from aqueous media, such as the tributyl phosphate (TBP)−FeCl 3 extraction agent mixture.…”

“…Among the various techniques thoroughly investigated, collectively referred to as direct lithium extraction (DLE), are adsorption, precipitation, and membrane separation. , Further, solvent extraction is promising due to the advantages of continuous operation, slow energy consumption, and noncomplex apparatus. , An extraction agent is required, and many different chemical systems have been suggested to efficiently extract Li + from aqueous media, such as the tributyl phosphate (TBP)–FeCl 3 extraction agent mixture. , While it offers high extraction efficiency, a third phase might occur during the extraction, and a strongly acidic environment is required for re-extraction . This necessitates specialized equipment and large quantities of base to neutralize the organic phase .…”