A new solvent extraction technology and mechanism for the separation and recovery of Li+ using benzene sulfonamide acid substance

Lithium and its compounds are important strategic resources for the economy and national defense construction. In the Chinese lithium industry, Qinghai old brine, which is the main source of Li + , contains Mg 2+ as much as 125.6743 g/L, and the effective separation of these two elements has been a challenging task. We designed and synthesized a benzene sulfonamide acid substance N221 with stronger acidity and steric hindrance to effectively extract Li + in high Mg/Li solution. The existing acidic extractants include P204, P507 and Cyanex272, among which N221 has the highest β Li/Mg value and E Li (%) value. The thermodynamic properties of the reaction between N221 and metal ions was explored by means of thermodynamic equilibrium constant and quantum chemical calculation. A large amount of Mg 2+ in salt-lake promoted the extraction of Li + , and the mechanism was revealed by mean of molecular dynamics simulations. After stripping, the final Mg/Li (mol/mol) decreased from 15.80 in the Qinghai old brine to 1.27, which meets the conditions of further refining and can obtain high-purity lithium products. A process for separating Li + from Mg 2+ by benzene sulfonamide acid substance is proposed in this study, and the reasons are explained in depth from the experiments and molecular dynamics simulations. Hence, it can be foreseen that this study also has broad application prospects in the recovery of lithium from spent lithium-ion batteries containing a variety of high-valence metal ions.