Facile surface modification of cation exchange membranes via Debus-Radziszewski in-situ cross-linking for lithium extraction from salt-lakes

Abstract

Lithium extraction from salt-lakes is a crucial way to solve the global shortage of lithium resources. With high sustainability and efficient ion separation, electrodialysis (ED) has a high potential for lithium extraction from salt-lakes, yet suffering from the challenges of cation-cation selectivity. In this work, a facile Debus-Radziszewski in-situ cross-linking approach was proposed to construct a polyethyleneimine modification layer containing imidazole groups (PEI-Im) on a common cation exchange membrane (commercial membrane, i.e., CTG membrane) surface to enhance the lithium selectivity. The pore size, architecture rigidity and charged characteristic of this PEI-Im layer were controlled via adjusting the reaction conditions. The resultant membrane (PEI-Im-CTG) exhibited high Li+ permeation rate (0.89 mol·m−2·h−1) and excellent Li+/Mg2+ permselectivity (13.1), which are 4.0 times and 19.8 times higher than that of the pristine CTG membrane, respectively. Moreover, the PEI-Im-CTG membrane based two-stage ED process showed a high Li+ purity (∼99.90 %) and low energy consumption (∼0.158 kWh·mol-1Li+) for Li+ extraction from simulated salt-lakes. This work offers a facile and effective strategy for membrane modification with high Li+ selectivity, which is promising in lithium extraction from salt-lakes.