Synergistic interfacial polymerization mediated by in-situ bubbles and surfactant for Mg2+/Li+ separation

Nanofiltration membranes were prepared by regulating monomer diffusion. • Nanofiltration membranes with tailored pore distribution and thinner structure achieved • Nanofiltration membranes exhibit an exceptional Li + /Mg 2+ selectivity of 173. • Nanofiltration membranes exhibit a high water permeance of 15.4 L·m −2 ·h −1 ·bar −1 . Amid the urgent demand for lithium resources driven by the global carbon neutrality goals and the rapid development of the new energy industry, efficiently separating and extracting lithium from salt lakes has emerged as a challenge. Current nanofiltration membranes exhibit issues such as low selectivity, limited permeance, and broad pore size distribution in Li + /Mg 2+ separation. This study proposes a novel strategy for the synergistic control of interfacial polymerization by combining electrically generated in-situ bubbles with surfactants. Electrolysis of water generates negatively charged hydrogen bubbles that attract positively charged amine monomers via electrostatic interaction. Synergized by electric field forces and the buoyancy of the bubbles, the amines are transported to the water/hexane interface for enrichment. Meanwhile, a surfactant added to the oil phase forms a monolayer at the oil-water interface, reducing surface tension and promoting the diffusion of the amine monomers. These mechanisms synergistically modulate interfacial polymerization kinetics, optimizing polyamide density and pore size distribution. The resulting membrane demonstrates an excellent Li + /Mg 2+ selectivity of 173 and high water permeance of 15.4 L·m −2 ·h −1 ·bar −1 . This work presents a novel and feasible strategy that holds promise for achieving large-scale production and advancing the development of efficient lithium extraction technologies from salt lake brine.