Preparation of PPS/ZrP/PTFE composite membrane and its performance in lithium-magnesium separation

Efficient extraction of lithium from salt lake brines is critical to alleviating the global lithium resource shortage. In this study, a novel composite membrane was fabricated based on polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), and zirconium hydrogen phosphate (ZrP) for selective lithium-magnesium separation via electrodialysis. The highly crystalline PPS matrix provided a compact and ordered polymer framework, contributing to selective ion transport by creating size-sieving channels that favor the passage of smaller Li⁺ over hydrated Mg²⁺. Meanwhile, the incorporated layered ZrP significantly enhanced the membrane’s hydrophilicity and offered additional pathways for facilitated lithium-ion conduction. Results demonstrated that the composite membrane exhibited remarkable stability during a prolonged 408-hour electrodialysis operation. The Li⁺/Mg²⁺ molar ratio in the cathode chamber increased dramatically from 0.08 to 2.62, representing an approximately 33-fold improvement in separation efficiency. Structural characterization confirmed the formation of high-purity magnesium hydroxide precipitate in the cathode chamber, validating the membrane’s high selectivity and stability. This study provides new insights into the design of high-performance ion-selective membranes for lithium resource recovery.