PEI-Reinforced GO/g-C₃N₄ Composite Membrane for Salt Separation

Membrane separation is an important separation and purification technology, membrane materials are the key to membrane separation technology, and the rapid development of two-dimensional materials in recent years has brought new opportunities for membrane separation technology. Graphene oxide (GO) is a hydrophilic two-dimensional material, and its unique physical and chemical structure and properties give it the potential to become a high-performance separation membrane; however, the instability limits its application. In this study, a two-dimensional material, graphite-phase carbon nitride (g-C₃N₄), was integrated into graphene oxide (GO) to address the challenges associated with its practical applications. This modification not only endows the material with more advantageous properties as a membrane but also introduces a heterogeneous structure that bolsters the composite membrane's stability. This structure also enhances the permeability and selectivity of the membrane, leading to impressive results in self-driven permeation tests and staggered-flow filtration tests under applied pressure. Following additional surface charge modifications, the composite membrane demonstrated a separation efficiency of approximately 90.4% in permeation tests and an impressive separation efficiency of 63.8% in filtration tests for binary mixed salt solutions. These results indicate a significant capability for mono- and divalent ion separation, suggesting promising potential for salt separation applications.