Magnetically Ultrastabilized Graphene Oxide-Based Membrane Filter for Point-of-Use Water Treatment

Instability of a graphene oxide (GO) membrane caused by water-induced effects (e.g., swelling) and poor interfacial adhesion to a substrate has largely limited its separation performance and long-term applications (e.g., potential GO leakage risks). To address this issue, here we report, as a proof-of-concept, a magnetically ultrastabilized GO-based membrane filter, unlike conventional approaches such as chemical cross-linking. The GO nanosheets decorated with in situ formed Fe3O4 nanoparticles are first assembled into a membrane filter via vacuum filtration. The filter is subsequently placed in a magnetic field (<= 0.50 T) created by a permanent magnet and tuned by a customized porous support embedded with magnetizable microparticles. The GO-Fe3O4 (GOF) membrane filter remains intact under harsh ultrasonic destabilization (>= 20 min duration, 144 W power, 45 kHz frequency) and turbulent hydrodynamic conditions (e.g., crossflow velocity 30 cm/s for at least 7 days), without any deterioration of permeation or rejection performance. Our experimental and theoretical studies highlight the indispensable role of the magnetizable support in achieving such ultrastabilization, which increases the magnetic flux density gradient and thus the magnetic force by almost 1 order of magnitude. The GOF membrane filter not only has a separation performance comparable to commercial ultrafiltration membranes, but also enables effective inactivation of waterborne pathogens (e.g., E. coli). This simple strategy that magnetically stabilizes functional engineered nanomaterials on a substrate surface opens up new opportunities for developing nanoenabled filters, with minimized leakage and health risks, for point-of-use water purification.