Abstract

Membrane fouling has always been a huge obstacle to the development of membrane separation technology, including forward osmosis (FO) technology. In this work, polyamide (PA) thin-film composite (TFC) membranes were simply immersed in aluminosilicate nanotubes (ANTs) dispersions to obtain thin-film nanocomposite (TFN) FO membranes. With the help of the opposite surface charge of ANTs and PA layer, and the representative “peak-valley” structure of PA TFC membrane, ANTs are stably bound to the surface of TFC membrane by electrostatic adsorption and physical confinement. The TFN membrane has greatly enhanced hydration ability due to the rich hydrophilic hydroxyl groups of ANTs, “like-zwitterionic” surface composition and rough nanostructure morphology, resulting in good underwater superoleophobicity. Combined with the water transport channel formed by its nanoporous structure, the surface anti-protein adhesion and anti-oil–water emulsion adhesion can be achieved without affecting the water flux. It is worth noting that the surface potential of TFN membrane is close to neutral due to charge neutralization. This avoids the electrostatic interaction between the membrane surface and the contaminant, and further achieves a universal anti-fouling ability that is not affected by protein or emulsion charge, and the irreversible adsorption is close to zero. In addition, the rigid ANTs coating exhibits excellent stability and reusability under long-term use, and the water flux after cleaning can be restored to nearly 99.9%. In general, this method of using ANTs deposition to improve the antifouling performance of PA based TFC membrane is simple, efficient, stable, and easy scalable. This method is not only limited to FO membrane, but also can be extended to PA based reverse osmosis and nanofiltration membranes, which has great practical application potential.

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