Polyelectrolyte-based antifouling and pH-responsive multilayer coatings for reverse osmosis membrane

Abstract

Membrane fouling, the accumulation of material on the membrane surface, has been a challenge that limits the application of reverse osmosis technology. Ordinary cleaning processes do not remove contaminants from the membrane surface. To effectively clean a membrane, we fabricated a sacrificial multilayer polyelectrolyte coating based on a layer-by-layer assembly approach using chitosan (CS) and tannic acid (TA) on the membrane surface. The CS/TA coated membranes represent a superior permeance flux of 64 L m⁻² h⁻¹ with a clear NaCl rejection of 98.89 %. Meanwhile, the membrane surface hydrophilicity was enhanced due to the abundant amino and hydroxyl groups, which shows superior anti-fouling properties against proteins, polysaccharides, and surfactant. Moreover, the coatings were unstable, which would decompose at pH 8.5. The degradation endows the coated membranes approving long-term anti-fouling performance, which the permeance recovery reaching up to 85 %. Constructing pH-responsive smart coatings provides a promising route to address membrane fouling. It can be upscaled in numerous practical applications like sensors, medical devices, and drug delivery.