Fabrication of Bioinspired Gallic Acid-Grafted Chitosan/Polysulfone Composite Membranes for Dye Removal via Nanofiltration

In this work, we have developed a novel and facile method to prepare gallic acid-grafted chitosan/polysulfone (PS) composite membranes for dye removal from aqueous solutions. First, the gallic acid was grafted onto the eco-friendly chitosan through a free-radical grafting copolymerization reaction. Second, the gallic acid-grafted chitosan conjugates were codeposited onto the top surface of PS substrates by electrostatic interactions in order to transform the ultrafiltration membrane to the thin and defect-free nanofiltration membrane. The morphology and chemical composition of the as-prepared composite membranes were fully characterized by various spectroscopy and microscopy techniques. Moreover, after the optimization of preparation parameters, the obtained membrane displayed a high rejection of 97.2% for Congo red with a high permeance of 14.0 L h–1 m–2 bar–1. Furthermore, the composite membranes also exhibited good rejections for other dyes with different molecular weights such as Evan blue (97.3%), Acid red 94 (97.6%), and Alcian blue 8GX (98%) on the basis of size exclusion, accompanied with good permeance of 12.9, 11.9, and 10.9 L h–1 m–2 bar–1, respectively, which shows potential for scale-up industrial applications.