Fabrication of anti-fouling polyester nanofiltration membrane for dye desalination

Polyester nanofiltration membranes with a loose selective layer are highly promising for separating dyes and salts. In this study, three anti-fouling polyester nanofiltration membranes were prepared by interfacial polymerization of xylitol (E967), xylitol/β-cyclodextrin (E967/β-CD), and xylitol/sodium alginate (E967/SA) with trimesoyl chloride on a polyethersulfone (PES) substrate. The chemical structure, morphology, pore size, hydrophilicity and zeta potential of three polyester membranes were characterized. The preparation conditions, separation performance for dyes and salts, and anti-fouling properties were studied. The results indicated that the addition of β-CD or SA inhibited the esterification reaction, resulting in a thin and loose polyester layer. The polyester layer thicknesses of the PES/E967/β-CD and PES/E967/SA membranes were 92 nm and 79 nm, respectively. In addition, the hydrophilicity and electronegativity of the polyester layer were enhanced. Three polyester membranes all showed a rejection of >99.5 % for Congo red. The permeance of the PES/E967/β-CD membrane was the highest (18.3 L·m−2·h−1·bar−1), whereas the NaCl rejection of the PES/E967/SA membrane was the lowest (9.1 %). Compared with the PES/E967 membrane, the fouled PES/E967/β-CD and PES/E967/SA membranes had longer wash cycles, suggesting an advantage in dye/salt separation.