A novel kind of thin film composite nanofiltration membrane with sulfated chitosan as the active layer material

Nanofiltration (NF) has been used as pretreatment to reverse osmosis (RO) desalination processes for lowering the required pressure. In this work, a novel kind of amphoteric thin-film composite (TFC) NF membranes were prepared through a method of coating and cross-linking using sulfated chitosan (SCS), polysulfone (PS) ultrafiltration (UF) membrane, and epichlorohydrin (ECH) as the active layer material, the base membrane, and the cross-linking agent, respectively. At 0.40MPa and ambient temperature, the rejections of the resultant membrane to Na₂SO₄ and NaCl solutions (1000mgL^-1) were 90.8% and 32.5%, while the permeate fluxes were 22.9 and 58.4kgm^-2h^-1, respectively. The structure and morphology of the resultant SCS/PS composite NF membranes were characterized with attenuated total reflection infrared spectroscopy (ATR-IR), environmental scanning electron microscopy (ESEM), and atomic force microscopy (AFM). The rejection performances suggested that SCS/PS composite NF membranes cross-linked by ECH have a potential for the separation of mono/divalent inorganic electrolytes from low-molecular-weight organics.