Preparation and characterization of sulfated carboxymethyl cellulose nanofiltration membranes with improved water permeability

Sulfated carboxymethyl cellulose (SCMC) with tailored amount of sulfate groups was synthesized, and their composite nanofiltration membranes (SNFMs) were prepared by solution casting onto polysulfone (PSF) supporting membrane and crosslinking by glutaradehyde (GA). Chemical structure and composition of SCMCs and SNFMs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. SNFM surfaces were examined by field emission scanning electron microscopy, water contact angle and streaming potential measurement. The effects of the chemical composition on the hydrophilicity, the surface charge and the nanofiltration performance of SNFMs were determined. It is found that the incorporation of sulfate groups improves the water permeability of SNFMs while retaining their salt rejection. For the feed mixture of aqueous Na2SO4 (1.0 g L− 1, pH = 6.5), the optimum water flux is 39.6 L m− 2 h− 1, which is 2.2 times of the pristine SNFM-0. For the xylenol orange (XO) dye solution (0.1 g L− 1, pH = 4.0), the flux of SNFM-3 (30.0 L m− 2 h− 1) is also higher than that of SNFM-0 (11.1 L m− 2 h− 1). In addition, SNFM-3 exhibits good separation performance and chemical stability in treating saline anionic dye aqueous solution (MYB/NaCl) in acidic conditions.