Enhanced permselectivity and resistance of nanofiltration membrane through short hydrophobic chain-based surfactant-regulated interfacial polymerization

Membranes with high selectivity and water permeance are required for improving product water quality and increasing process efficiency. Traditional surfactant-assisted interfacial polymerization (IP) could improve selectivity of polyamide (PA) nanofiltration (NF) membranes but usually decreased water permeance. Here, short hydrophobic chain surfactant, sodium p-styrene sulfonate (SSS) with styrene and sulfonic acid groups was utilized as a new aqueous surfactant during IP process to prepare the PA-NF membrane, improving water permeability and salt rejection simultaneously. SSS had higher critical micelle concentration and can be richly incorporated within PA layer. The membranes characterizations were conducted by atomic force microscopy, scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, goniometer, and zeta potential analyzer. The regulated membrane exhibited slightly enlarged and more uniform pore size, as well as smoother, more hydrophilic and negatively charged membrane surface. The water flux increased from 46.6 ± 3.7 L∙m −2 ∙h −1 to 61.9 ± 2.6 L∙m −2 ∙h −1 (increasing by 32.83%), while Na 2 SO 4 rejection increased by 10.18%. The Cl − /SO 4 2− selectivity increased from 15.2 to 45.1 when using mixed salts solution as feed. Furthermore, SSS-regulated membrane demonstrated increased tetracycline rejection. Enhanced resistance properties (pH stability and antifouling properties) were also observed for SSS-regulated membrane. The study presents a novel surfactant for the fabrication of PA-NF membrane.