A novel positively charged membrane based on polyamide thin-film composite made bycross-linking for nanofiltration

Abstract

In this paper, a novel positively charged membrane was prepared through interfacial polymerization technique between poly ethylene imine in aqueous phase and trimesoyl chloride in organic phase. Next, cross linking of polyamide (PA) layer using ?-xylylene dichloride (XDC) and glutaraldehyde (GA) was studied. The influences of cross-linking concentrations on the separation and permeation Performance of membrane were also investigated. Membranes were characterized in terms of their chemical structure, the cross-sectional and surface morphologies, contact angles, molecular weight cut-off (MWCO) and effect of pH feed solution. The salt rejection sequence of CaCl2>NaCl>Na2SO4 showed a positive charge at the membrane surface after cross-linking reaction. The MWCO of primary PA membrane decreased from 1,135 to 775 and 885 Da for XDC and GA, respectively. XDC membrane shows highest CaCl2 divalent cationic rejection (95.5%) and lowest water flux (21.1L/m .h). This study illustrates a promising method for fabrication of positively charged membrane in cation separation.