High flux zwitterionic hybrid cellulose acetate desalination membranes: Formation of permeability-effective macropores by self-organizing zwitterionic silanes

Abstract

Zwitterionic hybrid cellulose acetate membranes with improved flux and antifouling performance were produced by a modified non-solvent induced phase separation (NIPS) process in which a zwitterionic trimethoxysilane compound, (3-sulfopropylbetaine-propyl)-trimethoxysilane (SPPT), was added to the casting solutions at 1.0, 2.0, and 3.0 wt%. The successful incorporation of SPPT into cellulose acetate (CA) membranes was proved by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and thermal gravimetric analysis (TGA). Permeate fluxes of the hybrid membranes increased significantly compared to the control cellulose acetate membrane prepared without the addition of SPPT (15 bar pressure; 2000 ppm NaCl or MgSO4 aqueous solution filtration). The hybrid membranes exhibited an increase in permeate flux up to 87 % while their salt rejections slightly decreased in NaCl solution filtration. In MgSO4 solution filtration, the flux was increased by 61 % without sacrificing salt rejection. The reason for the enhancement in the flux was the formation of macropores in the membrane bulk structures by self-organizing zwitterionic silane groups. The highest resistance to bovine serum albumin (BSA) or xanthan gum as a foulant was observed in the hybrid membranes produced with 1.0 wt% of SPPT.