Effects of surface crosslinking on sieving characteristics chitosan/poly(acrylonitrile) composite nanofiltration membranes

Effects of surface crosslinking of chitosan/poly(acrylonitrile) (PAN) compo site nanofiltration membranes at different crosslinker (glutaraldehyde) con centrations and crosslinking times on their surface chemical composition an d sieving properties such as pure water permeation, molecular weight cut-of f and the rejection of mono/divalent salts and mono/oligosaccharides were i nvestigated. Fourier transform infrared-attenuated total reflectance spectr oscopy (FTIR-ATRS) and X-ray photoelectron spectroscopy (XPS) studies revea led the crosslinking of chitosan with glutaraldehyde as well as variations in chemical composition with glutaraldehyde concentration and crosslinking time. Pure water permeation/swelling in water decreased and rejection of sa lts and sugars increased with increasing glutaraldehyde concentration, indi cating pore contraction and increase in hydrophobicity as well as pore tort uosity due to crosslinking. Molecular weight cut-offs of surface crosslinke d membranes were in the range of 550-700 Da. a characteristic of nanofiltra tion membranes, whereas uncrosslinked membrane had cut-off of > 1500 Da. Th e crosslinked membranes were found to be stable over 10-h operation for pur e water permeation and the stability increased with increasing glutaraldehy de concentration. (C) 2000 Published by Elsevier Science B.V.