Solvent and pH resistance of surface crosslinked chitosan/poly(acrylonitrile) composite nanofiltration membranes

The resistance of novel surface crosslinked Chitosan/poly(acrylonitrile) (P AN) composite nanofiltration (NF) membranes to pH and organic solvents was studied with respect to the effects of crosslinking parameters, namely, glu taraldehyde concentration and crosslinking time. The pH resistance was dete rmined by permeation of aqueous acidic (pH 2.5) and basic (pH 11) solutions as well as swelling studies in the pH range of 2.5-11. The solvent resista nce was determined by swelling, immersion, and permeation studies with seve ral industrially important organic solvents, namely methanol, ethanol, iso- propanol, methyl ethyl ketone, ethyl acetate and hexane. It was observed th at the crosslinked composite membranes maintain the permeate fluxes for tes t solvents for 2 h of continuous operation without any significant change i n flux. SEM studies on membrane samples after immersion as well as permeati on with the above-mentioned solvents indicated that the membrane morphology was maintained. The results are explained in terms of solvent-membrane pol ar and hydrophobic interactions, using solubility parameters of membrane an d solvents and dielectric constants of solvents. Pure water flux and polyet hylene glycol transmission data indicated that at pH 2.5 and 11, the membra ne stability increased with increasing glutaraldehyde concentration and was much better at pH 11 than at pH 2.5. All surface crosslinkcd membranes sho wed reduced swelling between pH 4-10. (C) 2000 John Wiley & Sans, Inc.