Surface modification is a promising method to improve polymeric membrane's pervaporation performance. In this paper, the surface carboxylation of glutaraldehyde crosslinked chitosan (CS-GA) membrane was successfully achieved by the reaction of amine groups on the CS-GA membrane surface with anhydride groups of maleic anhydride (MA) in acetone solution. The resulting membrane was characterized by attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The pervaporation performance of MA surface-modified CS-GA membrane (CS-GA-MA) for the separation of various organic/water mixtures was investigated. The results showed that both the flux and the separation factor were enhanced as CS-GA membrane was treated by MA. For the separation of 90 wt% ethanol/water mixture at 60 degrees C, the separation factor and the flux of the CS-GA-MA membrane were 634 and 300 g/m(2) h, respectively. However, the separation factor and the flux of the un-modified CS-GA membrane was 105 and 250g/m(2) h. Meanwhile, the flux increased greatly and the water concentration in the permeate decreased slightly (by about 0.7%) as the operating temperature increased from 30 to 60 degrees C. Similar results were observed when the modified membrane was employed to separate various aqueous organic solutions. These data indicated that the surface carboxylation was a very effective method to improve pervaporation performance of CS-GA membrane for the separation of aqueous organic mixtures. (C) 2007 Elsevier B.V. All rights reserved.