A macropurous amphoteric membrane was successfully prepared by solution blending of a natural polymer chitosan (CS) and its derivative carboxymethylchitosan (CMCS). The adsorption of two model proteins (ovalbumin and lysozyme) with very different pH, values on this CS/CMCS blend membrane was investigated in batch systems. The results showed that both proteins could be effectively adsorbed on the membrane, but the adsorption capacities were influenced by the pH, the initial protein concentration and the CMCS content in the membrane. Because of the amphoteric nature of the protein and the CS/CMCS membrane, the pH for the maximum adsorption of ovalbumin and lysozyme was different, which is the basis for the separation of these proteins from binary mixtures. As the CS/CMCS blend membrane also showed good desorption properties for those two proteins, both ovalbumin and lysozyme were successfully separated from binary mixtures by adjusting only the pH of the feed and the desorption solutions. (c) 2009 Elsevier Ltd. All rights reserved.