A novel N, O-carboxymethyl amphoteric chitosan/ poly(ethersulfone) composite MF membrane and its charged characteristics

An amphoteric chitosan derivative, containing carboxymethyl (–COOH) groups and amine (–NH2) groups, had been prepared. FT-IR spectra confirmed the presence of γsymCOO (1408 cm–1) and γasCOO (1584 cm–1) on the structural units of the chitosan derivative, and 13C NMR spectra revealed that carboxy methylation reactions took place not only on the –OH but also on the –NH2. N, O–carboxymethyl chitosan (CM–CS)/ poly(ethersulfone) (PES) composite microfiltration (MF) membranes were prepared by immersing PES MF membranes into CM–CS solutions and cross-linking with glutaraldehyde. Streaming potential measurements indicate that the CM–CS/PES composite MF membranes possess a weaker positively charged characteristic at low pHs but a stronger negative charged characteristic at high pHs than the chitosan composite membrane (CS/PES). It was further observed that the CM-CS/PES composite membranes have higher adsorption capacities of bovine serum albumin (BSA) than the CS/PES composite membranes and PES membrane at lower pH 3.0– 4.7, and lower adsorption capacities at higher pH 6.0–8.0. Therefore, the CM-CS/PES composite membranes may be suitable for resistant to protein fouling at high pHs or protein adsorption separations at low pHs applications.