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 γ_symCOO (1408 cm^-1) and γ_asCOO (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.