Preparation and characterization of novel chitosan composite nanofiltration membrane containing mesogenic units

Abstract

Conventional nanofiltration (NF) membranes had a relatively low flux. In this paper, two mesogenic compounds were grafted to chitosan in order to change the structure, hence the performance of the NF membrane. A series of novel composite NF membranes were prepared by over-coating the polysulfone ultrafiltration membrane with the mixture of chitosan and mesogenic compounds modified chitosan. The two mesogenic compounds and their chitosan derivatives were characterized by infrared spectrophotometer (IR), differential scanning calorimetry (DSC), polarized optical microscope (POM); the structure of the membrane was characterized by scanning electron microscopy (SEM). The composite NF membrane's rejection rate and flux were strictly related to the mesogenic compound grafted to chitosan and its composition. Extremely high flux, 2543.3lm−2h−1 was observed with P2–4 composite NF membrane, and the rejection remained to be as high as 66.3% at 0.4MPa with 1000mg/L NaCl. These results, together with SEM and infrared images of the composite NF membrane, indicated that the mesogenic compound structure was crucial for the structure and function of the composite membrane.