Modification of PVDF membrane by chitosan solution for reducing protein fouling

This work studied modification of hydrophobic membrane by chitosan solution for the purpose of reducing protein fouling. The membrane used was flatsheet polyvinylidenefluoride (PVDF) of 0.22 μm pore size. The membranes were modified by 3 different methods, i.e. immersion method, flow through method and the combined flow through and surface flow method. Chitosan solution concentration and modification time were varied. The modified membranes were then neutralized with NaOH solution. The results of scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) study of modified membranes compared to unmodified membranes confirmed that there was chitosan coated on the membrane surfaces. The water contact angles and water fluxes decreased with increasing chitosan concentration and modification time. The result also indicated that modified membranes had higher hydrophilicity than unmodified membrane. In protein fouling experiment, bovine serum albumin (BSA) was used as a protein model solution. Modified membranes exhibited good anti-fouling properties in reducing the irreversible membrane fouling. The membrane modified by a combined flow through and surface flow method showed the best anti-fouling properties compared with other methods. Protein adsorption on the modified membrane was highest at the isoelectric point (IEP) of BSA solution and decreased as the solution pH was far from the IEP.