(465g) Investigation of Protein Adsorption Behavior On Polymer Surfaces Using Atomic Force Microscopy and Quartz Crystal Microbalance with Dissipation

Membrane fouling is the most serious problems in the water treatment with membrane. Previous studies have shown that the hydrophobic interaction between foulants such as proteins and polymeric membranes used for the water treatment causes the serious membrane fouling. However, the mechanism has not been well known. In this study, the fouling behavior, the adsorption behavior and the interaction between protein and polymers were focused on. Bovine serum albumin (BSA) was used as a foulant and polyvinylidene difluoride (PVDF), polyethylene-polyvinyl alcohol copolymer (EVOH) and polyether sulphone (PES) were used as polymers. To grasp the fouling behavior, hollow fiber membranes from these polymers with the similar pore sizes and water permeabilities were prepared through non-solvent induced phase separation (NIPS) method. After that, the filtration and the backwashing experiments were performed with these membranes and BSA. In addition, the adsorption behavior on the polymer surface and the interaction forces between the foulants and the polymers were investigated using quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM), respectively.

First, from the result of the filtration experiment, it was found that both of the permeability decrease and BSA rejection showed the highest values in the case of PVDF and were the lowest in the case of EVOH. In addition, the effect of backwashing was not observed.

From the result of QCM-D experiment, the amount of adsorption becomes higher in the order of PVDF, PES and EVOH. This tendency is the same as the result of the filtration experiment. It was found that BSA adsorbed on any polymer surfaces with a single layer, because the plots correspond with Langmuir isotherm.

In addition, from the result of viscoelastic analysis of adsorption layer obtained from QCM-D, it was found that BSA formed the rigid layer at initial adsorption in the case of PVDF. This is because BSA deforms on the polymer surface by the strong hydrophobic interaction between PVDF and BSA. In contrast, BSA was found to adsorb on both PES and EVOH membrane surface in a soft layer.

Finally, from the result of AFM, it was found that the desorption forces from any polymer surfaces were almost the same. In addition, the desorption forces were much higher compared with the adsorption forces.