Effect of protein on PVDF ultrafiltration membrane fouling behavior under different pH conditions： interface adhesion force and XDLVO theory analysis

To further detem3ine the fouling behavior of bovine serum albumin （BSA） on different hydrophilic PVDF ultrafiltration （UF） membranes over a range of pH values, self-made atomic force microscopy （AFM） colloidal probes were used to detect the adhesion forces of membrane-BSA and BSA BSA, respectively. Results showed that the membrane-BSA adhesion interaction was stronger than the BSA-BSA adhesion interaction, and the adhesion force between BSA-BSA-fouled PVDF/PVA membranes was similar to that between BSA-BSA-fouled PVDF/PVP membranes, which indicated that the fouling was mainly caused by the adhesion interaction between membrane and BSA. At the same pH condition, the PVDF/PVA membrane-BSA adhesion force was smaller than that of PVDF/ PVP membrane-BSA, which illustrated that the more hydrophilic the membrane was, the better antifouling ability it had. The extended Derjaguin-Landau-Verwey Overbeek （XDLVO） theory predicts that the polar or Lewis acid-base （AB） interaction played a dominant role in the interracial free energy ofmcmbrane-BSA and BSA BSA that can be affected by pH. For the same membrane, the pH values of a BSA solution can have a significant impact on the process of membrane fouling by changing the AB component of free energy.