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.

Effect of electrokinetic property membrane on bovine serum of charged polyether sulfone albumin fouling behavior

Negatively charged carboxymethylated polyethersulfone （CMPES） and positively charged quater- nized polyethersulfone （QAPES） ultrafiltration （UF） membranes were prepared by bulk chemical modification and non-solvent induced phase separation method. The effects of PES membrane interracial electrokinetic property on the bovine serum albumin （BSA） membrane fouling behavior were studied with the aid of the membrane-modified colloidal atomic force microscopy （AFM） probe. Electrokinetic test results indicated that the streaming potential （AE） of QAPES membrane was not consistent with its expected 1EC value, however, within the pH range of 3-10, the ζpotentials of two charged-modified PES membranes were more stable than the unmodified membrane. When pH value was 3, 4.7 or 9, the interaction behavior between charged PES membrane and BSA showed that there was significant linear correlation between the jump distance ro ofmembrane-BSA adhesion force （F/R） and the ~＂ potential absolute value. Charged modification significantly reduced the adhesion of PES membrane-BSA, and the adhesion data was good linear correlated with the flux decline rate in BSA filtration process, especially reflected in the CMPES membrane. The above experimental facts proved that the charged membrane interracial electric double layer structure and its electrokinetic property had strong ties with the protein membrane fouling behavior.