Fabrication of polyphenylsulfone/polyetherimide blend membranes for ultrafiltration applications: The effects of blending ratio on membrane properties and humic acid removal performance

In this study, a blending technique was employed to prepare an antifouling ultrafiltration membrane for humic acid (HA) separation. Using a nonsolvent induced phase separation method, negatively charged/hydrophobic polyphenylsulfone (PPSU) was blended with positively charged/hydrophilic polyetherimide (PEI) to form PPSU/PEI blend membranes. Depending on the blending ratio, the membrane surface properties, such as morphology, hydrophilicity, roughness, and surface charge, were tailored to improve the resistance of the membrane to fouling. For example, the blend membranes possessed a weak negative charge and exhibited good resistance to the negatively charged HA due to the effect of electrostatic repulsion. As the PEI content increased, the hydrophilic PEI segregated to the membrane/water interfaces, creating a hydrophilic surface and changing the surface charge from negative to neutral.