Regulating surface-pore structure of PES UF membrane by addition of “active” nano-CaCO3

A small surface-pore ultrafiltration membrane with a high surface porosity was fabricated from a polyether sulfone (PES) dope solution containing a small quantity of CaCO3 nanoparticles (nano-CaCO3), which coagulated in dilute HCl solution. During membrane formation, CO2 nanobubbles were in-situ generated to delay phase inversion, which ameliorated the membrane structure and performance because CO2 nanobubbles are amphiphobic to water and solvent. With increasing nano-CaCO3 content (from 0 to 0.15%) in the dope solution, the surface porosity and the surface-pore density of the obtained PES UF membrane were markedly increased from 1.76 to 6.50% and from 8.31 × 1014 to 5.08 × 1015 m−2, respectively. Nonetheless, the surface-pore size decreased from 13.35 to 8.29 nm, and so as the distribution. The optimal membrane exhibited a high pure water flux (698.2 L·m−2·h−1) and a high rejection to bovine serum album (>99%) with a moderate anti-fouling ability. This work would be of great significance for precision separation in biopharmaceutical, food processing, and other related applications.