Preparation of high permeability -Al₂O₃ ultrafiltration membranes from pseudo-boehmite industrial precursor

To obtain gamma-Al2O3 ultrafiltration membranes, AlOOH sols which were usually derived from aluminum alkoxide were used as the top layer precursor. However, the colloidal sols obtained by this process were complex, high cost and time-consuming. Pseudo-boehmite, an industrial product with characteristics of high purity, excellent gelation and strong caking property, was widely used to prepare gamma-Al2O3 products. In this work, mesoporous gamma-Al2O3 ultrafiltration membranes were prepared conveniently and quickly by using pseudo-boehmite powder as precursor with colloidal sol-gel route at room temperature. The effects of H+/Al3+ molar ratio and polyvinyl alcohol (PVA) content on the properties of AlOOH sols and gamma-Al2O3 ultrafiltration membranes were analyzed. Results showed that the viscosity and hydrodynamic particle diameter of the AlOOH sols can be controlled by changing the H+/Al3+ molar ratio, and the pore size of the prepared gamma-Al2O3 ultrafiltration membranes could be varied by adjusting the PVA content in the AlOOH sols coating slurry. The pore size increased from 6.98 nm to 11.34 nm by increasing PVA content from 1.25% to 1.50%. Additionally, the gamma-Al2O3 ultrafiltration membranes derived from the pseudo-boehmite exhibited a relatively high permeability (>94.5 L m(- 2) h(- 1)center dot MPa- 1), which was higher than that of the aluminum alkoxide derived.