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

Abstract

To obtain γ-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 γ-Al2O3 products. In this work, mesoporous γ-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 γ-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 γ-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 γ-Al2O3 ultrafiltration membranes derived from the pseudo-boehmite exhibited a relatively high permeability (＞94.5 L m−2 h−1⋅MPa−1), which was higher than that of the aluminum alkoxide derived.