Preparation of Asymmetric Alumina Membrane by Sol-Gel Techniques

The clear stable sols were obtained above 50℃ with about 100:1 suitable H2O/Al3+mol ratio,5.1 ROH/H+, 0.07:1 H+/Al3+ concentrations of peptizant acid. Crack-free alumina membranes were obtained by rapid gelation processing of sols in shorten gel time. The suitable concentration of the sol was between 0.5~1.4 mol AlOOH/l sol, the suitable spraying distance shorter than 200mm. The pore size of the membrane was influenced by the size of boehmite grain, the pore size of γ-Al2O3 prepared by the boehmite sol with 3 nm grain size was about 3nm. Asymmetric alumina membrane was obtained by further modifying alumina supporter by using the clear stable sol. When the mean diameter of the colloidal particles was equivalent to the most pore size of the supporter, the crack-free gel film can be stably deposited on the supporter. With 0.1μm of the most pore size as the supporter, the γ-Al2O3 membrane of 3nm pore size was obtained by using the spraying sol of 100nm colloidal particles.