Effect of boehmite sol on the performance of alumina microfiltration membranes

Precursor film method was used to prepare highly permeable ceramic microfiltration membranes in this work. The performance of alumina microfiltration membranes was improved by adding boehmite sol in the membrane precursor film. With increasing the boehmite sol content, the effective average pore size of the membrane was continuously decreased and the separation efficiency of the membrane was increased. These improvements were due to that the boehmite sol not only helped the dispersion of the α-Al2O3 powder in the membrane forming slurry, but also formed γ-Al2O3 in the gaps among the existed α-Al2O3 particles which was beneficial for membrane sintering and pore size decreasing. For the membrane prepared with 45 wt% boehmite sol, the effective average filtration pore diameter was 178 nm and the water permeance of the membrane reached 1691 Lm−2h−1bar−1, which was much better than the values reported before. Moreover, the reusability of the membrane was confirmed using a recycling test.