Abstract: Different α-Al₂O₃ micro-powders with grain size of 0.5--3μm were coated on α-Al₂O₃substrate by the dipping process, and microfiltration membranes with different pore sizes were prepared. The thickness of all the membranes was controlled to be about 25μm. Then the membranes were modified by nano zinc oxide coating deposited by coprecipitation process with zinc nitrate and urea as starting materials. The influences of the size of α-alumina micro-powders for preparing the membranes and the concentration of zinc nitrate in the precursor of the zinc oxide coating on the water flux of the modified filtration membranes were studied. The results show that the flux of the modified membranes is increased and the amplitude of the flux increasing reaches maximum for the membrane which is made of α-alumina micro-powers with size of 0.5μm. When the concentration of zinc nitrate is 0.3mol/L, the twice coated membrane possessed the best modification effect and the amplitude of the flux increase reaches 46.4%. Furthermore, the mechanism of zinc oxide modification is discussed initially.

Key words: α-alumina microfiltration membrane, different pore size, zinc oxide, modification