Inorganic porous membranes for liquid phase separation

Porous ceramic membranes are reviewed with reference to liquid phase separation. Methods for preparing porous ceramic membranes are summarized after a brief introduction to membranes and membrane processes. In the section on liquid phase separation, membrane materials are summarized from the viewpoint of pore size limits, since the pore sizes of porous membranes play an important role in determining separation performance. Various types of metal oxides and composite oxides have been developed by the sol-gel process; typical materials are Al2O3, TiO2, SiO2, ZrO2, and composite oxides. The sol-gel process has a great advantage in terms of pore-size controllability over a wide range, from 0.5 similar to several ten nm, and therefore, is suitable for preparing membranes for use in liquid phase separation. Applications of inorganic membranes are reviewed in terms of water treatment, separation of nonaqueous systems, and photocatalysis.