Variable—pore-size membrane is a new kind of selective separaation membrane. The separation mechanism of this kind of membraoe is different from that of the other ordinary membrane processes now used. In the separation process

the pore size or permeation channel of this kind of membrane isdependent on the operation condtion(such as pH value

formation of complex

applying electric field

etc.)and can be controlled so that mixture feed can be separated selectively. In this paper

the principle of the membrane pore size variation

Selection of the membrane material

device of the membrane structure and the application of this kind of membrane have been introduced.