Electrically Charged Membrane are porous in structure. The pore walls carry fixed ions, which may be positively or negatively charged. In the case of positive ions, the membrane is referred to as an anion-exchange membrane.
With negative fixed ions, it is called a cation-exchange membrane. Separation in an electrically charged membrane is achieved not only by pore size, but also by the exclusion of co-ions from the membrane.
Membranes that consist of a mixture of a negatively and positively charged macroscopic segments are referred to as mosaic membranes.