NET PENETRATION CHARGES OF AN ION-PENETRABLE MEMBRANE IN A GENERAL ELECTROLYTE SOLUTION

An analytical expression is derived for the net amount of charges pene trating into a membrane, which is immersed in an electrolyte solution. The membrane carries fixed charges due to, for example, the dissociat ion of the functional groups it carries. Planar, cylindrical, and sphe rical membranes and a general electrolyte solution are considered. The estimation of the amount of penetration charges is essential to the d escription of membrane properties. We show that the amount of fixed ch arges and the potential gradient at the membrane-liquid interface are two key factors to determine the net amount of charges penetrating int o a membrane. The deviation of the present approximate result from the corresponding exact value, which needs to be evaluated numerically, i s on the order of 5%. (C) 1995 Academic Press, Inc.