We have studied experimentally the effects that the charge adsorbed on
the membrane pore walls exerts on the convective diffusion through a
porous membrane. The plot of the logarithm of the bulk concentration r
atio vs convective flow through the membrane is usually employed to de
termine the membrane parameter A/L (effective membrane area/membrane t
hickness). It is shown that the deviations from the linear behavior of
this plot give us information on the adsorbed charge concentration. A
simple model based on the Nernst-Planck equation for the ion fluxes a
nd the Navier-Stokes equation for the pore fluid velocity has proved t
o be useful for the understanding of the experimental trends observed
over a range of membrane pore radius and electrolyte concentration. Ou
r study can be seen as an independent confirmation of a rather general
result: ion adsorption to the pore walls of inert, porous membranes c
an significantly affect the transport phenomena, especially in the lim
it of low electrolyte concentration.