Simple model for semipermeable membrane:: Donnan equilibrium

We study a model for macroions in an electrolyte solution, confined by a semipermeable membrane. The membrane finite thickness is considered, and both membrane surfaces are uniformly charged. The model explicitly includes electrostatic and size particles correlations. Our study is focused on the adsorption of macroions on the membrane surface and on the osmotic pressure. The theoretical prediction for the osmotic pressure shows a good agreement with experimental results.