IONIC TRANSPORT AGAINST ITS CONCENTRATION GRADIENT ACROSS BIPOLAR MEMBRANES

Countertransport of ions is defined as the transport of an ion against its own concentration gradient driven by the third driving electrolyt e added to the systems. The countertransport was simulated for K+ and Ca2+ ions in dialysis systems that consist of two electrolyte solution s divided by a bipolar membrane as a function of the mobility of the d riving ions, the charge density and thickness of the negative and posi tive components of the membrane. The simulations show that the counter transport occurs in the direction either of or opposite to the concent ration gradient of the driving electrolyte depending on the values of the above parameters and on the bipolar direction, and that the direct ion of the countertransport can alter in a run under certain condition s. The permselectivity of the membrane for ionic valence depends on th e bipolar direction.