Ionic transport against its concentration gradient across bipolar membranes

Abstract

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