Evaluating the role of interfacial phenomena on ion transport in SLM biomimetic systems

Abstract

Supported Liquid Membrane (SLM) systems have previously been shown to be an effective mimic of the active transport process for ionic species. Unfortunately, unexplained order-of-magnitude differences in the flux of similar ions, such as copper and nickel, were observed. This study challenges the prior assumption that interfacial phenomena were insignificant in determining the controlling mechanism for transport. Preliminary data indicate that the desolvation rate and equilibrium partitioning between the aqueous and organic phases can play a dominate role for select ions. Dynamic approach to equilibrium experiments were conducted on batch copper and nickel systems. Each system exhibited a time constant of approximately 0.1 hr. which invalidates the prior assumption of instantaneous establishment of interfacial equilibrium. It does, however, explain the observed lag time in establishing the steady state profiles in the SLM systems. Furthermore, the final interfacial concentrations of copper are an order of magnitude greater than that for nickel, consistent with prior observations on flux differentials. These high interfacial copper concentration do validate that the controlling resistance for copper systems is within the SLM itself. However it is clearly species dependent as illustrated by the nickel system.