Permeability and selectivity analysis for ultrafiltration membranes

One of the major challenges facing end-users of ultrafiltration membranes is the difficulty in comparing membrane products provided by different manufacturers and made from different polymeric or ceramic materials. In this short communication, we examine the trade-off between permeability and selectivity for different ultrafiltration membranes using data for bovine serum albumin. Results for a number of different ultrafiltration membranes fall along, or below, an upper bound that reflects the current state-of-the-art in commercial ultrafiltration membranes, analogous to the Robeson Plot used to analyze the performance of gas separation membranes. The shape of this upper bound is consistent with a theoretical analysis of solute and solvent transport through a membrane composed of a parallel array of cylindrical pores having a log-normal pore size distribution. These results provide a framework that can be used to analyze the performance of new ultrafiltration membranes, an approach that was demonstrated using data for a prototype negatively charged ultrafiltration membrane. (C) 2004 Elsevier B.V. All rights reserved.