A Diafiltration Apparatus for High-Throughput Characterization of Transport Through Polymer Membranes*

Creating systems and techniques capable of reducing the time and resources needed to characterize the transport properties of membranes can help to increase the rate of material and process development. In this study, a diafiltration apparatus is developed to rapidly characterizing membrane performance over a broad range of feed solution compositions. The apparatus doses a fixed-concentration diafiltrate solution into a stirred cell to achieve a predetermined change in the retentate concentration. Here, it was shown that membrane performance, within a 1 to 100 mM KCl phase space, could be probed ten times more quickly with one diafiltration experiment (4 h) than with a traditional experimental campaign (47 h). The synergy between data analytics and instrumentation led to the incorporation of inline conductivity probes that monitored the real-time permeate and retentate concentrations. This additional information provided key insights to distinguish between the mechanisms that govern membrane separations (e.g., discriminating between adsorption or rejection-based separations) and allowed for the membrane transport coefficients to be determined accurately. Ultimately, the ability of this device to characterize membranes rapidly will help to address knowledge gaps related to the interfacial processes that govern solute–solute selectivity and the performance of membranes in complex multi-component feed streams.