Pressurizing Distillate Membrane Distillation Assisted by Impedance-Based Liquid Entry Pressure Measurement for Effective Wetting Mitigation

Abstract

Membrane wetting is a prominent challenge in the practical applications of membrane distillation (MD). In this study, we hypothesize that increasing the hydraulic pressure on the distillate side (P_d) can mitigate membrane wetting, an operation mode we refer to as pressurizing distillate membrane distillation (PDMD). To implement PDMD, an accurate measurement of the liquid entry pressure (LEP) of the membrane with the feed solution is essential. However, the conventional LEP measurement method struggles with solutions containing amphiphilic agents. Herein, we develop an impedance-based LEP measurement method and validate it by measuring the LEPs of a commercial poly(tetrafluoroethylene) (PTFE) membrane with ethanol–water mixtures. Further, we demonstrate that this method can accurately measure the LEPs of the PTFE membrane with solutions containing sodium dodecyl sulfate (i.e., a representative amphiphilic agent) by capturing the subtle changes of the feed solutions within the membrane. Additionally, we show that PDMD can effectively mitigate membrane wetting induced by various wetting agents, as the elevated P_d results in a transmembrane hydraulic pressure lower than the LEP of the membrane. Overall, our study provides an effective wetting mitigation approach that can be easily applied in practical MD and membrane contactor applications.