Prediction of pervaporation performance of aqueous ethanol solutions by nanopermporometry characterization

This study proposes a new method, nanopermporometry with simultaneous measurement of vapor (NPPV), for prediction of the performance of pervaporation (PV) dehydration of aqueous ethanol solutions. In conventional nanopermporometry (NPP), only the permeate flux of a non-condensable gas such as air is measured as a function of humidity, and the pore size distribution is obtained based on blocking the permeation of a non-condensable gas (air) using a capillary-condensed vapor. With NPPV the permeate flux of both water and air are measured simultaneously. PV measurements of the feed ethanol at a concentration of 94 wt% were carried out at 70 °C after the corresponding NPPV measurement. Both the separation factor and the water flux showed time-dependence before reaching a steady state after several hours. A separation factor of 132 and a water flux of 0.52 kg/(m2 h) were obtained using sol–gel-derived silica membranes. The NPPV fluxes of water and air at relative humidities of 2, 13 and 60% were used to predict PV performance, i.e., the separation factor and flux. The NPPV air flux at 13% RH (Kelvin diameter: 1 nm) was correlated with PV ethanol flux, and NPPV water flux at 13% RH was correlated with PV water flux. Moreover, the ratio of NPPV water flux to air flux at 13% RH was correlated with the PV separation factor.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ NPPV with measured condensed vapor was used to predict PV performance. ▶ α (1 3 2) and water flux (0.52 kg/(m2 h)) showed time course before steady state. ▶ NPPV air flux decreased, water increased at 0–60% RH. Both permeance decreased.▶ Air and water flux at 13% RH in NPPV was correlated with PV ethanol and water flux.▶ NPPV ratio of water flux to air flux at 13% RH was correlated with PV α.