Vial-based screening method for assessing pervaporation performance of flat sheet membrane samples

Abstract

A vial-based method for generating screening-level pervaporation performance information for flat membrane samples, with a significantly higher sample throughput than conventional bench-scale tests, was proposed and evaluated using water/ethanol mixtures. The flux of a compound through the membrane, installed as the exposed septum of the vial, is governed by membrane permeance and the partial pressure driving force. With the proposed method, permeability is calculated from the total mass change and concentration change over time. Five replicate samples for each of three water concentrations (2, 5, and 20wt%) and three water-selective membrane types were tested at 50°C to assess method precision. Screening results were compared to those from prior bench-scale pervaporation experiments to assess accuracy. Water permeability was determined with good precision for all samples. Leak-tight crimp sealing of the vials was critical for good ethanol permeability precision results, particularly for membranes with a low water permeance or high water–ethanol permselectivity. Ethanol permeability accuracy was good for a non-swelling membrane material, but was poor for a swelling membrane material tested at the highest water concentration because of outward bulging of the unsupported exposed area of the membrane.