Influence of the coagulation medium on the performance of poly(ether sulfone) flat-sheet membranes

摘要

Poly(ether sulfone) flat-sheet membranes were fabricated via phase inversion with different nonsolvent mixtures. The effect of the nonsolvent water with the addition of various amounts of ethanol, acetone, or isopropyl alcohol on the membrane morphology (as measured with scanning electron microscopy and atomic force microscopy) and the filtration performance were investigated. For the statistical evaluation of the fabrication process, on average, six membranes were produced. The pure water flux (PWF) and macromolecule retention were determined via filtration experiments. The presence of coagulation additives resulted in modified precipitation kinetics and thermodynamics, yielded different membrane structures, and therefore, influenced the performance. The results show that the addition of ethanol, acetone, and isopropyl alcohol in low concentrations (up to 10%) to water led to an increasing PWF. Higher concentrations led to a decrease in PWF. For high concentrations (>30%), a change in the membrane morphology from fingerlike to spongelike structures was expected, and this was experimentally proven for the case of ethanol. One main finding was the similarity of the influence of the used additives on the membrane performance. This was to be expected from Flory-Huggins theory for additives with high water miscibility; hence, under these circumstances, entropic and not energetic reasoning dominated the phase-inversion process. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41645.