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

Abstract

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.

Poly(piperazine-amide)/PES Composite Multi-Channel Capillary Membranes for Low-Pressure Nanofiltration

“…This is consistent with a study by Misdan et al [ 41 ], who observed higher roughness of PA-coated membranes. Moreover, in a previous study [ 40 ] on the effect of coagulation medium composition, it was not possible to identify a clear trend in the surface structures with the addition of ethanol to the coagulation bath, which is confirmed in the presented AFM plots and data.…”

“…Both uncoated fibres show no salt rejection due to their UF characteristics. The higher permeate flux of the uncoated membrane prepared with pure water is attributed to fast demixing in the phase inversion process, whereas delayed demixing takes place when fractions of organic additives (ethanol) are added to the internal coagulation medium, resulting in denser support structures and lower flux [ 40 ]. The preparation procedure of support MCM was relatively robust, as independent preparation of MCM resulted in a relative standard deviation of permeate flux at 1 bar of 4.4% ( n = 4, post-treatment (PT) in 5000 ppm NaClO: one day) for BF W100 and 3.9% ( n = 3, PT one day) for BF W80E20, respectively.…”

Morphological characteristics of polymeric nylon‐6 film as biological recognition interface for electrochemical immunosensor application

“…The introduction of additive and adjustment of polymer concentration in casting dope are known to efficiently control the thin film morphology in enhancing the film performances. The additives can be water, inorganic additives, low‐molecular‐weight organics, surfactants, polymers, mineral filters, or a mixture of them . Ahmad et al .…”