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The development of a loose inner-selective polyethersulfone (PES) hollow fiber by one-step spinning process for nanofiltration (NF) has been demonstrated in this study. It is found that the addition of a small amount of sulfonated polysulfone (SPSf) and the use of a specially designed bore fluid made of hydrophilic additives such as polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) are of great importance to fabricate this type of NF membranes. Not only are they able to reduce the pore size but also suppress the formation of finger-like macrovoids. After optimizing both dope solution and spinning conditions, the as-fabricated membrane can have a 70% rejection to PEG 1000 and a pure water permeability (PWP) of 12.8 L m −2 h −1 bar −1 . Its rejection of indigo carmine (MW: 466 gmol −1 ) can reach 96.64%. In addition, it shows good stability in a continuous 76-h operation with good efficiency of dye removal. The newly developed membrane may have great potential in the treatment of textile wastewater. [ABSTRACT FROM AUTHOR]

Curved and structured membrane geometries are known to have the potential to reduce concentration polarization and fouling rates in membrane filtration and membrane contacting applications. However, their production is cumbersome and often comprises various successive processing steps. We present a new direct fabrication process of two new hollow fiber geometries: Curled and meandering hollow fibers. The phenomenon of liquid rope-coiling is adapted to a membrane spinning process resulting in mostly spiralling curly fiber geometries. Parameters influencing geometric properties are evaluated and experimentally obtained structures are presented. Fibers were prepared from a polyethersulfone-based polymer solution in an air gap spinning process. Prepared structured hollow fibers are investigated regarding geometrical measures and pore structures. A comprehensive analysis of the complex interplay between the influencing parameters is suggested. [ABSTRACT FROM AUTHOR]

Abstract: Due to the unique properties of amphiphilic Pluronic block copolymers, they have been blended with other polymers such as PVDF to prepare membranes. Considering the stability issue, the strong pore-forming ability of Pluronic F127, and the mechanical strength of the resultant membranes, Pluronic/LiCl mixed additive consisting of a very low concentration of Pluronic has been used in this study. The effects of spinning conditions on PVDF hollow fiber fabrication have also been studied. It is found that the use of merely 0.2wt% of Pluronic is sufficient to impose significant impacts on the morphology, filtration performance, and mechanical properties of the resultant fibers. Hollow fibers spun using higher coagulant temperature, higher take-up speed, and water as the bore fluid exhibit better mechanical properties and filtration performance. PVDF hollow fiber membranes with PWP of 1180L/m2 hMPa and MWCO of 5kDa were obtained when spun with optimized spinning conditions and using 3wt% of LiCl and 0.2wt% of Pluronic as the mixed additive. The fibers can withstand a pressure of 0.55MPa from the lumen. [Copyright &y& Elsevier]

Abstract: The charged poly(vinyl butyral) (PVB) hollow fiber ultrafiltration membranes were fabricated with perfluorosulfonic acid (PFSA) as additive by wet spinning method. Evolution of the precipitation kinetics, morphologies, permeation performances, electrokinetics and mechanical properties of the as-spun PVB membranes were investigated with the PFSA content and bore fluid. The results illustrate that the PVB/PFSA/N-methyl-2-pyrrolidone (NMP) dopes experience an instantaneous demixing mechanism and the precipitation rate increases with the addition of PFSA. The fibers fabricated with 50wt% ethanol aqueous solution as bore liquid have an asymmetrical double finger-like structure; nevertheless, the fibers fabricated with 90wt% NMP aqueous solution as bore liquid form a single finger-like structure. The PVB membranes containing more PFSA content and with 90wt% NMP aqueous solution as bore fluid have higher hydraulic permeability (J w ) than the fibers containing lower PFSA content and with 50wt% ethanol aqueous solution as bore fluid. The highest J w value 78.9LM−2 H−1 bar−1 is obtained for the PVB membrane with a MWCO of 50.1kDa. Streaming potential measurements verify that the apparent zeta potential (ζ app) of the PVB membranes fabricated with 50wt% ethanol aqueous solution as bore liquid ranges from −4.88mV to −11.28mV as PFSA content increases from 1wt% to 3wt%. The break strain and Young’s modulus values of the resultant fibers increase when the PFSA content increases regardless of the bore fluid. [Copyright &y& Elsevier]

Abstract: Porous stainless steel hollow fibers have been prepared via the dry–wet spinning process, based on phase inversion of a particle loaded polymer solution, followed by sintering. The morphology of the green fibers combines sponge like structures and macro voids, and is related to the dynamics of the phase inversion process. The morphology can be tuned by changing the spinning conditions and the composition of the spinning mixture. In analogy to their ceramic counterparts the morphology of the stainless steel fibers is preserved during sintering, apart from shrinkage due to densification. At a length scale comparable to the diameter of the steel particles the microstructure and related pore size distribution are more strongly affected by the sintering temperature, as compared to their ceramic counterparts. Sintering the stainless hollow fibers at temperatures>1100°C results in a sharp decrease in nitrogen permeance and an increase in bending strength, due to densification. The strength (∼1GPa) and nitrogen permeance (0.1mmolm−2 Pa−1 s−1 at 21°C) of stainless steel fibers sintered at 1050–1100°C are superior as compared to their ceramic counterparts. The excellent properties of the stainless steel hollow fibers make them suitable as membrane (supports) for applications involving harsh environments. [Copyright &y& Elsevier]