Preparation of highly asymmetric hollow fiber membranes from poly(ether imide) by a modified dry–wet phase inversion technique using a triple spinneret (original) (raw)
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Recent progresses in polymeric hollow fiber membrane preparation, characterization and applications
Separation and Purification Technology, 2013
Membrane separation using hollow fibers has become one of the emerging technologies which underwent a rapid growth during the past few decades. In this article, recent progresses (last 12 years) on polymeric hollow fiber membranes have been discussed. In particular, the following topics were identified as the recent trends in the hollow fiber research. Characterizations of membrane especially by atomic force microscopy (AFM) have been reported. New hollow fiber membranes for gas-se paration have been developed. New polymers and techniques have been introduce d in making high performance hollow fibers. Many PVDF based membranes have been developed. Orientation of polymer molecule during spinning was also investigated. However the mechanism of orientation is not fully investigated.
Polymer, 2016
A porous poly (ethylene-chlorotrifluoroethylene) (ECTFE) membrane was prepared and evaluated in this study. Initially, solvent screening revealed diethyl phthalate (DEP) and glycerol triacetate (GTA) as proper solvents for the preparation of homogenous ECTFE solutions with the required properties for fabricating a hollow fiber membrane. The thermodynamic phase diagrams for both systems (ECTFE/DEP and ECTFE/GTA) showed a liquid-liquid (L-L) phase separation region, which is needed for a bicontinuous structure, prior to solid-liquid (S-L) phase separation (polymer crystallization). The ECTFE hollow fiber membranes were prepared by a thermally induced phase separation (TIPS) method using a unary solvent (DEP or GTA). The morphologies of hollow fiber membranes were observed by scanning electron microscopy (SEM) and it was observed that a bicontinuous structure was formed through L-L phase separation. The effect of the solvent types on properties of the prepared membrane such as water permeability and mechanical strength was discussed in detail. Moreover, the spherulite growth rate and crystallization degree were measured to assess the differences in the mechanical properties of the membranes prepared using DEP and GTA. In this study, with a polymer concentration of 20 wt%, the membrane showed a superior water flux and comparable mechanical properties with the ECTFE membranes already reported in published papers. Furthermore, the chemical resistance properties of ECTFE hollow fiber membranes were evaluated using the harsh treatments.
DESALINATION AND WATER TREATMENT, 2017
Preparation and properties of polyetherimide (PEI) hollow fiber membrane are described in a paper. PEI hollow fibers were produced on the spinning machine by phase inversion process. Experiments were designed with the aim to optimize the process parameters for the production of asymmetric polyetherimide hollow fibers. These parameters include polymer solution flow through the nozzle, bore liquid flow, air-gap distance, and the fiber take-up speed. CO 2 /CH 4 gas mixture permeation experiments were performed on produced membranes as well as the morphology studies by optical microscopy and scanning electron microscopy (SEM). The impact of the process parameters on the hollow fiber morphology and mixed gas transport and separation properties was investigated. Results show the critical influence of the bore liquid flow and the take-up speed on the fiber structure. With higher values of these parameters the membranes exhibited higher CO 2 /CH 4 selectivities. Tubular aspects of the fiber were obtained without deformations when high bore liquid flows were used. Smaller fiber diameters were achieved when the fiber take-up speed was higher.
Materials
Hollow fibers (HFs) are widely applied in different membrane operations, particularly in gas separation. The present work investigates the effect of post-spinning treatment on the gas transport properties of polyimide-based HFs. The membranes were spun by using both a conventional spinneret and a triple-orifice spinneret. A systematic analysis was carried out by considering different alcohols as the first fluid for the solvent exchange, with or without n–hexane as a second fluid. The HFs were characterized by exploring the change of the morphology and the permselective properties as a consequence of the operation conditions for spinning and post-treatments. According to the morphology, for a specific hollow fiber type, an optimal post–treatment was identified. The HFs prepared with the triple-orifice spinneret, using a solvent–rich shell fluid, can take advantage of the post-treatment using larger alcohols, while smaller alcohols should be preferred for the conventional spun HFs tha...
2021
Polyimide-based hollow fibers were spun using a triple orifice spinneret in order to apply them in gas separation. The membrane structure was tailored producing a porous external layer and a thin internal skin layer, that controlled the gas transport. The measurement of gas permeation rates and the morphological analysis were combined to obtain information on the performance of the membranes. The aim was to tune the inner top layer and investigate the role of the bore fluid on the gas permeation properties of the membranes. The bore fluid composition was explored by using water mixtures containing the solvent used for preparing the dope solution or a salt in order to reduce the water activity in the inner coagulant, but also a low amount of a crosslinker for improving the gas selectivity. The change of the dope flow-rate was also analyzed. At moderate dope flow-rates, the use of a saline water solution as bore fluid is more effective in enhancing the membrane gas selectivity with re...
Journal of Membrane Science, 2002
By using co-extrusion and dry-jet wet-spinning phase inversion techniques, we have developed delamination-free dual-layer asymmetric composite hollow fiber membranes for gas separation. Delamination-free is essential for dual-layer membranes to withstand high testing pressures. For concept demonstration, a 6FDA-durene-1,3-phenylenediamine (mPDA) (50:50) copolyimide was used to form the outer asymmetric separating layer, while polyethersulfone (PES) was employed to yield the inner interpenetrated porous supporting layer. A special assembly for outer-layer dope passage was firstly introduced into the dual-layer spinneret design in order to enhance the uniformity of dope distribution in nozzle orifice. A much thinner (≈10 m) and uniform outer layer was achieved. The effects of spinning conditions, such as spinneret temperature, air gap, bore fluid chemistry, inner-layer dope concentration and formulation, and solvent exchange on the interface delamination between the dual layers were examined. Inner-layer dope concentration and bore fluid composition as well as the sequent solvent exchange were found to play important roles to produce delamination-free dual-layer membranes. Pure gas test results show that the resultant 6FDA-durene-mPDA/PES dual-layer membranes have an O 2 /N 2 selectivity approaching to the intrinsic ideal selectivity value of 4.7 with a permeance of oxygen around 28 GPU (gas permeance unit) at room temperature, indicating the dual-layer hollow fiber membranes are apparently defect-free.
Journal of Membrane Science, 2004
Hollow fibers were spun from a polyetherimide (PEI) solution in n-methylpyrrolidone (NMP) and γ-butyrolactone (GBL) by using the dry–wet spinning method at different air-gaps. The ultrafiltration performance of hollow fibers was studied using aqueous solutions of polyethylene glycol of different molecular weights. The pure water permeation flux increased with an increase in the air-gap. Molecular weight cut off (MWCO) also increased with an increase in the air-gap. Significant difference between the inner and outer surface of the hollow fibers was observed by atomic force microscopy (AFM). Alignment of nodule aggregates in the direction of bore fluid (water) was observed at the inner surface. The roughness parameters decreased both at the inner and outer surface with an increase in the air-gap but the changing pattern was quite different. On both surfaces, the size of nodule aggregates decreased with an increase in the air-gap. As the roughness parameter decreases, the pore size increases. A plausible explanation has been made.
A Comparison between Several Commercial Polymer Hollow Fiber Membranes for Gas Separation
Journal of Membrane and Separation Technology, 2017
Polyethersulfone (PES), polyetherimide (Ultem ® 1000), and polyimide (Matrimid ® 5218) are common commercial polymers used to produce hollow fiber membranes for different gas separation applications. In this work, asymmetric hollow fiber membranes were prepared using these polymers by a phase inversion technique. The effects of spinning parameters (composition of the dope and bore solution, bore flow rate, air gap distance, temperature of the spinneret and coagulation bath, as well as take-up speed) on the membrane structure and gas permeation properties were investigated. The membrane separation performances were characterized by measuring their gas permeation properties (permeance and selectivity) for different gases (H2, CO2, O2, N2, and CH4) and by their cross-sectional morphology using scanning electron microscopy (SEM). The relationships between the gas separation performance of the hollow fibers and the intrinsic gas properties of the dense flat membranes made of the same materials were also studied. A comparison between the average apparent skin layer thickness calculated from O2 permeability/permeance, and the results based on SEM images was made and good agreement was obtained between both results.
Separation Science and Technology, 2017
Membrane-based separation is now established as one of staple technologies used in water treatment and reuse applications. Nanofiltration, in particular, can be a cost-effective solution for removing large ions and small molecular weight compounds from water. Nanofiltration membranes have been manufactured mostly as flat sheets and used in spiral wound modules. Hollow fiber geometry, however, offers several advantages over flat sheet and other configurations. This paper overviews recent developments in the design of hollow fiber nanofiltration membranes and provides a comparative analysis of two main methods of their fabrication-interfacial polymerization and phase inversion.