Wet Phase Inversion Method Research Articles

Fabrication and characterization of porous polyetherimide/montmorillonite hollow fiber mixed matrix membranes for CO2 absorption via membrane contactor

Asymmetric PEI hollow fiber mixed matrix membranes (MMMs) with improved structure and wetting resistance were fabricated via wet phase inversion method. The effects of incorporating hydrophobic MMT into polymer matrix in different loadings on the membrane properties were investigated. The membranes were characterized in terms of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), gas permeation test, hydrophobicity, wetting resistance and mechanical stability. All membranes possessed finger-like structures differing in skin layer thickness which increased with clay loading. The results revealed that the MMMs have significantly smaller pore size, higher porosity, hydrophobicity, LEPw and mechanical stability than plain PEI membrane. The membranes were further characterized by CO2 absorption test via contactor system using distilled water as absorbent and pure CO2 as solute gas. The results showed that the CO2 absorption performance increased with addition of MMT nano-clay. The membrane containing 1wt% MMT recorded the highest absorption flux of 2.35×10−3molm−2s−1 at the liquid velocity of 3ms−1, almost 135% higher than the flux of plain membrane at the same velocity. Comparatively, the flux of MMM was superior to several in-house made and commercial membranes.

Mixed‐matrix membranes based on polyurethane containing nanohydroxyapatite and its potential applications

ABSTRACTIn this study, new asymmetric polyurethane (PU) mixed‐matrix membranes with different nanohydroxyapatite loadings were prepared via a dry–wet phase inversion method by the dispersion of hydroxyapatite (HA) nanoparticles in the PU matrix. The HA nanopowder was obtained by a wet chemical precipitation method; it showed an average crystallite size of 58.3 nm, a specific surface area of 261 m2/g, and a pore size of about 1.6 nm. The effects of the HA loading (10–50 wt %) on the PU membrane characteristics were studied. The scanning electron microscopy images revealed that the HA nanoparticles were well dispersed enough in the PU matrix. The average pore size in the top layer and porosity of the membranes slowly decreased, whereas the hydrophilicity and water permeability increased with increasing content of HA. The evaluation of the nanofiltration performance was performed by investigation of the NaCl rejection. The composite membranes had a higher salt‐removal capacity than the unfilled PU membrane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41813.

Carbon dioxide stripping through water by porous PVDF/montmorillonite hollow fiber mixed matrix membranes in a membrane contactor

Hydrophobic montmorillonite-filled polyvinylideneflouride hollow fiber mixed matrix membranes were fabricated via wet phase inversion method to meet the requirements of stripping process through membrane contactor at elevated temperatures.

Polyurethane membrane with temperature- and pH-Controllable permeability for amino-acids

This work was focused on the investigation of the temperature- and pH-responsive polyurethane (PU) membranes and their permeability to amino-acids in response to environmental stimuli. The PU membrane was prepared from a wet phase inversion method and a two-step solution polymerization from polycaprolactone diols (PCL), 4,4'-diphenylmethane diisocyanate (MDI), dimethylol propionic acid (DMPA), etc. The chemical structure, phase state, morphology and surface wettability of the membrane were characterized with Fourier transform infrared (FTIR) spectrometer, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and contact angle tester, respectively. The temperature and pH responses of the membrane were investigated by means of an amino-acid permeate experiment. The L-phenylalanine (L-Phe) was chosen as model amino-acids. The permeation of the L-Phe was measured using a dead-end flow filtration at varied temperatures and pH, and characterized by the permeate flux (J) and rejection coefficient (R). J of the L-Phe across the PU membrane increased with increasing temperature and showed a sharp increase when temperature was raised to the crystalline melting temperature (T m ) of the soft segment of PU, while decreased with increasing pH and having a sharp decrease when pH reached the dissociation constant (pK a ) of DMPA contained in PU macromolecules. While, the R behavior of L-Phe was just opposite from the results of J, which decreased with increasing temperature and increased with increasing pH, also showing the temperature and pH responses. Hopefully, the PU membrane with temperature- and pH-controllable permeability has promising prospects in water treatment, membrane separation, drug delivery system, etc.

The impact of ZIF-8 particle size and heat treatment on CO2/CH4separation using asymmetric mixed matrix membrane

In this study, zeolitic imidazole framework 8 (ZIF-8) particles of different sizes were synthesized in aqueous media by varying the concentration of the base-type additive, triethylamine (TEA). ZIF-8 with particle sizes of ∼134 nm and ∼288 nm with surface areas of 418.44 m2 g−1 and 491.54 m2 g−1 were obtained without altering the crystalline structure. Synthesized ZIF-8 was further heat treated at 100 °C for a minimum of 12 hours, which led to an enhancement of its phase crystallinity and a surface area of 981.1 m2 g−1. Mixed matrix membranes (MMMs) were prepared via the dry–wet phase inversion method by dispersing as-synthesized ZIF-8s, heat-treated ZIF-8s and commercial ZIF-8 (∼493 nm) into a polysulfone (PSf) matrix. The thermal stability and mechanical strength of the membranes showed significant improvement after the incorporation of ZIF-8s. The MMMs were further subjected to the permeation experiments of CO2 and CH4. Although the majority of MMMs showed less selectivity than the neat PSf membrane, the incorporation of heat-treated ZIF-8 of the smallest size, exhibited CO2/CH4 selectivity of 28.5, which is significantly higher than the 19.43 obtained for the neat PSf membrane. Therefore, different ZIF-8 treatment protocols and particle sizes affect the MMMs performance significantly.

Effect of general montmorillonite and Cloisite 15A on structural parameters and performance of mixed matrix membranes contactor for CO2 absorption

Abstract Polyvinylideneflouride (PVDF) hollow fiber mixed matrix membranes (MMMs) were fabricated through wet phase inversion method using general MMT and Cloisite 15A as inorganic fillers. The effect of clay filler loadings (1, 3 and 5 wt% of polymer), their particle size and hydrophobicity on the membrane morphology, structure and performance in gas–liquid contacting process were investigated. The fabricated MMMs were characterized by scanning electron microscopic (SEM), gas permeation test, hydrophobicity, wetting resistance and CO2 absorption test. As expected, MMMs showed asymmetrical structure, differing in finger-like portion, porosity and pore size. The fabricated MMMs with higher finger-like area and surface porosity showed higher permeance than plain membrane. Furthermore, the wetting resistance in terms of surface hydrophobicity and liquid entry pressure of water increased with loading. From the point of view of physical CO2 absorption, the membranes incorporated with small particle size filler (general MMT-filled PVDF membranes) exhibited higher absorption fluxes than those embedded with large particle size fillers. The highest absorption flux for membrane containing 1 wt% general MMT is 1.0 × 10−3 mol m−2 s−1 at the flow rate of 3.1 m s−1. That flux was approximately 54% and 82% higher than the flux of MMMs with embedded Cloisite 15A of the same loading and plain PVDF membrane, respectively. The obtained flux of synthesized membrane was superior compared to several in-house made and commercial membranes.

Asymmetric membranes prepared with trifluoromethylphenylated poly(ether ether ketone) for gas separation

A series of asymmetric membranes based on a trifluoromethylphenylated poly(ether ether ketone) (CF3-PEEK) were prepared using a dry–wet phase inversion method. To obtain the asymmetric membranes with defect-free skin, the type and concentration of internal nonsolvent and the evaporation time were carefully investigated. The cross-section of membranes was characterized by scanning electron microscopy. The gas separation performance of asymmetric membranes was tested in terms of gas permeabilities and selectivities for helium, carbon dioxide (CO2), oxygen (O2), and nitrogen by the constant volume method. It was found that the permeabilities of asymmetric membranes were obviously higher than that of CF3-PEEK dense membrane. The membranes in series 2 showed higher permeability for each gas while the separability for gas pair CO2/O2 increased from 3.78 to about 6 comparing with that of the dense membrane.

Hollow fiber membrane process for the pretreatment of methane hydrate from landfill gas

Landfill gas is major source of green house effect because it is mainly composed of CH4 and CO2. Especially, the separation of CH4 from landfill gas was studied actively due to its high heating value which can be used for energy resource. In this study, polymeric hollow fiber membrane was produced by dry–wet phase inversion method to separate CH4 from the landfill gas. The morphology of the membranes was examined by scanning electron microscopy (SEM) to understand and correlate the morphology with the performance of the membrane. Firstly, single gas permeation and mixed gas separation were performed in lab-scale. After then, a pilot scale membrane process was designed using a simulation program. The manufactured process settled in Gyeong-ju landfill site and operated at various conditions. As a result, CH4 was concentrated to 88vol.% and also CO2 removal efficiency increases up to 86.7%.

Preparation and characterization of polysulfone mixed matrix membrane incorporated with palladium nanoparticles in the inversed microemulsion for hydrogen separation

Polysulfone (PSf) membrane shows acceptable gas separation performance, but its application is limited by the “trade-off” between selectivity and permeability. In this study, PSf mixed matrix membranes (MMMs) incorporated with palladium (Pd) nanoparticles in the inversed microemulsion were proposed for hydrogen (H2) separation. Pd nanoparticles can be kinetically stabilized and dispersed using electrostatic and/or steric forces of a stabilizer which is typically introduced during the formation of Pd nanoparticles in the inversed microemulsion. Pd nanoparticles were synthesized by loading (PdCl2) into the polymeric matrix, polyethylene glycol (PEG) which acts as reducing agent and stabilizer. The dry–wet phase inversion method was applied for the preparation of asymmetric PSf MMMs. The effects of Pd (0–4wt%) on the membrane characteristics and separation performance were studied. Experimental findings verified that the MMMs are able to achieved a high H2/N2 selectivity of 21.69 and a satisfactory H2 permeance of 46.24GPU due to the changes in membrane structure from fully developed finger-like structure to closed cell structure besides the growth of dense layer. However, the selectivity of H2/CO2 decreased due to the addition of PEG.

Effect of Cellulose Acetate Phthalate (CAP) on Characteristics and Morphology of Polysulfone/Cellulose Acetate Phthalate (PSf/CAP) Blend Membranes

Polysulfone (PSf) membrane is catogorized as hydrophobic membrane that easily fouled during membrane operation process. The presence of second hydrophilic polymer which added into membrane casting solutions plays a crucial role in adjusting the membrane properties. This hydrophilic polymer was employed in hydrophobic polymer membranes in order to improve hydrophilicity and performance as well as formed antifouling ultrafiltration (UF) membranes. In this study, a hydrophilic polymer, cellulose acetate phthalate (CAP) was added into polysulfone (PSf) membrane casting solutions by blending technique to produce PSf/CAP blend membranes. Flat sheet asymmetric PSf/CAP blend membranes were prepared by wet phase inversion method. The results revealed that an increase in CAP increased the hydrophilicity properties of PSf/CAP blend membranes compared to pure PSf membrane. The significant changes in size and numbers of microvoids and macrovoids in the morphological structures of PSf/CAP blend membranes were due to CAP promote the instantaneous liquid-liquid demixing during phase inversion process.

Enhanced Separation Performance of Cellulose Acetate Membrane For Brackish Water Separation Using Modification of Additives and Thermal Annealing

Membrane is an alternative technology of water treatment with filtration principle that is being widely developed and used for water treatment. The main objective of this study was to make an asymmetric membrane using cellulose acetate polymer and study the effect of additive and annealing treatment on the morphology structure and performance of cellulose acetate membranes in brackish water treatment. Asymmetric membranes for brackish water treatment were casted using a casting machine process from dope solutions containing cellulose acetates and acetone as a solvent. Membranes was prepared by phase inversion method with variation of polyethylene glycol (PEG) concentration of 1, 3, and 5wt% and the annealing temperature at 60oC and 70oC for 5, 10, and 15 seconds. Membrane characterization consists of calculation of membrane flux and rejection with brackish water as a feed, SEM and FTIR analysis. The research concluded that asymmetric cellulose acetate membrane can be made by dry/ wet phase inversion method. The more added concentration of PEG will be resulted the larger pore of membrane. Meanwhile the higher temperature and the longer time of annealing treatment, the skin layer of membrane become denser. Membrane with the composition of 18 wt% cellulose acetate, 5 wt% PEG, 1 wt% distilled water, with heat treatment at temperature of 70oC for 15 seconds is obtained optimal performance: flux 6.52 L.m -2 .h -1 .bar -1 , 71% of total dissolved solid (TDS) rejection, 63.75% of turbidity rejection, 52.9% rejection of Ca2+, and 41.9% rejection of Mg 2+

Porous polyethersulfone hollow fiber membrane in gas–liquid contacting processes

Porous polyethersulfone hollow fiber membranes were fabricated via dry–wet phase inversion method with the polymer concentration in the spinning dope either 13wt% or 15wt%. The fabricated hollow fiber membranes were characterized by different test methods and the performance of membranes in contactor applications was tested by CO2 absorption. The mean pore size, effective surface porosity and membrane porosity decreased while the membrane density and Liquid Entry Pressure (LEPw) increased as polymer concentration increased. The CO2 absorption flux of the fabricated membranes was measured in two cases; i.e. when the absorbent, distilled water, was in the lumen side or in the shell side. The CO2 flux for the membrane, fabricated from 13wt% PES solution, was compared with some commercial and in-house made membranes. The former membrane had 111% higher flux than a commercial PTFE membrane.

Manufacture and characteristics of asymmetric membrane capsule shells with a novel wet phase inversion method

In order to overcome the difficulty in stripping and to improve the automaticity and efficiency, a novel method was developed to prepare asymmetric membrane capsule shells (AM-CSs). Soluble mold pins were used to replace conventional insoluble mold pins, and simplified process was designed. Investigated by scanning electron microscopy and dye test, the homemade AM-CSs had typical asymmetric structure, in situ pore formation ability and high water influx. The in vitro dissolution properties of AM-CSs and homogeneous membrane capsule shells (HM-CSs) were compared. The release behavior of Metoprolol Tartrate and Nimodipine from the AM-CSs was mainly dominated by osmosis, while no drug could release from HM-CSs. The novel wet phase inversion method had significant advantages as well as potential value to be used in pharmaceutical research and application.

Effects of pore-forming additives on structures and properties of PVDF/Fe3+/Cu2+ hollow fiber membranes

The polyvinylidene fluoride (PVDF)/Fe3+/Cu2+ hollow fiber membranes were prepared via dry-jet wet phase-inversion method to investigate the effects of pore-forming additives on structures and properties of the membranes in this study. Using polyethylene glycol (PEG) (molecular weight: 400, 6,000, and 20,000 Da), polyvinyl pyrrolidone (PVP) K30, and glyceryl alcohol as pore-forming additives respectively, the membranes were fabricated with the dope solutions of PVDF/additive/Fe3+/Cu2+ when the temperatures of bore liquid/water bath were 60/40°C. The structures and properties of the membranes were characterized by microscope, measurement of pure water permeability (PWP), bovine serum albumin (BSA) rejection ratios, dry strength test and measurement of porosity. The results suggested that these membranes were single skinned external-pressure membranes. The resultant membranes with different organic additives were born with large and long finger-like macrovoids from inner surface. PVP K30 and glyceryl alcohol made the distribution of Fe3+/Cu2+ in PVDF nonuniform. The BSA rejection ratios of the resultant membranes decreased from 91.6 to 87.9 and 80.1% in parallel with the increase in PEG molecular weight from 400 to 6,000 and 20,000 Da, and PWP increased from 35 to 44 and 58 L m-2h-1 respectively. The optimal organic pore-forming additive is PEG 400. This study will give a reference to fabricate PVDF/Fe3+/Cu2+ hollow fiber membranes with high PWP, high rejection ratio, and high antifouling properties.

Effect of polymer concentration on the structure and performance of PEI hollow fiber membrane contactor for CO2 stripping

A series of polyetherimide (PEI) hollow fiber membranes with various polymer concentrations (13–16wt.%) for CO2 stripping process in membrane contactor application was fabricated via wet phase inversion method. The PEI membranes were characterized in terms of liquid entry pressure, contact angle, gas permeation and morphology analysis. CO2 stripping performance was investigated via membrane contactor system in a stainless steel module with aqueous diethanolamine as liquid absorbent. The hollow fiber membranes showed decreasing patterns in gas permeation, contact angle, mean pore size and effective surface porosity with increasing polymer concentration. On the contrary, wetting pressure of PEI membranes has enhanced significantly with polymer concentration. Various polymer concentrations have different effects on the CO2 stripping flux in which membrane with 14wt.% polymer concentration showed the highest stripping flux of 2.7×10−2mol/m2s. From the performance comparison with other commercial membrane, it is anticipated that the PEI membrane has a good prospect in CO2 stripping via membrane contactor.

Enhanced hydrophilicity and salt rejection study of graphene oxide-polysulfone mixed matrix membrane

Graphene oxide (GO) dispersed polysulfone (PSf) mixed matrix membranes were prepared by wet phase inversion method. The morphology of membranes was studied using scanning electron microscope (SEM) images. The variation in hydrophilicity was studied by measuring surface wettability and water swelling experiments. The performance of membranes in terms of pure water flux and salt rejection was studied. SEM images depict enhanced macrovoids, while the contact angle data reveals that, GO incorporated membrane surface is moderately hydrophilic. Membranes exhibited improved salt rejection after GO doping. Membrane with 2000ppm GO loading has exhibited maximum of 72% Na2SO4 rejection at 4bar applied pressure. The salt rejection seems to depend on pH of the feed solution and it has been witnessed that the salt rejection showed an increasing trend with increase in the pH.

Fabrication of a novel porous poly(vinylidene fluoride) blend five-bore membrane for wastewater treatment

Porous poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend five-bore hollow fiber membranes are prepared by wet phase inversion methods. In spinning these PVDF hollow fibers, N, N-dimethylacetamide (DMAc) and polyvinyl pyrrolidone (PVP) are used as the solvent and the non-solvent additive, respectively. The external coagulant uses water. The internal coagulants use water and DMAc-water solutions. The membranes are characterized in terms of water flux and molecular weight cut-off for the wet membranes. The cross-sectional structures are examined by scanning electron microscopy (SEM). The effects of polymer concentration and the internal coagulant on the permeation properties and membrane structures are examined keeping the bore liquid flow and air-gap constants. Relative high flux, rejection and strengh PVDF five-bore hollow fiber membranes could be prepared from the polymer concentration in dope solution at 17% of mass fraction, the air gap distance of 14 cm, and using 10% of mass fraction of DMAc solution as the internal coagulant at 13mL/min of flow.

Characterization of membranes prepared from PVDF/PAN blends and their modification with hydrolysis

In this study, the melt-spinning and stretching processes were used to prepare polyvinylidene fluoride (PVDF)/polyacrylonitrile (PAN) blend hollow-fiber membranes. These blend membranes have a higher tensile strength than those prepared via the wet phase inversion method. The influence of stretching temperature and draw ratios on the membrane microstructure, pure water flux, and porosity of the membranes was studied. The draw ratio and the stretching temperature can greatly affect the morphology and the permeation performance of the membranes. The Fourier transform infrared spectra demonstrate the differences in the PVDF/PAN blend membranes before and after hydrolysis. The water flux of the hydrolyzed PVDF/PAN blend membranes is sensitive to pH value and salt ionic strength. The effects of different salt ions on the permeability of the hydrolyzed membranes were also investigated.

Affinity between Metal–Organic Frameworks and Polyimides in Asymmetric Mixed Matrix Membranes for Gas Separations

A series of flat-sheet asymmetric mixed matrix membranes (MMMs) have been fabricated with MOF-5, Cu3(BTC)2, and MIL-53(Al) as fillers and PI polymer as a matrix through the dry–wet phase inversion method. After the surface modification by coating a PAA solution (15% wt) on the top of the obtained membrane, a thin defect-free selective skin in the MMM is obtained. The permeance of various gases such as H2, He, CH4, N2, and CO2 and their gas pair selectivity have been investigated, respectively. The results show that Cu3(BTC)2/PI MMM possesses the best gas separation performance with H2 permeance of 0.44 GPU and H2/CH4 selectivity of 100. In addition, the mechanism of MOF fillers in MMMs has been further revealed by the interaction analysis between MOF fillers and PI chains.

Rheology Assessment of PSf/ NMP Solution and its Influence on Membrane Structure

Asymmetric polysulfone membranes were prepared by wet-phase inversion method from casting solutions consisting of PSf/NMP and water as non-solvent. The effects of polymer concentration and molar mass were investigated by rheological studies. Moreover, membranes were characterized by scanning electron microscope (SEM). It was found that polymer solutions containing between 22 and 25 wt% PSf/NMP originated microfiltration membranes. The use of a higher mass molar polysulfone has been shown to reduce diameter pore and to maintain morphology. All the results were interrelated into a discussion of the skin formation of asymmetric membranes.