Hybrid Hollow Fiber Membranes Research Articles

Fabrication of highly selective hollow fiber membranes based on P84/PES blends for CO2/CH4 separation

AbstractIn this study, the aim was to purify CH4, an efficient and renewable clean energy source, which often contains CO2 that needs to be removed to improve its combustion efficiency. To achieve this, hybrid hollow fiber membranes were developed using BTDA‐TDI/MDI (P84) and polyethersulfone (PES) through a dry jet‐wet spinning process. The effects of different parameters, including core liquid composition, solidification bath composition and temperature, spinneret temperature, and air gap distance, were studied to optimize membrane structure, morphology, and CO2/CH4 separation performance. The P84/PES hollow fiber membrane obtained through this process demonstrated good CO2/CH4 separation performance, with CO2 permeation of 2.12 GPU and a selectivity of 51.23. To further improve the membrane's performance, a coating of poly(ether block‐amide) (PEBA) was applied to the P84/PES hollow fiber membrane. This modification resulted in a P84/PES‐PEBA hollow fiber membrane with increased CO2 affinity due to the polar poly(ethylene oxide) groups of PEBA. The P84/PES‐PEBA hollow fiber membrane exhibited high selectivity of 56.5 and CO2 permeance of 1.42 GPU at 25°C.

Study of a poly(vinylidene fluoride)/hydrophobic silica sol hybrid hollow fiber membrane for treatment of produced water via direct contact membrane distillation

Direct contact membrane distillation (DCMD) has shown great promises in remediating high-salinity oilfield produced water (PW). In our previous work, a hydrophobic silica sol (Si-R) was successfully synthesized to engineer anti-wetting ability of poly(vinylidene fluoride) (PVDF) membrane. Here our research interest lies in customizing PVDF hollow fiber membrane (HFM) with desirable stability for treating challenging oilfield PW via a DCMD process. The PVDF/Si-R hybrid HFM was fabricated under an optimized spinning condition. It is found that the fabricated PVDF/Si-R HFM is sandwich-structured, consisting a highly porous and thick middle layer and small-size macrovoids of outer layer and inner layer with different pore geometry, and the unique sandwich structure endows the membrane with superior wetting resistance. The membrane characterization showed that the liquid entry pressure (LEP) and water contact angle (WCA) of the fabricated PVDF/Si-R HFM impressively reached up to 5.25 bar and 126°, respectively. As a result, the PVDF/Si-R HFM possessed a desirable performance in treating high-salinity oilfield PW in terms of wetting resistance and salt rejection. Specifically, with a 60 h continuous DCMD operation, the PVDF/Si-R membrane exhibited over 99.9% salt rejection with only 7% reduction in permeate water flux. Clearly, the synthesized hydrophobic Si-R is a favorable additive for enhancing the antiwetting ability of PVDF HFM to treat high-salinity oilfield PW via DCMD process.

Tuning the surface properties of Fe3O4 by zwitterionic sulfobetaine: application to antifouling and dye removal membrane

In this paper, zwitterionic polysulfobetaine@Fe3O4 (PSBMA@Fe3O4) nanoparticles were synthesized via covalent grafting and free radical polymerization and characterized. The PSBMA@Fe3O4 noparticles had a zeta potential of − 36 mV (pH 6.3), which guaranteed the high colloidal stability. The as-synthesized nanoparticles were employed as a nanofiller to prepare superior antifouling polysulfone hybrid hollow fiber membranes. The FM-2 membrane exhibited the maximum pure water permeability of 61.1 L/m2 h bar with humic acid (HA) removal efficiency of 98%. The fouling resistance was evaluated using HA as a foulant, and the results suggested that the FM-2 membrane had less amount of HA adsorption with flux recovery ratio of 88.4%. Furthermore, the FM-2 membrane was demonstrated the reactive black-5 and reactive orange-16 removal of above 99% and 84% without much reduction in the dye solution permeability.

PVDF/SiO2-TiO2 Photocatalytic Membranes for Water Treatment

Polymeric membranes have been widely used for many kinds of wastewater treatment. However, the fouling of membranes decreases their permeability. TiO2 is widely used for water treatment because its photocatalytic properties, stability, availability and desirable hydrophilicity properties. In the recent years, many researchers have investigated the possibility of coupling polymeric membrane filtration technology and TiO2 photocatalysis to improve membrane performance by reducing fouling and increasing hydrophilicity. Because TiO2 particles on the membrane surface not only increase membrane hydrophilicity, but also create a photocatalytic property, formation of cake layer and blocking of membrane pores are prevented. So, the polymeric membranes with TiO2-based photocatalysts provide an opportunity for wastewater treatment.In previous studies, our group revealed that PVDF/TiO2 hybrid hollow fiber membrane through a phase inversion method to improve filtration efficiencies and antifouling properties.In the present work, SiO2 as inorganic material into PVDF membrane matrix increases the membrane permeability. SiO2 modified PVDF/TiO2 hybrid hollow fiber membrane is prepared by similar strategy. The membranes performances are evaluated based on the water permeability, humic acid (HA) rejection and antifouling properties. And this work focuses on the long-term stability and antifouling performance, especially under visible light.

Polyelectrolyte complexes/silica hybrid hollow fiber membrane for fusel oils pervaporation dehydration processes

Pervaporation as a tool to remove the residual water in biological resources, such as fusel oils (by-product of alcohol fermentation), is gaining increasing importance and consist with sustainable development well. In this study, polyelectrolyte complexes/silica (PEC/SiO2) hybrid hollow fiber membranes were prepared in situ via sol-gel process on polysulfone ultrafiltration support membrane. γ-glycidyloxypropyltrimethoxysilane (GPTMS) was introduced as precursor and crosslinker into poly (diallyldimethylammonium chloride)–sodium carboxymethyl cellulose complexes to form SiO2 particles in situ and enhance the interaction between inorganic and organic components. The physicochemical properties and morphology of the membranes were characterized by FT-IR, FESEM, EDS, etc. PEC/SiO2 membrane (PECM/SiO2) achieved an enhanced flux compared with the PEC pristine membrane without GPTMS. The membranes possessed a flux of 1332g/m2h and water content in permeate of 99.0wt% for the dehydration of fusel oils at 60°C. The effects of feed temperature and water content in feed on pervaporation performance were also investigated. Furthermore, the performance of PECM/SiO2 for the batch continuous dehydration application of fusel oils was more efficient than PERVAP-1001 commercial membranes. This approach provided a convenient way to prepare PEC/SiO2 hybrid hollow fiber membranes, which were potentially applied in fusel oils pervaporation dehydration processes.

Polyethersulfone/Cellulose Acetate Butyrate Hybrid Hollow-Fiber Membranes for Organic-Matter Removal From Produced Water

Summary In the US, for every barrel of oil, approximately 7 bbl of water is produced. Produced water consists of various amounts of organic and inorganic constituents from the source geologic formation and associated hydrocarbons. Produced-water handling has become a major effort for all waterflood operations. Membrane technology has been widely used for produced-water purification because of its economic and portable properties. However, the presence of organic matter in produced water causes serious membrane fouling, which shortens membrane life and increases operation costs. In this study, to reduce organic components in produced water, we fabricated a series of polyethersulfone (PES)/cellulose acetate butyrate (CAB) hybrid hollow-fiber membranes (HFMs) with different polymer-mass ratio for the removal of organic matter (benzene, toluene, octanoic acid, and hexanoic acid) from produced water. The morphology of the hybrid PES/CAB HFMs was characterized by scanning electron microscope (SEM) and atomic force microscope (AFM). The performance of the hybrid PES/CAB HFMs was evaluated in terms of permeate-water flux (PWF), organic-matter-removal efficiency, flux-decline ratio (FDR), and flux-recovery ratio (FRR). The results revealed that the PES/CAB hybrid HFMs comprised open-ended selective layers with homogeneous CAB distribution. Compared with neat PES HFM, the PES/CAB hybrid membranes exhibited 20.3% improvement of PWF. The organics-removal efficiency was higher than 99.8% for all the membranes. With 1.74 wt% of CAB in PES dope solution, the hybrid membranes possessed the lowest FDR and highest FRR, indicating the excellent antifouling ability of the PES/CAB HFMs. Because of these results, a two-stage antifouling HFM nanofiltration process was proposed as a follow-up work. The PES/CAB hybrid HFMs could serve as an attractive alternative for removing organic matter from produced water.

Study of PVDF/Si-R hybrid hollow fiber membranes for removal of dissolved organics from produced water by membrane adsorption

Abstract Polyvinylidene fluoride (PVDF) and hydrophobic silica sol (Si-R) hybrid hollow fiber membranes were fabricated by dry-jet wet spinning. The morphology and surface roughness of the PVDF/Si-R hybrid membranes were examined by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively. FTIR and contact angle analysis were used to characterize hydrophobic Si-R particles in the hybrid membrane. The membrane adsorption efficiency for dissolved organics including BETX (benzene, toluene, ethyl benzene and xylene) and two fatty acids: hexanoic acid and octanoic acid, as well as the membrane regeneration ability, were investigated by membrane adsorption experiments under different pressures, feed rates and temperatures. The results revealed that the hybrid hollow fiber membranes showed a microcellular structure rather than the typical asymmetrical structure of neat PVDF hollow fiber membranes. As the membrane collecting velocity increased, the hybrid hollow fiber membranes possessed enhanced surface roughness on both inner and outer surface. The adsorption efficiency of the PVDF/Si-R hybrid hollow fiber membrane was three times higher than that of the neat PVDF membrane. The adsorption efficiency of hybrid hollow fiber membranes increased with the increase of testing pressure; however, it decreased with the increase in feed rate, and was not influenced by temperature in the range of 0–80 °C. With membrane collecting velocity of 424 cm/min, the PVDF/Si-R hybrid membrane exhibited adsorption efficiency of 94.5% and 96.7% for benzene and octanoic acid, with membrane adsorption capacities of 208.1 mg/g and 173.9 mg/g. respectively. The hybrid membrane also showed high regeneration ability with 500 ppm benzene as feed solution. The PVDF/Si-R hollow fiber membrane offers an attractive possibility for the removal of dissolved organics in oilfield produced water.

Preparation of PVDF/CaCO3 hybrid hollow fiber membranes for direct contact membrane distillation through TIPS method

ABSTRACTPoly(vinylidene fluoride) (PVDF)–CaCO3 hybrid hollow fiber membranes with a cellular structure and prominent permeability were fabricated via the thermally induced phase separation method for membrane distillation. CaCO3 nanoparticles were introduced to the casting solution to improve the properties of the membranes. The effect of CaCO3 dosage on the morphology was investigated. The prepared membranes were characterized by differential scanning calorimetry, SEM, and atomic force microscopy. The results showed that liquid–liquid phase separation preceded solid–liquid phase separation during the spinning process. Low dosages of CaCO3 had a strong influence on the crystallization of PVDF molecules. The contact angle of the membrane increased with the addition of CaCO3 nanoparticles. The maximum dead end pure water flux was as high as 1295.5 L/(m2 h). The direct‐contact membrane distillation flux of the optimized PVDF/CaCO3 hybrid membrane achieved 63.98 kg/(m2 h) at the feed temperature of 90 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43372.

Preparation of heat-treated PAN/SiO2 hybrid hollow fiber membrane contactor for acetylene absorption

Abstract The heat-treated PAN/SiO 2 hybrid membranes were prepared through combining organic/inorganic blend and heat treatment methods for acetylene absorption process. The effect of SiO 2 contents (0.5, 1, 2 and 3 wt%), heat treatment temperature on the membrane morphology, structure and performance were investigated. The as-prepared membranes were characterized by FTIR, SEM, gas permeation test, hydrophobicity and mechanical stability. The results showed that the hybrid membranes had higher gas permeation properties due to their high pore sizes, porosities and thin skin layer. The membranes were further investigated as a membrane contactor for acetylene absorption using 1-methyl-2-pyrrolidinone (NMP) as absorbent. The acetylene absorption performance increased with increasing SiO 2 loading, and the acetylene mass transfer flux and absorption efficiency of the hybrid membrane contain 1 wt% SiO 2 were about 101% and 107% higher than the plain membrane at the same operating conditions, respectively.

Carbon Nanotube/Alumina/Polyethersulfone Hybrid Hollow Fiber Membranes with Enhanced Mechanical and Anti-Fouling Properties.

Carbon nanotubes (CNTs) were incorporated into alumina/polyethersulfone hollow fibre membranes to enhance the mechanical property and the efficiency of water treatment. Results show that the incorporation of CNTs can greatly limit the formation of large surface pores, decrease the void size in support layers and improve the porosity and pore connectivity of alumina/polyethersulfone membranes. As a result of such morphology change and pore size change, both improved flux and rejection were achieved in such CNTs/alumina/polyethersulfone membranes. Moreover, the CNTs/alumina/PES membranes show higher antifouling ability and the flux recoveries after being fouled by bovine serum albumin (BSA) and humic acid were improved by 84.1% and 53.2% compared to the samples without CNT incorporation. Besides the improvement in water treatment performance, the incorporation of CNTs enhanced the tensile properties of inorganic/polymer membranes. Therefore, such CNTs/alumina/PES hollow fiber membranes are very promising candidates for good filter media in industry, considering their high efficiency and high mechanical properties.

Preparation and Characterization of Polysulfone/Ru Nanocluster Hybrid Hollow Fiber Membrane

Polysulfone/Ru nanocluster hybrid hollow fiber membranes with different Ru content were fabricated by the dry/wet spinning process. The structures and properties of Ru nanocluster, PSF hollow films and PSF/Ru hybrid hollow fiber films were characterized by TEM, SEM, XPS, XRD, TGA, etc. The results showed that the Ru particles, which may coordinate with O and S in polysulfone, distributed symmetrically with an average diameter about 1~2 nm. More finger-like pores of the hybrid membranes were obtained after adding Ru nanocluster, and the thermal properties of the membranes increased while the mechanical properties decreased.

Thermally stable and solvent resistant self-crosslinked TiO2/PAN hybrid hollow fiber membrane fabricated by mutual supporting method

Organic/inorganic blend and self-crosslink reaction are elaborately incorporated to fabricate thermally stable and solvent resistant self-crosslinked TiO2/PAN hybrid membranes. This new fabrication method is a kind of mutual supporting technique which does not require a separate crosslinker or a catalyst. The prepared TPAN membrane shows excellent thermal stability which can persist up to 400°C without any large mass loss and has good solvent resistance in various boiling systems including N,N-dimethylacetamide. The hybrid membrane also holds a very big BET surface area of 8.36m2/g at 250°C and can be successfully used as structured packing for distillation to separate IPA/water mixture. An extremely low mass transfer time 1/(KGa) of 0.1s indicates that the hybrid membrane has excellent mass transfer performance. Similarly, for gas separation, because formed TiO2 can effectively reduce the pore size of membrane dense layer, the hybrid membrane also presents a good prospect in application under harsh environments.

Preparation and characterization of polyamide-6/CaCO3 hybrid hollow fiber membranes

Abstract Polyamide-6(PA6)/CaCO3 hollow fiber membranes were prepared by gel spinning from PA6/CaCO3/diluent system followed by cold-stretching. In virtue of the scanning electron microscopy (SEM), it is observed that the membrane present an asymmetric structure consisting of a dense skin, cellular cross-section and porous inner-surface. The porous structure was obtained by combining thermally induced phase separation (TIPS) process with interfacial micro-void mechanism, which has been seldom applied in membrane formation. Therefore, multi-porous structure derived from TIPS pores and interfacial micro-void. The Effects of CaCO3 content, fixed-length heat-setting on properties of hollow fiber membranes such as water permeability, porosity, bubble point pore diameter were investigated. In three different CaCO3 contents, the membrane with 30wt% CaCO3 has the best comprehensive performance. In addition, fixed-length heat-setting was favorable to produce membrane with higher water permeability.

The effect of binary diluents on the performance of ultrahigh molecular weight polyethylene/SiO2 hybrid hollow fiber membrane

AbstractUltrahigh molecular weight polyethylene (UHMWPE)/SiO2 hybrid hollow fiber membranes were prepared by thermally induced phase separation (TIPS) using mineral oil as the first diluent, polyethylene oxide (PEO) as the second diluent, and SiO2 as additive. The effect of PEO on the rheological behavior, FTIR‐ATR spectra, phase diagram, morphology, and permeability was investigated. The results suggested that a proper amount of PEO can decrease the viscosity of UHMWPE/diluent appropriately. Because PEO and UHMWPE were incompatible, the miscibility of membrane dope could be changed by PEO, which directly affect the phase separation. It was also discovered that a spherulite structure, coming from solid–liquid (S‐L) TIPS, was built at any UHMWPE concentration without PEO. Whereas, an open‐cell porous structure with better connectivity, owing to liquid–liquid (L‐L) phase separation, was produced after adding PEO. The permeability increased firstly, and then decreased because excessive PEO was sensitive for agglomeration. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Preparation and properties of polytetrafluoroethylene/CaCO3 hybrid hollow fiber membranes

AbstractA novel method of preparing polytetrafluoroethylene (PTFE) hollow fiber membrane was presented by utilizing poly (vinyl alcohol) (PVA) can form a gel of two dimensional complex compounds with Boric acid (H3BO3). Effects of H3BO3 on PTFE nascent hollow fiber were investigated, and the results showed that the introduction of H3BO3 effectively reduced the addition of PVA. The configuration named “fibril” formed between PVA and H3BO3 could be observed in nascent hollow fiber by SEM (Scanning electronic microscopy). Furthermore, Calcium carbonate (CaCO3) particles (60 nm∼ 90 nm) were introduced into PTFE matrix. The interfacial microvoids (IFMs) which were different from the PTFE sintering or node‐fibril network structure were obtained. The assumption of the IFMs formation was proposed in this study. Effects of CaCO3 amount and draw ratios on structure and properties of hybrid hollow fiber membranes were analyzed, and the SEM results showed that the IFMs quantity and diameter improved with draw ratio increasing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The Effect of Stretch on Multi-Pore-Structure of Ultrahigh Molecular Weight Polyethylene/SiO 2 Hybrid Hollow Fiber Membranes

Ultrahigh molecular weight polyethylene/SiO2 hybrid hollow fiber membranes were prepared by thermally induced phase separation (TIPS), using mineral oil as the diluent and SiO2 as the additive. The influences of heat-treatment, drawing ratio and drawing temperature on melting behavior, crystallization, multi-pore-structure (MPS) and porosity were investigated. The results of this study demonstrated that the original crystal grains became more perfect and that new micro crystallites were produced through heat treatment. Defects were more easily formed by the micro crystallites in cold stretching. Heat treatment also made the pores contract. The MPS including TIPS pore, stretching pore and interfacial microvoid was constructed after stretching. A model of interfacial microvoid was built. The model indicated that the area of interfacial microvoid increased as the drawing ratio became larger, reaching a maximum at a certain drawing ratio. Values above this maximum drawing ratio made no contribution to further increase the triangular area of interfacial microvoid but made many TIPS pores close. As the drawing ratio increased, the pore diameter ( PD) and total pore fraction ( TPF ) of the stretched pores increased whereas the TPF of the TIPS pores decreased. The pore diameter distribution ( PDD) and the porosity resulted from the joint effect of multiple pores. Without stretching, the porosity was slight due to the pores contracting, and it increased as the drawing ratio became larger, reaching a maximum at a drawing ratio of 5 times.

Phenol biodegradation in hybrid hollow-fiber membrane bioreactors

Hollow-fiber membrane bioreactors were developed with granular activated carbon (GAC) for the biodegradation of phenol using Pseudomonas putida. Hollow fibers showed similar structure with/without GAC incorporated; while GAC hollow fiber had a stronger phenol adsorption capacity. In batch biotransformation experiments, complete depletion of 1000 mg phenol l−1 (at which concentration free cells cannot grow) was accomplished in the reactor within 18 h in the hybrid bioreactor, comparing with 23 h in the GAC free bioreactor. Desorption and bioregeneration of the hollow-fiber membrane were believed to be the key for the enhancement of bioreactor performance. At continuous running, the GAC bioreactor showed its superiority over the GAC free bioreactor during start-up and elevated loading phase. More than 90% of the phenol was transformed in the GAC bioreactor when the phenol loading was <24 mg h−1. The better bioreactor performance may be due to the enhanced mass transportation and adsorption capacity with the incorporation of GAC.

Simulation study of a hybrid absorber–heat exchanger using hollow fiber membrane module for the ammonia–water absorption cycle

An innovative hybrid hollow fiber membrane absorber and heat exchanger (HFMAE) made of both porous and nonporous fibers is proposed and studied via mathematical simulation. The porous fibers allow both heat and mass transfers between absorption solution phase and vapor phase, while the nonporous fibers allow heat transfer between absorption solution phase and cooling fluid phase only. The application of HFMAE on an ammonia–water absorption heat pump system as a solution-cooled absorber is analyzed and compared to a plate heat exchanger falling film type absorber (PHEFFA). The substantially higher amount of absorption obtained by the HFMAE is made possible by the vast mass transfer interfacial area per unit device volume provided. The most dominant factor affecting the absorption performance of the HFMAE is the absorption solution phase mass transfer coefficient. The application of HFMAE as the solution-cooled absorber and the water-cooled absorber in a typical ammonia–water absorption chiller allows the increase of COP by 14.8% and the reduction of the overall system exergy loss by 26.7%.