| 1. |
- Brinck, J, et al.
(author)
-
Influence of pH on the adsorptive fouling of ultrafiltration membranes by fatty acid
- 2000
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 164:1-2, s. 187-194
-
Journal article (peer-reviewed)abstract
- Fatty acids are found in many solutions treated in ultrafiltration plants, for example, in dairy products, fermentation broth, oily waste water and bleach plant effluents from pulp mills. The influence of fatty acids on the fouling of membranes is often ignored because their concentration is rather low. However, during recent years the significant influence of fatty acids on the flux reduction of ultrafiltration membranes has attracted much attention. The pore radius of the membrane, the concentration of fatty acids and the pH of the solution all have a profound influence on the flux reduction when treating solutions containing fatty acids. In the work presented in this paper, the influence of pH on the flux reduction of an ultrafiltration membrane made of polyethersulphone was studied. It was found that there was no flux reduction under alkaline conditions, whereas the flux reduction under acidic conditions was severe. In order to elucidate the adsorption process, the adsorption of octanoic acid on a planar, hydrophobized silica surface was studied by means of in situ null ellipsometry. In the ellipsometry study a sharp increase in the amount adsorbed was observed when the concentration of undissociated acid approached the saturation concentration as the pH was decreased. This explains the observed flux reduction under acidic conditions. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 2. |
- Amandusson, H., et al.
(author)
-
Hydrogen permeation through surface modified Pd and PdAg membranes
- 2001
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 193:1, s. 35-47
-
Journal article (peer-reviewed)abstract
- The hydrogen permeation through surface modified Pd and Pd70Ag30 membranes has been studied at temperatures between 100 and 350°C. Silver has been evaporated on Pd and Pd70Ag30 foils with a thickness of 25µm in order to study the role of the surface composition in comparison with the membrane bulk composition. The Pd70Ag30-based membranes display the largest permeation rates at temperatures below 200°C, while Pd membranes with 20Å silver evaporated on the upstream side show the largest permeation rates above 200°C. There are, consequently, different rate limiting processes above and below 200°C: at temperatures below 200°C, the bulk diffusion through the membrane is rate limiting, while at temperatures above 200°C, the influence of the surface composition starts to become significant. It has further been concluded that a sharp silver concentration gradient from the surface to the bulk is important for the hydrogen permeation rate at temperatures above 200°C. Adding oxygen to the hydrogen supply will almost totally inhibit the hydrogen permeation rate when a pure Pd membrane surface is facing the upstream side, while for silver-containing surfaces the presence of oxygen has almost no effect. On a clean Pd surface, oxygen effectively consumes adsorbed hydrogen in a water forming reaction. With Ag on the surface, no water formation is detected. Co-supplied CO inhibits the permeation of hydrogen in a similar manner on all studied membrane surfaces, independent of surface silver content. © 2001 Elsevier Science B.V. All rights reserved.
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| 3. |
- Hedlund, Jonas, et al.
(author)
-
A masking technique for high quality MFI membranes
- 2003
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 222:1-2, s. 163-179
-
Journal article (peer-reviewed)abstract
- A procedure for the preparation of high quality zeolite membranes was developed. This procedure relies on a masking approach that fills all support pores with wax while leaving the top surface free for deposition of the zeolite film, thus, protecting the support from the synthesis mixture. Zeolite films of different thickness were grown on masked and non-masked supports using a seeded growth method. The zeolite-coated supports were calcined in order to remove the wax from the support and the template molecules from the zeolite. The membranes were characterized by SEM, XRD, single gas and multi-component permeation measurements. Support masking reduces the zeolite membrane thickness and the width of the cracks in the zeolite film. Thicker films, especially those prepared without masking, are defective. Masked membranes with a film thickness of 500 nm show no cracks or pinholes. These membranes have a H2 permeance of 220×10−7 mol/(s m2 Pa), an n-butane permeance of 9.8×10−7 mol/(s m2 Pa) and an n-butane/iso-butane separation factor of 9.0 at 25 °C. The separation factor for a mixture of n-hexane/2,2-dimethyl-butane was 227 at 400 °C and the n-hexane permeance was 5.6×10−7 mol/(s m2 Pa). The p-xylene permeance was 2.7×10−7 mol/(s m2 Pa) and the para/ortho separation factor was 17 at 400 °C for a mixture of xylenes.
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| 4. |
- Hedlund, Jonas, et al.
(author)
-
ZSM-5 membranes synthesized without organic templates using a seeding technique
- 1999
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 159:1-2, s. 263-273
-
Journal article (peer-reviewed)abstract
- Porous α-alumina supports were seeded with colloidal TPA-silicalite-1 crystals and calcined. The supports were treated in a synthesis solution to grow the seed crystals into ZSM-5 films. The synthesis solution was free from organic template molecules in order to avoid the calcination step which often introduces cracks in the synthesized zeolite film. An SEM investigation indicated that the zeolite films on the supports were defect free and that the film thickness was approximately 1.5 μm. XRD data showed that the film consisted of well-crystallized ZSM-5. The permeance in single gas experiments decreased in the order H2O, H2, CO2, O2, N2 and CH4. The difference in permeance between each molecular species in the series was almost one order of magnitude which indicated that the membranes were of a high quality. Molecules larger than CH4 permeated with similar and low rates, independent of their kinetic diameters, indicating a non-selective permeation path through defects in the zeolite films. However, the permeance of these larger molecules was less than 1/10 000 of that for H2O. The highest measured separation factors for binary mixtures of N2/SF6 and H2/i-C4 were 110 and 99.
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| 5. |
- Mathew, Aji P., et al.
(author)
-
Transport of aromatic solvents through natural rubber/polystyrene (NR/PS) interpenetrating polymer network membranes
- 2002
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 20:1-2, s. 213-227
-
Journal article (peer-reviewed)abstract
- A series of interpenetrating polymer network membranes have been synthesised from natural rubber and polystyrene by the sequential polymerisation technique. The transport of aromatic hydrocarbons through semi- and full-interpenetrating polymer network membranes (IPNs) have been studied in detail by tracing the solvent uptake up to equilibrium. The sorption was carried out in a series of aromatic solvents viz. benzene, toluene and xylene. The effect of temperature on swelling is studied by carrying out the experiments in toluene in the temperature range of 30-75 °C. The effects of blend ratio, crosslinker content and nature of initiator on the diffusion of various solvents were analysed. It was found that in all cases, the uptake value increased by about 50% as the PS content decreased from 70-30%. The diffusion, sorption and permeation coefficients were evaluated. As the crosslink density was increased, the uptake decreased by 40%. Kinetic and thermodynamic parameters were evaluated from diffusion experiments. The diffusion profiles were compared with theoretical predictions. The influence of swelling on the mechanical performance of the membranes has been investigated by conducting tensile testing of swollen specimens.
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| 6. |
- Tantekin-Ersolmaz, S.B., et al.
(author)
-
Effect of zeolite particle size on the performance of polymer–zeolite mixed matrix membranes
- 2000
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 175:2, s. 285-288
-
Journal article (peer-reviewed)abstract
- The effect of zeolite particle size on the performance of silicalite–PDMS mixed matrix membranes is investigated at two different zeolite loadings. The separation properties of the membranes prepared are characterized by permeability measurements for O2, N2 and CO2 gases. The permeabilities of the silicalite–PDMS mixed matrix membranes are determined to increase with increasing particle size. The variations occurring in the permeability values with changes made in the particle size are much more pronounced at the higher zeolite loading. The ideal selectivity values corresponding to the mixed matrix membranes, on the other hand, generally seem to be less affected by the changes made in the particle size. The permeability values corresponding to the mixed matrix membranes exceed those pertaining to the original polymer membrane only at relatively higher zeolite loadings and/or for relatively larger particle sizes. The variations occurring in the permeabilities and selectivities with changes made in the zeolite particle size may be responsible for the different values of these parameters reported in the literature for the same types of zeolite filled polymeric membranes.
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| 7. |
- Aguilar-Sanchez, Andrea, et al.
(author)
-
Waterborne nanocellulose coatings for improving the antifouling and antibacterial properties of polyethersulfone membranes
- 2021
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 620
-
Journal article (peer-reviewed)abstract
- This article presents a waterborne nanocellulose coating process to change the surface characteristics and mitigate fouling of commercially available polyethersulfone (PES) microfiltration membranes. An extensive comparative study between nanoporous and nano-textured layers composed of cellulose nanocrystals (CNC) or TEMPO-oxidized cellulose nanofibrils (T-CNF), which were coated on the PES membrane by taking advantage of the electrostatic interactions between the PES substrate, a polyallylamine hydrochloride (PAHC1) anchoring layer, and the nanocellulose functional layer. Coated PES membranes exhibited decreased surface roughness and pore sizes as well as rejection of compounds with a M-w above 150 kDa, while the water permeability and mechanical properties of remained largely unaffected. The coatings improved the wettability as confirmed by a reduction of the contact angle by up to 52% and exhibited a higher negative surface charge compared to the uncoated membranes over a pH range of 4-8. A significant reduction in organic fouling was observed for the coated membranes demonstrated by bovine serum albumin (BSA) adsorption studies on T-CNF and CNC surfaces using Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), UV-vis spectroscopy and FTIR mapping after exposing the membranes to dynamic adsorption of BSA. The T-CNF coating exhibited effective antibacterial action against Escherichia coli (E. coli) attributed to the pH reduction effect induced by the carboxyl groups; while CNC coatings did not show this property. This work demonstrates a simple, green, and easy-to-scale layer-by-layer coating process to tune the membrane rejection and to improve antifouling and antibacterial properties of commercially available membranes.
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| 8. |
- Akhtar, Farid, et al.
(author)
-
Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H-2 separation performance
- 2015
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 493, s. 206-211
-
Journal article (peer-reviewed)abstract
- Graded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H-2 separation factor of 12 at 0 degrees C and a CO2 permeance of 21.3 x 10(-7) mol m(-2) s(-1) Pa-1 for an equimolar CO2/H-2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.
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| 9. |
- Andersson, Charlotte, et al.
(author)
-
Effects of exposure to water and ethanol on silicalite-1 membranes
- 2008
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 313:1-2, s. 120-126
-
Journal article (peer-reviewed)abstract
- The effects of long exposures to ethanol, water and 0.1 M aqueous solutions of ammonia, sodium hydroxide, tetrapropylammonium hydroxide (TPAOH) and hydrochloric acid on thin TPA-silicalite-1 membranes were studied. Single gas permeation experiments, porosimetry and scanning electron microscopy were used to characterize the membranes. It was found that a short exposure (24 h) will only dissolve synthesis residues and will not affect membrane quality negatively. The only medium that had an effect after 24 h was sodium hydroxide, which almost dissolved the film completely. After exposing TPA-silicalite-1 membranes for 30 days in the various liquids, the membrane quality decreased in the order ethanol < 0.1 M hydrochloric acid < 0.1 M TPAOH < water < 0.1 M ammonia < 0.1 M sodium hydroxide due to dissolution of the silicalite-1 crystals. This study has shown that prolonged exposure to aqueous solutions will lead to dissolution of silicalite-1 crystals causing an increase in micro- and mesopores in the film. The amount and size of the pores will depend on the pH of the aqueous medium. Higher pH gives a higher dissolution and hence more non-zeolitic pores in the silicalite-1 film. Ethanol has no effect on the dissolution of the zeolite film even after 30 days. This finding has an effect in membrane preparation and in several membrane applications such as pervaporation and separation of hydrocarbons isomer mixtures.
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| 10. |
- Arandia, Kenneth Gacutno, 1990, et al.
(author)
-
Fouling characteristics of microcrystalline cellulose during cross-flow microfiltration: Insights from fluid dynamic gauging and molecular dynamics simulations
- 2023
-
In: Journal of Membrane Science. - : Elsevier BV. - 1873-3123 .- 0376-7388. ; 669
-
Journal article (peer-reviewed)abstract
- The fouling behaviour of microcrystalline cellulose (MCC) particles on polyethersulfone (PES) membranes was investigated using fluid dynamic gauging (FDG) and molecular dynamics (MD) simulations. Experimental cross-flow microfiltration (MF) of a dilute MCC suspension at 400 mbar transmembrane pressure using 0.45 μm PES membranes revealed an estimated fouling layer thickness of 616 ± 5 μm for both fouled and re-fouled membranes at an applied shear stress of 37 ± 2 Pa. A decline in pure water flux was observed after each membrane cleaning and flushing procedure, indicating that highly resilient layers were formed close to the membrane surface. A possible explanation for the formation of resilient cellulose layers was obtained through MD simulations of the free energy profiles, which predicted deep energy minima at close interparticle separations of the cellulose–cellulose and cellulose–PES systems. The consequence of this energy minima is that attractive and repulsive forces are in balance at a specific distance between the particles, suggesting high binding energy at close interparticle distances. This implies that a certain force is needed to remove the layer or redisperse the cellulose particles. MD simulations also suggested that contributions made by repulsive hydration forces negatively influenced the adsorption of cellulose particles onto the PES membrane. These results highlight how experimental FDG measurements, when complemented with MD simulations, can provide insights into the fouling behaviour of an organic model material during cross-flow filtration.
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| 11. |
- Butylina, Svetlana, et al.
(author)
-
Fractionation of whey-derived peptides using a combination of ultrafiltration and nanofiltration
- 2006
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 280:1-2, s. 418-426
-
Journal article (peer-reviewed)abstract
- This paper describes the fractionation and further isolation and characterisation of peptides and proteins present in sweet whey by means of ultrafiltration using a regenerated cellulose membrane with a nominal molar mass cut-off value of 10 kg/mol and nanofiltration through sulphonated polyether sulphone membrane with a cut-off of 1 kg/mol. The concentration of whey proteins was done below the critical flux. The sieving coefficients for the whey components (proteins, lactose and salts) were estimated. Whey proteins were completely rejected by the ultrafiltration membrane. Size exclusion chromatography (SEC) and matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry were used to evaluate the molar masses of the peptide fractions that were present in the whey permeates. Nanofiltration of whey permeates obtained after ultrafiltration was conducted at two pH values (9.5 and 3.0) that corresponded to the different charged states of the membrane and of the peptides. The transmission of peptides, amino acids and lactose was found to be mainly affected by the permeability of the fouling layer. The selectivity of the nanofiltration membranes toward peptides compared to lactose was calculated as 0.82 and 6.81 at pH 9.5 and 3.0, respectively.
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| 12. |
- Cheng, Jie, et al.
(author)
-
Guanidimidazole-quanternized and cross-linked alkaline polymer electrolyte membrane for fuel cell application
- 2016
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 501, s. 100-108
-
Journal article (peer-reviewed)abstract
- A modified imidazole, namely guanidimidazole (GIm) was designed and synthesized as a novel quaternizing- and cross-linking agent for alkaline polymer electrolyte membrane fabrication. The resulting membrane was more alkali tolerant and swelling resistant than that quaternized purely by 1-methylimidazole owing to the enhanced resonance and cross-linking ability of GIm, the former confirmed by a LUMO (lowest unoccupied molecular orbital) energy calculation. The membrane also showed good ionic conductivity, mechanical strength and thermal stability. A H2/O2 fuel cell using the synthesized membrane showed a peak power density of 39 mW cm−2 at 50 °C. This work preliminarily demonstrates the beneficial effect of imidazole modification by both experimental and computational investigation; it provides a new cation design strategy that may potentially achieve simultaneous improvement of alkali-stability and swelling resistance of alkaline electrolyte membranes.
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| 13. |
- Dong, Qian
(author)
-
An experimental method to identify various oxygen species transported in oxides
- 2007
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 306:1-2, s. 166-172
-
Journal article (peer-reviewed)abstract
- Oxygen transport in oxides can take place in molecular, atomic and ionic form. An experimental method is described which separates the contributions of molecules, atoms and ions to the overall oxygen transport in oxides. The method comprises gas phase analysis and the use of oxygen isotopes O-16 and O-18. In the general case, exposure to non-equilibrated O-2 containing 60-70% O-18 is optimal to obtain the highest accuracy in the measurement. The method is exemplified by distinguishing non-ionic (molecular and atomic) oxygen transport from ionic oxygen transport in a commercial yttria-stabilized zirconia (YSZ) sample in the temperature range of 600-900 degrees C. There is approximately 35% molecular, 20% atomic transport and 45% ionic oxygen transport in YSZ at 600 degrees C. It is found that the fraction percent of non-ionic oxygen transport decreases with increasing temperature, and ionic oxygen transport increases sharply with increasing temperature.
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| 14. |
- Essalhi, Mohamed, et al.
(author)
-
Gamma-irradiated janus electrospun nanofiber membranes for desalination and nuclear wastewater treatment
- 2024
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 700
-
Journal article (peer-reviewed)abstract
- This study presents the fabrication of double-layer electrospun nanofibrous membranes (DL-ENMs) using polyvinylidene fluoride (PVDF) and polyether sulfone (PES) based polymers with different degrees of hydrophilicity (PES, sulfonated PES, and PES with hydroxyl terminals). A comparative analysis was carried out with single-layer electrospun nanofiber membranes (SL-ENM) with a total thickness of about 375 μm. Using feed solutions, including sodium chloride, sodium nitrate, and simulated nuclear wastewater (SNWW), the performance of DL-ENMs was evaluated for desalination and radionuclide decontamination by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) techniques. The results showed that DL-ENMs, especially those incorporating a sulfonated PES-based hydrophilic layer, exhibited superior permeate fluxes, reaching values of 72.72 kg/m2h and 73.27 kg/m2h in the DCMD using aqueous feed solutions of NaCl and NaNO3, respectively, and 70.80 kg/m2h and 41.96 kg/m2h using aqueous feed solutions of SNWW in DCMD and AGMD, respectively. Both SL-ENMs and DL-ENMs exhibited high rejection efficiencies and decontamination factors for the feed solutions (>99.9%). In addition, the prepared ENMs were exposed to gamma radiation to evaluate their applicability in real-life applications. The result of irradiation revealed the negative impact of gamma radiation on the fluorine content of PVDF which could be a critical point in using PVDF as a hydrophobic material for decontaminating nuclear wastewater by membrane distillation.
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| 15. |
- Essalhi, Mohamed, et al.
(author)
-
Gamma-irradiated janus electrospun nanofiber membranes for desalination and nuclear wastewater treatment
- 2024
-
In: Journal of Membrane Science. - : Elsevier B.V.. - 0376-7388 .- 1873-3123. ; 700
-
Journal article (peer-reviewed)abstract
- This study presents the fabrication of double-layer electrospun nanofibrous membranes (DL-ENMs) using polyvinylidene fluoride (PVDF) and polyether sulfone (PES) based polymers with different degrees of hydrophilicity (PES, sulfonated PES, and PES with hydroxyl terminals). A comparative analysis was carried out with single-layer electrospun nanofiber membranes (SL-ENM) with a total thickness of about 375 μm. Using feed solutions, including sodium chloride, sodium nitrate, and simulated nuclear wastewater (SNWW), the performance of DL-ENMs was evaluated for desalination and radionuclide decontamination by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) techniques. The results showed that DL-ENMs, especially those incorporating a sulfonated PES-based hydrophilic layer, exhibited superior permeate fluxes, reaching values of 72.72 kg/m2.h and 73.27 kg/m2.h in the DCMD using aqueous feed solutions of NaCl and NaNO3, respectively, and 70.80 kg/m2.h and 41.96 kg/m2.h using aqueous feed solutions of SNWW in DCMD and AGMD, respectively. Both SL-ENMs and DL-ENMs exhibited high rejection efficiencies and decontamination factors for the feed solutions (>99.9%). In addition, the prepared ENMs were exposed to gamma radiation to evaluate their applicability in real-life applications. The result of irradiation revealed the negative impact of gamma radiation on the fluorine content of PVDF which could be a critical point in using PVDF as a hydrophobic material for decontaminating nuclear wastewater by membrane distillation.
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| 16. |
- Fatemeh Seyedpour, S, et al.
(author)
-
Low fouling ultrathin nanocomposite membranes for efficient removal of manganese
- 2018
-
In: Journal of Membrane Science. - : Elsevier B.V.. - 0376-7388 .- 1873-3123. ; 549, s. 205-216
-
Journal article (peer-reviewed)abstract
- The key to make an ideal thin film composite membrane is the reduction of active layer thickness as much as possible to improve the water permeability without adverse effect on selectivity. Hence, ultra-thin nanocomposite membranes were prepared via dip coating method composed of chitosan incorporated graphene oxide on the surface of polyethersulfone (PES) substrate, followed by ionic crosslinking with sodium tripolyphosphate (TPP). By incorporation of graphene oxide on the chitosan solution, the thickness of selective layer considerably decreased to around 45 nm and higher surface hydrophilicity was obtained. The chitosan/graphene oxide ultra-thin modified nanocomposite membrane exhibited state-of-art flux (around 55 LMH) and high manganese removal (around 85%) at low pressure of 3 bar. Moreover, these membranes demonstrated up to 98% inhibition in the bacteria proliferation, indicating reasonable antibacterial activity of ultra-thin layer. Besides, the antifouling ability of the nanocomposite membrane increased dramatically, where the flux recovery ratio of 52% and 93% attained for BSA and E. coli, respectively.
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| 17. |
- Goetz, Lee, et al.
(author)
-
Superhydrophilic anti-fouling electrospun cellulose acetate membranes coated with chitin nanocrystals for water filtration
- 2016
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 510, s. 238-248
-
Journal article (peer-reviewed)abstract
- Electrospun cellulose acetate (CA) random mats were prepared and surface coated with chitin nano crystals (ChNC) to obtain water filtration membranes with tailored surface characteristics. Chitin nano crystals self-assembled on the surface of CA fibers into homogenous nanostructured networks during drying that stabilized via hydrogen bonding and formed webbed film-structures at the junctions of the electrospun fibers. Coating of CA random mats using 5% chitin nanocrystals increased the strength by 131% and stiffness by 340% accompanied by a decrease in strain. The flux through these membranes was as high as 14217 L m(-2) h(-1) at 0.5 bar. The chitin nanocrystal surface coating significantly impacted the surface properties of the membranes, producing a superhydrophilic membrane (contact angle 0) from the original hydrophobic CA mats (contact angle 132 degrees). The coated membranes also showed significant reduction in biofouling and biofilm formation as well as demonstrated improved resistance to fouling with bovine serum albumin and humic acid fouling solutions. The current approach opens up an easy, environmental friendly and efficient route to produce highly hydrophilic membranes with high water flux and low fouling for microfiltration water purification process wash water from food industry for biological contaminants.
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| 18. |
- Grahn, Mattias, et al.
(author)
-
Maxwell-Stefan modelling of High flux tubular silicalite-1 membranes for CO2 removal from CO2/H2 gas mixtures
- 2014
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 471, s. 328-337
-
Journal article (peer-reviewed)abstract
- In this work, a Maxwell-Stefan model for high flux tubular silicalite-1 membranes for separation of CO2 from a CO2/H2 mixture was developed. The model concerns tubular membranes operating in a counter flow module and includes transport through flow-through defects in the silicalite-1 film and pressure drop over the graded alumina support. Adsorption and diffusion parameters for perfect silicalite-1 crystals were taken from literature. The flux and selectivity predicted by the model were in reasonably good agreement with experimentally observed data for a ZSM-5 membrane without any fitting of the model. However, the CO2 flux and selectivity measured experimentally for the ZSM-5 membrane were higher than that predicted by the model for a silicalite-1 membrane.The model was used to investigate a case with a 20 000 Nm3/d feed comprised of a 50/50 mixture of CO2/H2 at pressure of 25 bar and a membrane temperature of 296 K. The permeate pressure was 1 bar and 90% of the CO2 permeated the membrane. In this case, the membrane permselectivity and CO2 flux varied along the length of the tubes between 20–26 and 950–396 kg/(m2 h), respectively. Further, both defects and pressure drop over the support were shown to have an adverse effect on the selectivity, which indicates that membrane selectivity can be improved by reducing the flow-through defects and/or by preparing supports with less flow resistance. For a one-stage process, the required membrane area is as small as ca 0.85 m2 and the hydrogen loss through the membrane was 12.4%. For a two-stage process the required membrane area almost doubled to 1.6 m2, however the hydrogen loss through the second membrane is reduced to as little as 2.5%. In summary, this work shows that high flux zeolite membranes may be an interesting option for CO2 removal from synthesis gas.
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| 19. |
- Gualtieri, Magdalena Lassinantti, et al.
(author)
-
Crack formation in α-alumina supported MFI zeolite membranes studied by in situ high temperature synchrotron powder diffraction
- 2007
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 290:1-2, s. 95-104
-
Journal article (peer-reviewed)abstract
- Cracks are frequently formed in α-alumina supported MFI membranes during calcination. To better understand crack formation, in situ powder diffraction data were collected during calcination of a type of MFI membrane (ca. 1800 nm thick) which is known to crack reproducibly. In addition, data for MFI powder and a blank support were also collected. Both a synchrotron radiation facility and an in-house instrument were used. The unit cell parameters were determined with the Rietveld method, and the strain in the direction perpendicular to the film surface was calculated for the film as well as for the support. The microstrain in the support was also estimated. Based on the results obtained here, a model for crack formation in this type of MFI membrane was proposed. The lack of cracks in other types of MFI membranes (ca. 500 nm) prepared in our laboratory is also explained by the model. In thicker MFI films, the crystals are well intergrown. During heating, the MFI crystals contract and the α-alumina support expands. Consequently, a thermal stress develops in the composite which eventually leads to formation of cracks in the film and structural defects in the support. In thinner films, the crystals are less well intergrown and the thermal expansion mismatch leads to opening of grain boundaries rather than cracks.
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| 20. |
- Gårdebjer, Sofie, 1985, et al.
(author)
-
The impact of interfaces in laminated packaging on transport of carboxylic acids
- 2016
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 518, s. 305-312
-
Journal article (peer-reviewed)abstract
- The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry.
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| 21. |
- Hedlund, Jonas, et al.
(author)
-
Mass transport in porous media from first principles : an experimental and theoretical study
- 2012
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 415-416, s. 271-277
-
Journal article (peer-reviewed)abstract
- In the present work, the mass transport of helium through zeolite is experimentally determined by measuring the flow of helium through a zeolite membrane. By using a mathematical model, the mass transport through defects was accounted for to arrive at mass transport through zeolite pores. For the first time, we could thereby experimentally show that the mass transport of helium in zeolite pores is strongly controlled by the amount and location of hydrocarbons in the zeolite pores and varies several orders of magnitude. The mass transport of helium in ZSM-5 zeolite pores is first reduced gradually more than one order of magnitude when the loading of n-hexane is increased from 0 to 47% of saturation. As the loading of n-hexane is further increased to 54% of saturation, the mass transport of helium in the zeolite pores is further reduced abruptly by more than two orders of magnitude. This gradual decrease followed by an abrupt decrease of mass transport is caused by adsorption of n-hexane in the zeolite pores. In a similar yet different fashion, the mass transport of helium in the zeolite pores is reduced abruptly by almost two orders of magnitude when the loading of benzene is increased from 0 to 19% of saturation due to adsorption of benzene in the pore intersections. Effective medium approximation percolation models with parameters estimated using density functional theory employing the local density approximation, i.e. models with no adjustable parameters and the most sophisticated theory yet applied to this system, can adequately describe the experimental observations.
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| 22. |
- Hedlund, Jonas, et al.
(author)
-
Permporometry analysis of zeolite membranes
- 2009
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 345:1-2, s. 276-287
-
Journal article (peer-reviewed)abstract
- In permporometry analysis of zeolite membranes, the permeance of a non-adsorbing gas, such as helium, is measured as a function of pressure of a strongly adsorbing compound, such as n-hexane in the case of silicalite-1 membranes. The adsorbing compound effectively blocks the transport of the non-adsorbing gas already at very low activity of the adsorbing compound. The plot of the permeance of the non-adsorbing gas as a function of relative pressure of the adsorbing compound is denoted a permporometry pattern. The present work is based on experimental data for a number of thin MFI membranes with a film thickness ranging from 300 to 1800 nm. An adsorption-branch permporometry experiment is simple and straightforward and after activation of the membrane by removing adsorbed species at 300 °C in a flow of dry gas, a full permporometry pattern is recorded within about 7 h for such membranes. It is shown how the distribution of flow-through defects can be estimated from the permporometry pattern using a simple model for permeation based on Knudsen diffusion. The estimated defect distribution is supported by SEM observations. In addition, the permeance of the non-adsorbing gas through defects measured in permporometry can be used to predict the permeance of molecules diffusing through defects in the membrane in mixture separation experiments and also indicate the separation factor. For instance, the helium permeance through defects in an MFI membrane measured by helium/n-hexane permporometry at room temperature can be used to estimate the permeance of 2,2-dimethylbutane (DMB) in a mixture separation experiment at a higher temperature with a feed containing both DMB and n-hexane by assuming Knudsen diffusion for both helium and DMB in the defects. Also, the separation factor αn-hexane/DMB in a mixture separation experiment at a certain temperature with an MFI membrane with a given defect distribution can be estimated from n-hexane/helium permporometry data recorded at the same temperature through an empirical correlation. In summary, adsorption-branch permporometry is a very effective tool for analysis of thin zeolite membranes, that in short time gives data that can be used to estimate the distribution of flow-through defects in the membrane and to estimate the transport of large molecules through defects in separation experiments and also estimate separation performance.
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| 23. |
- Hedlund, Jonas, et al.
(author)
-
The origin of the surface barrier in nanoporous materials
- 2022
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 641
-
Journal article (peer-reviewed)abstract
- Surface barriers are influencing the mass transfer in nanopores, but their origin is unclear and can be quite different in different materials. For MFI and CHA membranes studied here, we show that the surface barrier may be a surface diffusion process with higher activation energy than the surface diffusion process in the pores, but other possible mechanisms such as pore blocking and pore narrowing has not been ruled out. The higher activation energy is probably a result of less interaction between adsorbed molecules at the pore mouth than inside the pores, i.e. the barrier is simply a geometrical effect in these materials. For pure components at low concentration in MFI zeolite, we found that barrier is proportional to the product of the molecular weight and heat of desorption. For MFI and CHA zeolite, we observed that the barrier is a function of concentration and approach zero at high concentration and that the barriers of the components become more similar due to interaction between the components in mixtures, which explains the high and selective mass transfer displayed by these nanoporous materials at high concentration.
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| 24. |
- Henderson, R.K., et al.
(author)
-
Evaluation of effluent organic matter fouling in ultrafiltration treatment using advanced organic characterisation techniques
- 2011
-
In: Journal of Membrane Science. - : Elsevier BV. - 1873-3123 .- 0376-7388. ; 382:1-2, s. 50-59
-
Journal article (peer-reviewed)abstract
- Membrane fouling remains an operational challenge in the ultrafiltration (UF) membrane treatment of wastewater effluent and research is on-going to improve understanding of the organic character of foulants. Two advanced organic characterisation techniques that have potential to lend insight into membrane fouling are size exclusion chromatography with organic carbon, UV254 and nitrogen detection (LC-OCD) and fluorescence excitation-emission matrix (EEM) spectroscopy. In this study, UF treatment was undertaken for five tertiary wastewater effluents. The total hydraulic resistance was determined as well as that contributed by foulant layers fractionated by rinsing, backwashing and chemically desorbing. Organic characterisation for UF feed samples, permeates and each foulant layer was then performed using LC-OCD and FEEM spectroscopy with the aim of improving understanding of the character of foulants present in effluent organic matter (EfOM) and to determine the potential for the use of FEEM spectroscopy as a foulant indicator in such systems. It was determined that the biopolymer fraction was most significantly reduced on UF treatment, as anticipated due to its high molecular size. This was supported by the observation that the majority of the foulant layer comprised predominantly protein-enriched biopolymers (38-60% of total foulant layer DOC) that could be removed by rinsing. The resistance attributed to rinsing was directly related to the combined DOC concentration associated with proteins and low molecular weight neutral compounds as defined by LC-OCD analysis. Furthermore, tyrosine-like fluorescence intensity (λex/em=250/304nm) of both the rinsing solutions and UF feed samples showed good correlation with associated hydraulic resistance for EfOM originating from domestic wastewater, suggesting that fluorescence has potential to be used as a foulant indicator for these systems. © 2011 Elsevier B.V.
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| 25. |
- Ismail, Norafiqah, et al.
(author)
-
Investigating the potential of membranes formed by the vapor induced phase separation process
- 2020
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 597
-
Research review (peer-reviewed)abstract
- About 100 years ago, Zsigmondy and Bachmann invented a new method to induce phase inversion, the so-called vapor induced phase separation (VIPS). Since then many researchers have demonstrated this method in membrane fabrication. Here we present a review on membrane fabrication via VIPS to provide insights into membrane formation parameters in order to achieve desired properties for different applications. The key factors upon membrane preparation including solution parameters (i.e. polymer type and concentration, type of solvent, and additives) as well as operating parameters (i.e. exposure time, relative humidity, dissolution temperature, and vapor temperature) are comprehensively discussed. Furthermore, the design of a fouling-resistance membrane by the VIPS process has recently gained attention and is elaborated in details. The applications of the produced membranes via VIPS in water and wastewater treatment, gas separations, electrochemical applications (i.e. secondary batteries and supercapacitors) as well as in medical and biological applications are summarized and an outlook for future investigation is presented.
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| 26. |
- Ismail, Norafiqah, et al.
(author)
-
Non-ionic deep eutectic solvents for membrane formation
- 2022
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 646
-
Journal article (peer-reviewed)abstract
- Deep eutectic solvents (DES) have recently emerged as a new class of inexpensive biodegradable solvents and additives with diverse applications. In this study, a new family of non-ionic deep eutectic solvents (NIDES) is proposed for the first time for membrane preparation. Three types of NIDES, N-methylacetamide-acetamide (DES-1), N-methyl acetamide-N-methyl urea (DES-2), and N-methyl acetamide-N,N′-dimethyl urea (DES-3) were synthesized and used to dissolve polyvinylidene fluoride (PVDF) polymer. The effects of the additive polyvinylpyrrolidone (PVP) and the type of NIDES on the PVDF membrane characteristics, water permeability and bovine serum albumin (BSA) separation were studied. The membranes prepared with DES-1 and 2 wt% PVP exhibited a good water permeate flux (96.82 L/m2.h) and a high BSA separation factor (96.32%). High performance PVDF membranes can thus be efficiently prepared using biodegradable inexpensive NIDES.
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| 27. |
- Jalvo, Blanca, et al.
(author)
-
Coaxial poly(lactic acid) electrospun composite membranes incorporating cellulose and chitin nanocrystals
- 2017
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 544, s. 261-271
-
Journal article (peer-reviewed)abstract
- In this study, we used electrospinning to produce core-shell nanofibers of poly(lactic acid) as core and polyacrylonitrile/ cellulose nanocrystals (CNC) or polyacrylonitrile/chitin nanocrystals (ChNC) as shell. Electrospun materials prepared at different nanocrystal concentrations were tested and assayed as microfiltration membranes. The coaxial membranes presented a maximum pore size in the 1.2-2.6 mu m range and rejections > 85% for bacterial cells (0.5 x 2.0 mu m) and > 99% for fungal spores (> 2 mu m). The morphological and mechanical properties and the water permeability of the nanocomposite membranes were studied. The morphological characterization showed random fibers of beadless and well-defined core/shell structured fibers with diameter generally below the micron size with presence of secondary ultrafine nanofibers. Tensile strength and Young's modulus of elasticity improved with respect to coaxial membranes without nanocrystals with best mechanical properties achieved at 5 wt% CNC and 15 wt% ChNC loadings. The enhancement was attributed to the reinforcing effect of the percolating network of cellulose nanocrystals. Water permeability increased for all membranes loaded with nanocrystals with respect to the coaxial fibers without nanocrystals, the highest corresponding to ChNC composites with up to a 240% increase over non-loaded membranes. Composite membranes prepared with CNC in their shell were hydrophilic, in contrast with the hydrophobic PLA core, while coaxial fibers with ChNC were superhydrophilic. CNC membranes were negatively charged but ChNC originated neutral or positively charged membranes due to the contribution of deacetylated chitin structural units. Upon exposure to E. coli cultures, composite membranes containing ChNC showed a high antimicrobial action and were essentially free of bacterial colonization under strong biofilm formation conditions.
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| 28. |
- Jareman, Fredrik, et al.
(author)
-
Modelling of single gas permeation in real MFI membranes
- 2004
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 236:1-2, s. 81-89
-
Journal article (peer-reviewed)abstract
- A novel permeation model for flow through defects and zeolite pores in real MFI membranes, also accounting for substrate effects has been developed. Defect distributions for two types of MFI membranes were determined from porosimetry data using the model, which incorporated the Horvath Kawazoe (micropores) or the Kelvin equation (mesopores). The narrowest (1.08 nm) and also most common defects were found to be separated with a distance of 10–40 μm according to the model. Diffusion coefficients for hydrogen, helium, nitrogen and SF6 in the zeolite were further determined from single gas permeation data using the model using the independently determined defect distribution. The coefficients are consistent with values previously reported in the literature.
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| 29. |
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| 30. |
- Kangas, Jani, et al.
(author)
-
Maxwell-Stefan modeling of the separation of H2 and CO2 at high pressure in an MFI membrane
- 2013
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 435, s. 186-206
-
Journal article (peer-reviewed)abstract
- In the present study, a Maxwell-Stefan based model was developed for the separation of CO2 from H2 at high pressure in an MFI membrane. The usage of the Vignes interpolation formula for mixture surface diffusivities together with the IAST (ideal adsorbed solution theory) using bulk gas phase fugacities for mixture adsorption proved to be a feasible combination for this case. Both the effects of defects in the zeolite film and the mass transfer resistance caused by the support layers were studied and included in the model. Only pure component experimental data was used in the model building to predict the gas mixture permeation. The fitted diffusion parameters were in line with the literature values. The occupancy fraction dependence of CO2 surface diffusivity was utilized for the first time in the prediction of binary separation of H2/CO2 at high pressure on a real MFI membrane. Usage of an occupancy fraction dependence for CO2 surface diffusivity improved the model predictions. The adsorption parameter fitting for hydrogen based on the permeation measurements resulted in a feasible adsorption model, but should be used with caution. The model predicts binary separation measurement results relatively well. Both defects and support have a noticeable impact on the overall performance of the membrane.
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| 31. |
- Karim, Zoheb, et al.
(author)
-
Nanocellulose based functional membranes for water cleaning : Tailoring of mechanical properties, porosity and metal ion capture
- 2016
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 514, s. 418-428
-
Journal article (peer-reviewed)abstract
- Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers suspensions followed by dip coating with cellulose nanocrystals having sulphate or carboxyl surface groups. It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes via control of drying conditions and acetone treatment. Cellulose nanofibers coated with cellulose nanocrystal with carboxyl surface groups showed the highest tensile strength (95 MPa), which decreased in wet conditions (approximate to 3.7 MPa) and with acetone (2.7 MPa) treatment. The membrane pore sizes, determined by nitrogen adsorption/desorption were in nanofiltration range (74 angstrom) and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194 angstrom) with a concomitant increase (7000%) of surface area. The water flux, also increased from zero to 25 L m(-2) h(-1) at a pressure differential of 0.45 MPa, for acetone treated membranes. Modeling of the permeance showed that the middle layer of cellulose nanofibers was responsible for the majority of the resistance to flux and the flux can be improved by increasing the porosity or decreasing the thickness of this layer. The membranes irrespective of the surface functionality showed exceptional capability (approximate to 100%) to remove Ag+, Cu2+ and Fe3+/Fe2+ ions from mirror industry effluents. Surface adsorption followed by micro-precipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultra filtration membranes with high rejection towards metal ions.
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| 32. |
- Karimi, Somayeh, et al.
(author)
-
A simple method for blocking defects in zeolite membranes
- 2015
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 489, s. 270-274
-
Journal article (peer-reviewed)abstract
- The abatement of defects in zeolite membranes is essential for achieving high selectivity. In the present work, a simple and effective method for blocking defects in ultra-thin (ca. 0.5 μm) MFI zeolite membranes has been developed. The method is based on deposition of an ultra-thin (∼15 nm) layer of amorphous silica on the top surface of the membrane. Permporometry data indicated that the amount of defects, especially defects larger than 4 nm, in the membranes was significantly reduced after the modification. In mixture separation experiments, the CO2/H2 separation factor increased dramatically after blocking the defects in a defective membrane that was selected for the experiments. For instance, at 263 K and 9 bar feed pressure, the CO2/H2 separation factor increased from 8.5 to 36 after modification of the membrane, whereas the CO2 flux only decreased by ca. 40%.
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| 33. |
- Karimi, Somayeh, et al.
(author)
-
High flux acetate functionalized silica membranes based on in-situ co-condensation for CO2/N2 separation
- 2016
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 520, s. 574-582
-
Journal article (peer-reviewed)abstract
- Acetate-functionalized silica membranes were prepared via co-condensation. The molar ratio of functional groups in the silica matrix was varied in the range of 0–0.6, denoted by x. The presence of functional groups bonded to the silica network was revealed by FTIR and 29Si and 13C solid-state NMR analysis. The stability of the groups was studied by TG analysis. The membranes were evaluated for CO2/N2 mixture separation in a temperature range of 253–373 K using a feed pressure of 9 bar and a sweep gas kept at atmospheric pressure on the permeate side. The membranes were found to be CO2-selective at all the conditions studied. The highest observed selectivity was 16 for x=0.4, with a CO2 permeance of 5.12×10−7 mol s−1 m−2 Pa−1. For x=0.2, a permeance of as high as 20.74×10−7 mol s−1 m−2 Pa−1 with a CO2/N2 selectivity of 7.5 was obtained. This permeance is the highest reported for CO2/N2 separation using functionalized silica membranes. It is proposed that the separation mechanism between CO2 and N2 was the preferential adsorption of CO2, which inhibited adsorption and permeation of N2 through the silica pore network. Permporometry results revealed that as the loading of functional groups increased, the He permeance decreased. It was also indicated that the quantity of micropores in the functionalized membrane was higher than that in the parent silica membrane.
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| 34. |
- Khataee, Amirreza, et al.
(author)
-
Poly(arylene alkylene)s functionalized with perfluorosulfonic acid groups as proton exchange membranes for vanadium redox flow batteries
- 2023
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 671
-
Journal article (peer-reviewed)abstract
- With the aim to develop vanadium redox flow battery (VRFB) membranes beyond state of the art, we have in the present work functionalized poly(p-terphenylene)s with highly acidic perfluorosulfonic groups and investigated their performance as proton exchange membranes (PEMs). Consequently, two poly(p-terphenylene alkylene)s tethered with perfluoroalkylsulfonic acid and perfluorophenylsulfonic acid, respectively, were synthesized through superacid-mediated polyhydroxyalkylations and cast into PEMs. Compared with Nafion 212, the PEM carrying perfluorophenylsulfonic acid groups (PTPF-Phenyl-SA) was found to exhibit higher ionic conductivity and eight times lower vanadium (IV) permeation rate. The latter explains the longer self-discharge duration of the VRFB based on the PTPF-Phenyl-SA. In addition, the VRFB assembled with the PTPF-Phenyl-SA PEM exhibited a high average coulombic efficiency of 99.6% for over 100 cycles with a capacity fade of 0.24% per cycle, which was 50% lower than when Nafion 212 was used. More importantly, excellent capacity retention was achieved through electrochemical rate performance experiments at different current densities.
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| 35. |
- Korelskiy, Danil, et al.
(author)
-
Characterization of flow-through micropores in MFI membranes by permporometry
- 2012
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 417-418, s. 183-192
-
Journal article (peer-reviewed)abstract
- Permporometry was used for the first time to characterize flow-through micropore defects down to 0.7 nm in size in MFI zeolite membranes. Helium was used as the non-adsorbing gas and n-hexane or benzene was used as the adsorbate. The helium flow through zeolite pores was estimated using percolation theory and the remaining flow was assigned to flow-through defects. The area distribution of flow-through defects was estimated from the data using a simple model and similar results were obtained using both adsorbates. The total area of defects determined using n-hexane as the adsorbate was as low as about 0.7% of the membrane area and defects with a width below 1 nm constituted 97% of the total defect area for the best membrane. The permporometry results were supported by n-hexane/1,3,5-trimethylbenzene separation experiments. The permporometry data were also consistent with HR-SEM observations indicating the presence of narrow open grain boundaries, and absence of large cracks and pinholes
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| 36. |
- Korelskiy, Danil, et al.
(author)
-
High flux MFI membranes for pervaporation
- 2013
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 427, s. 381-389
-
Journal article (peer-reviewed)abstract
- MFI membranes with a thickness of 0.5 μm prepared on a graded α-alumina support were evaluated for separation of feed mixtures of 3 wt.% n-butanol/water and 10 wt.% ethanol/water by pervaporation. The membranes were selective to n-butanol and ethanol. The flux observed in the present work was about 100 times higher than that previously reported for n-butanol/water separation by pervaporation and about 5 times higher than that for ethanol/water separation by pervaporation. At 60 °C, the observed n-butanol/water flux was about 4 kg m−2 h−1 and the n-butanol/water separation factor was about 10 for the best membrane. At the same temperature, the membrane displayed an ethanol/water flux of ca. 9 kg m−2 h−1 and an ethanol/water separation factor of ca. 5. A mathematical model indicated significant mass transfer resistance in the support, which reduced the flux and the selectivity of the membranes.
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| 37. |
- Lewis, William, et al.
(author)
-
Investigation of cake fouling and pore blocking phenomena using fluid dynamic gauging and critical flux models
- 2017
-
In: Journal of Membrane Science. - : Elsevier BV. - 1873-3123 .- 0376-7388. ; 533, s. 38-47
-
Journal article (peer-reviewed)abstract
- Cake growth during a low pressure cross-flow microfiltration (MF) of a Kraft lignin suspension was studied using fluid dynamic gauging (FDG). This is the first paper to discuss the identification of fouling mechanisms and their transition points based on simultaneous, in situ and in real-time FDG measurements of cake layer thickness and flux. The FDG results were used to quantify the significance of membrane pore-level fouling phenomena which occur at an early stage of the filtration. A flux decline of approximately 75% was attributed to membrane pore fouling i.e. deposition on the surface of the membrane which caused direct blocking of the membrane pores. We present here a novel toolset for quick and achievable diagnosis of membrane fouling mechanisms, which can accelerate innovations in membrane technology and process optimisation. Furthermore, this innovative approach showed good agreement with a mathematical approach, based on a critical flux model, which was applied to raw flux data. In addition to cake thickness measurements, destructive strength testing of the fouling layer showed an increase in cohesive strength over time. The results showed that filter cakes formed by Kraft lignin become harder to remove by shear stress as they become thicker during the course of the filtration. A removal mechanism for lignin layer under stress is also proposed. The methodology described here can be applied to rapidly predict and assess routes to performance improvements in cross-flow MF.
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| 38. |
- Lindmark, Jonas, et al.
(author)
-
Carbon dioxide removal from synthesis gas using MFI membranes
- 2010
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 360:1-2, s. 284-291
-
Journal article (peer-reviewed)abstract
- A membrane processes may represent a more effective alternative compared to current technology for separation of CO2 from synthesis gas. In the present work, MFI membranes were prepared and the separation performance was evaluated. The Si/Al ratio and the counter ions in the membrane had a significant effect on both single gas permeation and mixture separation by modifying both the effective pore size and the adsorption properties of the membranes. The membranes were relatively unselective for binary mixtures of carbon dioxide and hydrogen, but when the feed also contained water, a CO2/H2 separation factor of 6.2 was achieved for a BaZSM-5 membrane at room temperature. The CO2 permeance for this membrane was as high as 13·10-7 mol · m-2 · s-1 · Pa-1. A suitable terminology for this effect, that a third component, in this case water, enhanced the separation of two other components, in this case CO2 and H2, is sorption enhanced separation. Due to the reduced adsorption of both CO2 and water at higher temperature, the CO2/H2 separation factor was always reduced as the temperature was increased. This work clearly shows that MFI membranes are promising candidates for CO2 separation from synthesis gas.
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| 39. |
- Lindmark, Jonas, et al.
(author)
-
Impregnation of zeolite membranes for enhanced selectivity
- 2010
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 365:1-2, s. 188-197
-
Journal article (peer-reviewed)abstract
- A new method to enhance the selectivity of zeolite membranes for alternative separation tasks has been developed. Calcined MFI membranes were impregnated with a solution of Ca(NO3)2 in methanol and calcined at 600 °C to thermally decompose the nitrate. SEM and EDS data indicated that calcium compounds were evenly distributed in the entire MFI film and in addition, a few crystals of a calcium compound were observed on top of the film in some locations. A HR-TEM investigation showed that calcium compounds were present in low concentration in the sample and that the interiors of the MFI crystals remained fully crystalline after impregnation and calcination. However, the HR-TEM investigation could neither confirm nor rule out the occurrence of calcium compounds in the pores in the interiors of the crystals. In accordance with the SEM and TEM observations, XRD data showed that calcium compounds on top of the film were relatively large CaCO3 crystals and that the zeolite film remained crystalline after impregnation. However, eventual calcium compounds in the pores of the zeolite could not be studied by XRD since these would probably generate a very weak signal of amorphous material. FTIR data indicated that impregnation increased the amount of both physisorbed and chemisorbed CO2, the latter resulting in carbonate species in the film. n-Hexane/helium adsorption branch permporometry showed that the high quality of the membranes remained after modification. The single component permeance ratio CO2/H2 increased from 0.6 to 1.5 after impregnation. Calculations indicated that the increased CO2/H2 single component permeance ratios were both an effect of increased adsorption of CO2 in the film and reduced pressure drop in the support. The dual component separation factor α CO2/H2 at room temperature increased drastically from 0.7 (H2 selective) to 3.4 (CO2 selective) after impregnation. This work shows for the first time that impregnation procedures can be used to tailor the diffusion properties of zeolite membranes in a similar way as impregnation procedures are used to tailor the catalytic performance of catalysts.
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| 40. |
- Lu, Yahua, et al.
(author)
-
Heterostructure membranes of high permeability and stability assembled from MXene and modified layered double hydroxide nanosheets
- 2023
-
In: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 688
-
Journal article (peer-reviewed)abstract
- Two-dimensional (2D) MXene-based lamellar membranes play transformative roles in membrane filtration technology. Their practical use in water treatment is however hindered by several hurdles, e.g., unfavorable swelling due to weak interactions between adjacent MXene nanosheets, tortuous diffusion pathways of layered stacking, and the intrinsic aquatic oxidation-prone nature of MXene. Herein, nanoporous 2D/2D heterostructure membranes are elaborately constructed via solution-phase assembly of oppositely charged MXene and modified layered double hydroxide (MLDH) nanosheets. As a multifunctional component, positively charged holey MLDH nanosheets were first tailor-made to serve simultaneously as a binder, spacer and surface-modifier; next they were intercalated into negatively charged MXene lamella to enhance structural stability and mass transfer of membranes. As a result, the as-prepared MLDH@MXene heterostructure membranes successfully break the persistent trade-off between high permeability and selectivity while mitigating the common drawbacks in 2D MXene-based lamellar membranes, e.g., swelling issues, restacking problems, and vulnerable chemical stability. Noticeably, at an operating pressure of 4 bar and a feed solution of 100 ppm of Congo red, the heterostructure membranes enable a threefold jump in permeability (332.7 +/- 20 L m(-2) h(-1 )bar(-1)) when compared to the pristine MXene membrane (119.3 +/- 18 L m(-2 )h(-1) bar(-1)), and better operational stability without compromising the rejection.
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| 41. |
- Lv, Yuexia, et al.
(author)
-
Wetting of polypropylene hollow fiber membrane contactors
- 2010
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 362:1-2, s. 444-452
-
Journal article (peer-reviewed)abstract
- Membrane wetting by absorbents leads to an Increase in mass transfer resistance and a deterioration in CO2 absorption performance during the membrane gas absorption process In order to better understand the wetting mechanism of membrane pores during their prolonged contact with adsorbents, polypropylene (PP) hollow fibers were Immersed in three different absorbents for up to 90 days Monoethanolamine, methyldiethanolamine, and deionized water were applied as absorbent solutions The characterization results of membrane samples confirm that the absorbent molecules diffuse into PP polymers during the exposure process, resulting in the swelling of the membranes The absorption-swelling wetting mechanism is proposed to explain observations made during the wetting process The strong reduction of contact angles indicates that the membrane surface hydrophobicity decreases remarkably during immersion due to membrane-absorbent interaction Membrane surface morphologies and surface roughness suffer from significant and complicated changes after immersing the membrane fibers in the absorbents. Immersion in an absorbent with a high surface tension results in small changes in membrane surface morphology. As indicated by the experimental results, improving membrane surface hydrophobicity may be an effective way of overcoming wetting problems.
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| 42. |
- Ma, Wenzhong, et al.
(author)
-
Membrane formation by thermally induced phase separation : materials, involved parameters, modeling, current efforts and future directions
- 2023
-
In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 669
-
Journal article (peer-reviewed)abstract
- Thermally-induced phase separation (TIPS) is one of the most popular methods considered for membrane preparation. Since its introduction by Castro in 1981, there has been significant progress in understanding, controlling, and implementing TIPS. This review provides a critical and integrative evaluation of the literature in this area that effectively defines the current state-of-the-art. It begins with an overview of the basic principles of TIPS and the used materials (polymers, diluents and additives) paying particular attention to the sustainability of the TIPS process. The subsequent sections examine the parameters affecting the outcome of TIPS technique, the role of mass transfer, and methods for modeling TIPS. This is followed by a discussion of current and potential applications of TIPS membranes. Finally, the review concludes with a discussion of likely future developments and prospects for the TIPS process.
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| 43. |
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| 44. |
- Manukyan, Levon, et al.
(author)
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Growth Media Filtration Using Nanocellulose-based Virus Removal Filter for Upstream Biopharmaceutical Processing
- 2019
-
In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 572, s. 464-474
-
Journal article (peer-reviewed)abstract
- The feasibility of using nanocellulose-based mille-feuille filter paper for upstream applications in serum-free growth media filtration, i.e. Dulbecco’s modified Eagle’s medium (DMEM) and Luria-Bertani medium (LBM), was tested. The filter performance with respect to F.174 bacteriophage (28nm) removal as a model small-size virus was characterized for filters of varying thicknesses, i.e. 11 and 33 mu m, at varying operating pressures, i.e. 1 and 3bar. The filters demonstrated generally good model small-size virus removal properties with LRV = 5, especially for 33 mu m filters. The 33 mu m filters were more robust and exhibited better virus removal and throughput properties than 11 mu m filters, although their flux was generally lower. The performance of the 33 and 11 mu m nanocellulose-based filter papers was further verified for upscaled bioporcessing by 10-fold increase in the loading volume. The results of the present work show that the 33 mu m nanocellulose-based filter paper could be an interesting alternative for large volume cell culture medium filtration during upstream bioprocessing.
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| 45. |
- Ng, Angie Qi Qi, et al.
(author)
-
Fouling behavior of protein in mixed solvent systems: A combined experimental and simulation study
- 2024
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In: Journal of Membrane Science. - 1873-3123 .- 0376-7388. ; 693
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Journal article (peer-reviewed)abstract
- Membrane fouling in organic solvent environments remains poorly explored despite its significance in chemical and pharmaceutical industries. This study uses molecular dynamics (MD) simulations and experiments to explore lysozyme fouling in water, as well as four organic solvent environments, namely, 30 % v/v and 50 % v/v isopropyl alcohol (IPA), and 30 % v/v and 50 % v/v dimethyl sulfoxide (DMSO). Experimentally, flux declines were least with IPA and worst with DMSO. Biased simulations indicate the worst fouling in DMSO is tied to the most attractive lysozyme-membrane energy in the presence of DMSO. However, the relative attractive energies for IPA and water do not agree with the relative flux declines, indicating other factors are more influential when the interaction energies are similar. To understand the gentler flux decline for IPA despite the more attractive lysozyme-membrane energy, radial distribution functions (RDFs) were obtained from unbiased simulations. Analyss of the water and solvent films around both the membrane and the lysozyme molecule reveal that the denser water film around both entities induced by the presence of IPA serves as a barrier for fouling and thus leads to less flux decline. The results underscore the complexity of fouling in organic solvent systems, cautioning against direct use of the understanding based on aqueous systems.
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| 46. |
- Nilsson, Mattias, et al.
(author)
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The influence of pH, salt and temperature on nanofiltration performance
- 2008
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 312:1-2, s. 97-106
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Journal article (peer-reviewed)abstract
- The influence of pH, KCl and temperature on the performance of an Alfa Laval NFT-50 nanofiltration membrane was evaluated by glucose and KCl retention measurements at constant flux. It was found that at constant temperature an increase in pH in the absence of KCl reduced the water permeability, and this was correlated to the electroviscous effect. The selectivity decreased with increasing KCl concentration and the decrease became more evident with increasing pH. The decrease in selectivity could be related to membrane swelling, and it appears that pH had no effect on swelling other than enhancing the effect of KCl. The influence of KCl and pH on membrane performance was evaluated as a function of temperature after reaching steady state at 50 °C. The degree of swelling was higher at 50 °C than at 20 °C, due to an increase in polymer flexibility with increasing temperature. The decrease in selectivity with increasing temperature was less for KCl than for glucose, showing that the charge effect was influenced less by temperature than diffusion through the membrane.
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| 47. |
- Nilsson, Mattias, et al.
(author)
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The influence of sodium chloride on mass transfer in a polyamide nanofiltration membrane at elevated temperatures
- 2006
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In: Journal of Membrane Science. - : Elsevier BV. - 0376-7388 .- 1873-3123. ; 280:1-2, s. 928-936
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Journal article (peer-reviewed)abstract
- The influence of temperature (20-50 degrees C) and NaCl on mass transfer of pure water and glucose solution (0.0055 M) using an Alfa Laval NFT-50 nanotiltration membrane has been investigated. Addition of 0.017 M NaCl(aq) increased the membrane permeability in comparison to measurements with pure water. Performing cyclic temperature variations using a membrane pre-treated with 0.20 M NaC](aq) caused the membrane permeability to decrease for each time a new maximum temperature was reached. After NaCl pre-treatment, the relative flux decline measured over 4 h was found to be greater for glucose than for water, and the rate of the flux decline for both water and glucose increased with temperature (20-50 degrees C). The permeability was found to be unaffected by the pressure if the membrane had previously been rinsed at a lower pressure but at a higher temperature. Changes in permeability due to the presence of NaCl could be related to interactions in the active polymer layer of the membrane. MgCl2 pre-treatment influenced the membrane permeability less that NaCl pre-treatment. (c) 2006 Elsevier B.V. All rights reserved.
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| 48. |
- Noor, Imtisal-e-, et al.
(author)
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Experimental investigation and techno-economic analysis of tetramethylammonium hydroxide removal from wastewater in nano-electronics manufacturing via membrane distillation
- 2019
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In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 579, s. 283-293
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Journal article (peer-reviewed)abstract
- In nano-electronics manufacturing, tetramethylammonium hydroxide (TMAH) is extensively used in the photo-lithography and etching processes, leading to a waste disposal issue. The present study focuses on TMAH wastewater treatment in nano-electronics industries by using membrane distillation technology. Actual TMAH wastewater samples were collected at imec, Belgium. An air gap membrane distillation bench unit was employed to perform the experiments for different operating conditions i.e., feed temperatures and flow rates. High quality water is recovered after reducing the TMAH concentration to 1 ppm and lowering the TOC to 0.8 ppm from 8 ppm. For the industrial scale TMAH wastewater treatment, industrial waste heat driven and district heating driven membrane distillation systems are designed and analyzed. It is determined that 14 GWh thermal energy is required annually to treat 20,000 m 3 of TMAH wastewater/year while considering 65 °C as the membrane distillation feed temperature. Expected unit water treatment cost is found as low as 16 $/m 3 of TMAH wastewater, roughly 80% lower than current disposal costs.
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| 49. |
- Owusu-Agyeman, Isaac, et al.
(author)
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Implications of humic acid, inorganic carbon and speciation on fluoride retention mechanisms in nanofiltration and reverse osmosis
- 2017
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In: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 528, s. 82-94
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Journal article (peer-reviewed)abstract
- The impact of pH and humic acid (HA) on the retention of fluoride (F) and inorganic carbon (IC) by nanofiltration (NF) and reverse osmosis (RO) membranes was determined. Synthetic waters were prepared using realistic ranges of F, IC and HA for carbonaceous waters found for example in the fluoride rich waters in Tanzania. These waters were filtered using NF270 and BW30 membranes to determine retention mechanisms. IC changes speciation with pH. The dominant species at pH < 6, 6-10 and > 10 are H2CO3, HCO3 and CO32- respectively. This results in changes in charge and size of the hydrated ion radius. The mechanism for IC retention by the NF270 and BW30 membranes are charge repulsion and size exclusion, respectively. F retention increases with pH. IC influenced F retention at pH > 10 where IC exists as divalent CO32- and is retained more easily than the monovalent F. HA enhances the retention of F by NF/RO membranes under certain conditions. The enhancement effect is more pronounced at neutral than at acidic pH and basic pH. The mechanism for the enhancement is attributed to the change in surface charge of the membranes by adsorption of HA. At high HA concentration the F retention enhancement is annulled by deposit formation on the membrane. The results obtained in this study indicate the complexity of retention in real surface- and ground waters that can alter significantly in pH as well as IC and HA content. The research is situated in the context of developing membrane technologies for autonomous systems in remote locations where water quality is variable and mechanisms of membrane performance are poorly understood.
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| 50. |
- Perdana, Indra, 1973, et al.
(author)
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Influence of NOx adsorbed species on component permeation through ZSM-5 membranes
- 2010
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In: Journal of Membrane Science. - : Elsevier BV. - 1873-3123 .- 0376-7388. ; 349:1-2, s. 83-89
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Journal article (peer-reviewed)abstract
- A thin ZSM-5 film was grown on an alpha-alumina support, resulting in a composite membrane. The membraneswere characterized by SEM and adsorption branch n-hexane/helium permporometry. In addition,the permeation of gas mixtures containing NO2, NO, N2 and argon was evaluated. The effect of temperatureand gas mixture composition on the component permeation and selectivity was investigated.It was found that NOx permeation through the ZSM-5 membrane was partially surface concentrationdependent and was thermally activated. However, transport by gas translational diffusion seemed todominate at the conditions studied. The presence of various NOx adsorbed species appeared to influencediffusion of NO2 in ZSM-5 and reduced transport of other inert and weakly adsorbed components overa wide temperature range (20–400◦C). Strongly adsorbed surface nitrate species formed in the presenceof gas phase NOx should be responsible for the reduced transport of these components at the elevatedtemperature. The findings are of interest for possible applications of ZSM-5 membranes for componentseparation at high temperature.
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