| 1. |
- 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.
|
|
| 2. |
- 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.
|
|
| 3. |
- 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.
|
|
| 4. |
- 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.
|
|
| 5. |
- 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.
|
|
| 6. |
- 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.
|
|
| 7. |
- 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.
|
|
| 8. |
- 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%.
|
|
| 9. |
- 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.
|
|
| 10. |
- 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.
|
|
