| 1. |
- He, Ting, et al.
(författare)
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Poly(vinylidene fluoride) (PVDF) membrane fabrication with an ionic liquid via non-solvent thermally induced phase separation (N-TIPs)
- 2022
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Ingår i: Applied water science. - : Springer. - 2190-5487 .- 2190-5495. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was the first time successfully utilized as single solvent in preparing the PVDF membrane with a good performance by N-TIPs method. The effects of quenching temperature and hydrophilic additive content on the morphology, permeability, and strength of the membranes were studied. All the prepared PVDF membranes were proved to be a pure β phase by FTIR and XRD, possessing a narrow pore size distribution. By adjusting quenching temperature and additive content, membranes with a flux of 383.2 L/m2 h and concentrated pore diameter of 26 nm obtained.
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| 2. |
- Ismail, Norafiqah, et al.
(författare)
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Dibasic esters as green solvents for PVDF membrane preparation
- 2023
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Ingår i: Green Chemistry. - : Royal Society of Chemistry. - 1463-9262 .- 1463-9270. ; 25:18, s. 7259-7272
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Tidskriftsartikel (refereegranskat)abstract
- Solvent toxicity is a major barrier to sustainable fabrication of polymeric membranes. This study introduces three dibasic esters (DBEs) as alternative membrane fabrication solvents that are biodegradable, non-carcinogenic, non-corrosive, and non-hazardous. The use of DBEs in fabrication processes shifts the monotectic point in the phase diagram of PVDF/solvent systems towards higher polymer concentrations, enabling membrane formation by liquid–liquid phase inversion to produce a bicontinuous structure that confers outstanding performance. The best-performing membrane prepared in this way had an exceptional flux of 42.40 kg m−2 h−1 and a high rejection rate (>99%) in the decontamination of synthetic nuclear wastewater. Compared to membranes prepared previously using toxic and non-toxic solvents, membranes fabricated in DBEs exhibited superior mechanical performance due to their bicontinuous structure, which effectively distributes external forces throughout the membrane. Moreover, DBEs are cheaper than toxic conventional solvents and are readily available in bulk, making them attractive options for industrial-scale membrane production.
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| 3. |
- Ismail, Norafiqah, et al.
(författare)
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Experimental and theoretical studies on the formation of pure β-phase polymorphs during fabrication of polyvinylidene fluoride membranes by cyclic carbonate solvents
- 2021
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Ingår i: Green Chemistry. - : Royal Society of Chemistry. - 1463-9262 .- 1463-9270. ; 23:5, s. 2130-2147
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Tidskriftsartikel (refereegranskat)abstract
- The use of highly toxic solvents presents significant risks to both the environment and human health. Therefore, the adoption of green solvents will be crucial for achieving sustainable membrane production. This work reports the use of inexpensive environmentally friendly biobased and biodegradable cyclic carbonate solvents, namely ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), to fabricate polyvinylidene fluoride (PVDF) membranes. The solvent dependence of the phase inversion mechanisms, morphology, crystalline structures, and polymorphism of the prepared PVDF membranes were investigated. Polymorph analysis revealed that membrane fabrication in EC or PC yielded exclusively the β-phase product, whereas PVDF membrane fabrication in BC yielded a mixture of α and β phase material. The mechanism of β-phase formation was investigated using molecular dynamics simulation and shown to depend on the extent of hydrogen bonding at the polymer–solvent interface. The PVDF membrane formed in EC exhibited the highest porosity and pure water permeability, and was therefore tested in direct contact membrane distillation (DCMD), exhibiting promising results in terms of permeate flux and salt rejection. These results suggest that large-scale production of piezoelectric PVDF membranes using green solvents should be practically feasible.
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| 4. |
- Ismail, Norafiqah, et al.
(författare)
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Non-ionic deep eutectic solvents for membrane formation
- 2022
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Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 646
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Tidskriftsartikel (refereegranskat)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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| 5. |
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| 6. |
- Ma, Wenzhong, et al.
(författare)
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Membrane formation by thermally induced phase separation : materials, involved parameters, modeling, current efforts and future directions
- 2023
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Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 669
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Pan, Jun, et al.
(författare)
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Enhanced anti-wetted PVDF membrane for pulping RO brine treatment by vacuum membrane distillation
- 2022
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Ingår i: Desalination. - : Elsevier. - 0011-9164 .- 1873-4464. ; 526
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Tidskriftsartikel (refereegranskat)abstract
- Large amounts of lignin, hemicellulose, organic matter and inorganic salts are present in pulping and papermaking wastewater. Therefore, the treatment and discharge of pulping wastewater are important issues. We have designed and developed the world's first zero liquid discharge (ZLD) system for it based on pretreatment-membrane-evaporative crystallization integrated technologies. However, for the treatment of high salt reverse osmosis (RO) brine, there are still challenges that need to be addressed. In this work, the feasibility of using a membrane distillation crystallization (MDC) process to treat high saline RO brine was investigated. Two different coating materials, Hyflon AD 40H and perfluoropolyether (PFPE), were applied to improve the membrane surface hydrophobicity for stable and efficient performance. After modification, the water contact angle was up to 138.4o and 157.7o for Hyflon/polyvinylidene fluoride (PVDF) and PFPE/PVDF composite membranes, respectively. Moreover, the PFPE/PVDF membrane showed a higher repellency toward RO brine, which is better for the following MDC treatment. During the MDC progress using composite PFPE/PVDF membranes, the salt crystals precipitated and gradually accumulated. More importantly, the final NaCl purity can be up to 94%. Therefore, it is hopeful to improve of the existing ZLD system by MDC operation.
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| 8. |
- Pan, Jun, et al.
(författare)
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Poly(vinylidene fluoride-co-hexafluoro propylene) membranes prepared via thermally induced phase separation and application in direct contact membrane distillation
- 2022
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Ingår i: Frontiers of Chemical Science and Engineering. - : Springer. - 2095-0179 .- 2095-0187. ; 16, s. 720-730
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Tidskriftsartikel (refereegranskat)abstract
- A non-toxic and environmentally safe diluent, acetyl tributyl citrate, was employed to prepare poly (vinylidene fluoride)-co-hexafluoropropylene membranes via thermally induced phase separation. Effects of the polymer concentration on the phase diagram, membrane morphology, hydrophobicity, pore size, porosity and mechanical properties (tensile stress and elongation at break) were investigated. The results showed that the pore size and porosity tended to decrease with increasing polymer concentration, whereas the contact angle, liquid entry pressure and mechanical properties showed the opposite trend. In direct contact membrane distillation operation with 3.5 wt-% sodium chloride solution as the feed solution, the prepared membranes performed high salt rejection (> 99.9%). Furthermore, the prepared membranes retained excellent performance in long-term stability tests regarding the permeate flux and salt rejection. [Figure not available: see fulltext.]
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| 9. |
- Wang, Qian, et al.
(författare)
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Annealing of grain-like poly (vinylidene fluoride-trifluoroethylene) membranes with a single-crystalline electroactive phase and high anti-fouling activity
- 2022
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Ingår i: Journal of Membrane Science. - : Elsevier. - 0376-7388 .- 1873-3123. ; 644
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Tidskriftsartikel (refereegranskat)abstract
- Electroactive membranes are attracting attention due to their piezo-, pyro-, and ferro-electric properties. Here we report the fabrication of electroactive membranes from poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), i.e. co-polymers of vinylidene fluoride and trifluoroethylene. A new P(VDF-TrFE)/Polyvinylpyrrolidone (PVP)/Dimethylacetamide (DMAc)/water system was used to tailor the membranes’ structure. Since hot treatment in the air could induce defect on membrane structure (i.e., fracture, shrinkage, and rolling), the annealing was conducted in the glycerin. Thanks to the high boiling point and moderate surface tension of glycerin, the integrity of P(VDF-TrFE) membranes was preserved during the annealing process. X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy experiments revealed that the relative abundance of the β–crystalline phase increased with the annealing temperature when the latter was above the Curie temperature. P(VDF-TrFE) membranes annealed at 130 °C exhibited high crystallinity with grain-like surface, which resulted from multiple stacks of edge-on lamellae, and possessed excellent physicochemical properties of filtration. The anti-fouling performance of pristine and annealed P(VDF-TrFE) membranes was tested by dead-end filtration with a 13.5 mg/L humic acid (HA) solution. Annealed P(VDF-TrFE) membranes achieved greater fluxes and had superior anti-fouling properties, which was attributed to the weaker hydrophobic attraction between HA and the aligned β–phase crystals. This work provides a facile method for designing highly crystalline P(VDF-TrFE) membranes with potential applications in filtration systems, smart wearable devices, and medicine.
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| 10. |
- Zhou, Zhuang, et al.
(författare)
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Thermally induced phase separation
- 2024
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Ingår i: Polymeric membrane formation by phase inversion. - : Elsevier. - 9780323956284 - 9780323956291 ; , s. 37-82
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Thermally induced phase separation (TIPS) stands as one of the most widely employed methods for preparing polymeric membranes in industrial and academic settings. This chapter aims to provide comprehensive background information on the TIPS method. First, the mechanism of phase inversion from both thermodynamic and kinetic perspectives will be presented. Subsequently, the impact of preparation parameters on membrane performance will be analyzed. The chapter also emphasizes the crucial role of mass transfer in the TIPS process. Moreover, the practical application of the membranes prepared using the TIPS method will be highlighted. Finally, in the concluding section, a summary and future perspectives will be provided.
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