Chemical modifications to antifouling membranes are examined. Biomimetics is presented as an effective approach to modifying molecular filter membranes for greater efficiency.
Application of polymeric membranes for the adsorption of hazardous pollutants may lead to the development of next-generation reusable and portable water purification appliances. Membranes for ...membrane adsorption (MA) have the dual function of membrane filtration and adsorption to be very effective to remove trace amounts of pollutants such as cationic heavy metals, anionic phosphates and nitrates. In this review article, recent progresses in the development of MA membranes are surveyed. In addition, recent progresses in the development of advanced adsorbents such as nanoparticles are summarized, since they are potentially useful as fillers in the host membrane to enhance its performance. The future directions of R&D in this field are also shown in the conclusion section.
This review focuses on the development of polyamide (PA) thin film nanocomposite (TFN) membranes for various aqueous media-based separation processes such as nanofiltration, reverse osmosis and ...forward osmosis since the concept of TFN was introduced in year 2007. Although the total number of published TFN articles falls far short of the articles of the well-known thin film composite (TFC) membranes, its growth rate is significant, particularly since 2012. Generally, by incorporating an appropriate amount of nanofiller into a thin selective PA layer of a composite membrane, one could produce TFN membranes with enhanced separation characteristics as compared to the conventional TFC membrane. For certain cases, the resulting TFN membranes demonstrate not only excellent antifouling resistance and/or greater antibacterial effect, but also possibly overcome the trade-off effect between water permeability and solute selectivity. Furthermore, this review attempts to give the readers insights into the difficulties of incorporating inorganic nanomaterials into the organic PA layer whose thickness usually falls in a range of several-hundred nanometers. It is also intended to show new possible approaches to overcome these challenges in TFN membrane fabrication.
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•Comprehensive review on the development of TFN membrane for water treatment.•Potential of TFN membrane in overcoming permeability/selectivity trade-off effect.•Nanofiller characteristics/amount and IP condition that affect TFN properties.•Innovative approaches to overcome TFN fabrication challenges.
A facile route for the in situ surface modification and mechanical strength-enhancement of electrospun nanofibers is described. Blends of a host hydrophilic polymer, polysulfone (PSF), and small ...quantities of a fluorinated polyurethane additive (FPA) up to 6 wt% in the PSF blend were considered. During electrospinning, this additive undergoes spontaneous surface segregation resulting in nanofibers with an improved hydrophobic character attributed mainly to the detected fluorine-rich surface and enhanced mechanical properties. We report the effects of the fluorinated additive content in the blend on the morphological and structural characteristics of the electrospun nanofibrous mats (ENMs) including their inter-fiber space and void volume fraction. ENMs with a superhydrophobic surface could be prepared using at least 3 wt% FPA in the PSF blend. The ENMs were tested in desalination by membrane distillation (MD) and competitive permeate fluxes as high as 53.8 kg/m2h, with stable low permeate electrical conductivities (<5.1 μS/cm), were achieved for the ENM prepared with 4.5 wt% FPA in the PSF blend, when the feed was 30 g/L NaCl aqueous solution and the transmembrane temperature difference was 60 °C, without any inter-fiber space wetting being detected.
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•Surface modification of polysulfone (PSF) nanofiber by surface segregation.•Fluorine enrichment of electrospun PSF nanofiber surface and superhydrophobicity.•Use of small amount of fluorinated polyurethane active additive (FPA).•Suitable characteristics for desalination by direct contact membrane distillation.•Competitive and stable permeate fluxes without interfiber space wetting were achieved.
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•Modifications on PSf substrate of TFC membrane using TiO2 nanoparticles.•Performances of PSf substrate were improved upon addition of TiO2 nanoparticles.•TFN FO membrane with small S ...value and minimum ICP was able to produce.
In this work, polysulfone (PSf)–titanium dioxide (TiO2) nanocomposite substrates were prepared by incorporating different amounts of TiO2 nanoparticles (ranging from zero to 1wt%) into PSf matrix. The nanocomposite substrates so prepared were then characterized with respect to hydrophilicity, overall porosity, surface roughness and cross-sectional morphology. It was found that both hydrophilicity and porosity of the substrate were increased upon addition of TiO2. In addition, long finger-like structures were developed by increasing the TiO2 loading, leading to water permeability enhancement. In order to fabricate thin film nanocomposite (TFN) membranes for forward osmosis (FO) application, a thin polyamide layer was formed by interfacial polymerization of 1,3-phenylendiamine and 1,3,5-benzenetricarbonyl trichloride on the top surface of PSf–TiO2 nanocomposite substrates. Under the conditions for FO performance evaluation (10mM NaCl concentration in feed solution, 0.5 and 2.0M NaCl concentration in draw solution, and both active layer facing the feed solution (AL–FS) and active layer facing the draw solution (AL–DS) orientations), the TFN membrane prepared using PSf substrate embedded with 0.5wt% TiO2 nanoparticles (denoted as TFN0.5) exhibited the most promising results by showing high water permeability and low reverse solute flux. In comparison with control TFC membrane, the water flux of TFN0.5 membrane was improved by 86–93%, depending on the membrane orientation and draw solution concentration. The increase in water permeability can be attributed to decrease in structural parameter which resulted in decreased internal concentration polarization (ICP). Although further increase in TiO2 nanoparticles loading to 0.75 and 1wt% could result in higher water permeability, their FO performances were compromised by a significant increase in reverse solute flux. Based on the results obtained in this work, it can be concluded that adding an appropriate amount of TiO2 nanoparticles into PSf substrate could potentially improve the performance of TFC membrane during FO applications.
Access to clean water resource continues to be the most urgent and pressing global issue where hiking economic and ecological needs have urged for more water-efficient technologies. Membrane-based ...separations for desalination are playing an increasingly important role to provide adequate water resources of desirable quality for a wide spectrum of designated applications. The engagement of multidisciplinary research areas into the commercial membrane and membrane systems offers an opportunity to refine and optimise current techniques as well as provides new insight and novel methods of purifying water. The advancement of material science and engineering reveals the potentials to solve real-world practical problems and heighten the current technologies. This review highlights some of the latest notable achievements of novel advanced membrane materials and emerging membrane processes for water solution. The unique characteristics of advanced membranes and emerging membrane processes in leading the state-of-the-art desalination are presented. Lastly, the future directions for research, development and commercialization of membrane and membrane processes are critically discussed. It is expected that, the promising and well-adapted characteristics possessed by the novel membranes and advanced membrane processes can provide meaningful inspiration for breakthrough technologies and solutions where soon they will be translated into exploitable innovations in industries.
•Current trends of membrane materials for desalination•Emerging membrane-based desalination processes•Challenges and future outlook of novel membranes and membrane processes
This paper provides a review on the recent development of thin film composite (TFC) membrane, which has received increasing attention in the field of water desalination process. The development of ...new thin films and substrates, and the effect of additives are mostly focused in this review. In particular, nanotechnology has shown its impact on the development of TFC membranes by incorporating nanoparticles and nanofibers in the substrate as well as in the top thin film. The search for novel monomers and novel fabrication methods of thin film, modification of substrate, and optimization of operational conditions is also the topic of this review article. It still remains a challenge to produce high impact TFC membranes with antifouling and biofouling properties, chemical resistance, improved mechanical strength and thermal stability. For this purpose, further insights into the phase inversion and interfacial polymerization processes are necessary. Currently, it seems that there is no end in the near future for the further development of TFC membranes, which will be followed by the expansion of the scope of their applications in various chemical and biochemical industrial sectors.
•A review on the recent development of thin film composite (TFC) membrane•Emerging nanotechnology for advanced membrane preparation•Future directions of TFC membrane development
In this work, polysulfone (PSf) substrates with different properties were made by varying the polymer concentration in the dope solution in the range 12–20wt.%. Polyamide (PA) thin layers were then ...formed via interfacial polymerization between piperazine and trimethylchloride over the PSf substrates. Both top PA thin layers and bottom PSf substrates were characterized with respect to physicochemical properties, structural morphology, and water flux/salt rejection to investigate the influence of substrate properties on the characteristics of PA thin layers. Physical properties of the PA layers were reported to be altered using different PSf substrate properties and were in good agreement with the change in water flux. From the FESEM pictures, it is found that the thickness of PA layer increased as the surface pore size of support membrane decreased. The change in the membrane structural properties in particular pore size is found to portray significant contribution to the changes of formed PA layer. Interestingly, only slight changes on Na2SO4 and MgSO4 salt rejection were reported on any TFC membranes. Considering both water permeability and salt rejection rate, the best performing TFC membrane produced in this work was the membrane made over substrate of 15wt.% PSf concentration.
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•Properties of PSf substrate membranes were fundamentally investigated.•Pore size and porosity of substrate portray major role in the changes of PA layer.•TFC NF membrane made of PSf 15wt.% substrate produced the best performance.
▶ The performance studies of the mixed matrix membranes for gas separation were critically reviewed. ▶ The methods for avoiding non-ideal interfacial defects were presented. ▶ The permeation models ...for the mixed matrix gas separation membranes were discussed in details. ▶ The future direction of research and development to fully exploit the potential usage of MMM was shown.
Development of polymeric gas separation membranes is one of the fastest growing branches of membrane technology. However, polymeric materials are somewhat deficient in meeting the requirements of current membrane technology. Mixed matrix membrane (MMM), comprising rigid permeable or impermeable particles, such as zeolites, carbon molecular sieves, silica and carbon nanotubes, dispersed in a continuous polymeric matrix presents an interesting approach for improving the separation properties of polymeric membranes. In this approach, using properties of both the organic and inorganic phase, a membrane with good permeability, selectivity, mechanical strength, and thermal, chemical stability and processibility can be prepared. In this paper the performance studies of MMM for gas separation were critically reviewed. In addition, the materials selection and the preparation techniques of MMM were also discussed. Methodology in improving the interface defects in the MMM and its effect on the separation performance have also been reviewed. The models for predicting the performance of MMM for gas separation have been discussed in details and the future direction of research and development to fully exploit the potential usage of MMM was shown.
The development in the area of surface modification of polymeric synthetic membranes since 2000 is reviewed. Many patents, articles, and reviews have been written on the development in the area of ...surface modification of polymeric synthetic membranes subjected to RO, UF, NF, gas separation (GS), and biomedical applications, mainly since 2000, but recently more attention has been given to the modification of their surfaces to obtain desirable results. In particular, most emphasis has been given to plasma treatment, grafting of polymers on the surface, and modifying the surfaces by adding SMMs (surface-modifying molecules). New additives are synthesized to make the polymeric membrane surfaces either to be more hydrophilic or hydrophobic, aimed at improvement in selectivity and permeability of the membranes for GS, NF, and RO. Improvement in antifouling by surface modification is also a popular topic in the membrane industries. In the last 8 years, tremendous research efforts have been made on the development of antifouling membranes.
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