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Jeffrey R Mccutcheon - One of the best experts on this subject based on the ideXlab platform.
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proper accounting of mass transfer resistances in forward osmosis improving the accuracy of model predictions of structural parameter
Journal of Membrane Science, 2015Co-Authors: Jason T. Arena, Jeffrey R MccutcheonAbstract:Abstract This work demonstrates a more accurate method for calculating structural parameter ( S ) of asymmetric osmotic membranes using experimental data and a theoretical flux model which encapsulates all significant boundary layer phenomena. External boundary layer effects on the porous side of the membrane have been neglected in many current models. In these models, external Concentration Polarization (ECP) effects get combined with Internal Concentration Polarization (ICP), resulting in inflated S values. In this study, we proposed a mathematical flux model in which ECP effects are accounted for, so that S can be more accurately measured. This model considered the in-series resistances for solute transport based on intrinsic properties of the membrane, as well as boundary layers at membrane surfaces and within the support layer. We therefore introduced new equations to define total resistance to solute transport and reflection coefficient of membranes in FO. The results indicate that ICP is less severe than previously predicted and that cross-flow velocity, temperature and Concentration of the draw and the feed solutions impact both external and Internal Concentration Polarization. Our calculations surprisingly show that changes in cross-flow velocity impact Internal Concentration Polarization due to induced mixing within the support layer. Also, we suggest that it is critical to consider the “ residence time ” of solutes in the vicinity of the selective layer when determining the membrane selectivity.
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Characterization of Thin Film Composite Membranes Using Porosimetry and X-Ray Microscopy
Microscopy and Microanalysis, 2013Co-Authors: Seetha S Manickam, Jeff Gelb, Jeffrey R MccutcheonAbstract:Engineered osmosis is a membrane-based technology employing osmotic pressure gradients to desalinate water (forward osmosis, FO) and produce power (pressure retarded osmosis, PRO). Internal Concentration Polarization (ICP) is one of the most important phenomena limiting commercialization of EO. Structural characteristics of the membrane greatly influence the ICP phenomena and are expressed using the structural parameter, S as
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novel hydrophilic nylon 6 6 microfiltration membrane supported thin film composite membranes for engineered osmosis
Journal of Membrane Science, 2013Co-Authors: Liwei Huang, Mark T Meyering, Thomas J Hamlin, Jeffrey R MccutcheonAbstract:Abstract Previous investigations of engineered osmosis (EO) concluded that hydrophobic support layers of thin film composite membrane causes severe Internal Concentration Polarization due to incomplete wetting. Incomplete wetting reduces the effective porosity of the support, inhibiting mass transport and thus water flux. In this study, novel thin film composite membranes were developed which consist of a poly(piperazinamide) or polyamide selective layer formed by interfacial polymerization on top of a nylon 6,6 microfiltration membrane support. This intrinsically hydrophilic support was used to increase the “wetted porosity” and to mitigate Internal Concentration Polarization. Reverse osmosis tests showed that the permselectivity of our best poly(piperazinamide) and polyamide thin film composite membranes approached those of a commercial nanofiltration and a commercial reverse osmosis membrane, respectively. The osmotic flux performance of the new polyamide thin film composite membrane showed matched water flux, 10 fold lower salt flux and 8–28 fold lower specific salt flux than the standard commercial cellulose triacetate forward osmosis membrane from Hydration Technology Innovations™. The relatively good performance in osmotic flux tests of our thin film composite membranes was directly related to the high permselectivity of the selective layers coupled with the hydrophilicity of the nylon 6,6 support. These results suggest that these nylon 6,6 supported thin film composite membranes may enable applications like forward osmosis or pressure retarded osmosis.
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surface modification of thin film composite membrane support layers with polydopamine enabling use of reverse osmosis membranes in pressure retarded osmosis
Journal of Membrane Science, 2011Co-Authors: Jason T. Arena, Bryan D Mccloskey, Benny D. Freeman, Jeffrey R MccutcheonAbstract:Abstract Previous investigations of forward osmosis and pressure retarded osmosis identified asymmetric membrane support layer hydrophilicity as critical to obtain high water flux. In this study, the support layers of two commercially available thin film composite reverse osmosis membranes were modified to enhance their hydrophilicity. The membrane support layers were coated with polydopamine, a novel bio-inspired hydrophilic polymer. This resulted in increased hydrophilicity and a corresponding increase in ‘wetted porosity’ and reduced Internal Concentration Polarization. The modified membranes were then characterized for contact angle, salt rejection, hydraulic permeability, salt flux, and osmotic flux. The results were promising, indicating that the modified reverse osmosis membranes exhibited an eight to fifteen fold increase in flux performance under test conditions when compared to baseline control data. This modification method, which is scalable, has the potential to enable the use of existing thin film composite membranes for all engineered osmosis applications.
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modeling water flux in forward osmosis implications for improved membrane design
Aiche Journal, 2007Co-Authors: Jeffrey R Mccutcheon, Menachem ElimelechAbstract:Osmotically-driven membrane processes, such as forward osmosis and pressure retarded osmosis, operate on the principle of osmotic transport of water across a semipermeable membrane from a dilute feed solution into a concentrated draw solution. The major hindrance to permeate water flux performance is the prevalence of Concentration Polarization on both sides of the membrane. This article evaluates the external and Internal boundary layers, which decrease the effective osmotic driving force. By modeling permeate flux performance, the role that feed and draw Concentrations, membrane orientation, and membrane structural properties play in overall permeate flux performance are elucidated and linked to prevalence of external and Internal Concentration Polarization. External Concentration Polarization is found to play a significant role in the reduction of driving force, though Internal Concentration Polarization has a far more pronounced effect for the chosen system conditions. Reduction of Internal Concentration Polarization by way of membrane modification was found to improve the predicted flux performance significantly, suggesting that alteration of membrane design will lead to improved performance of osmotically driven membrane processes. 2007 American Institute of Chemical Engineers AIChE J, 53: 1736–1744, 2007
Menachem Elimelech - One of the best experts on this subject based on the ideXlab platform.
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Sub-1 μm Free-Standing Symmetric Membrane for Osmotic Separations
Environmental Science & Technology Letters, 2019Co-Authors: Wei Cheng, Xuan Zhang, Menachem ElimelechAbstract:Desalination membranes have an asymmetric structure and thus experience severe Internal Concentration Polarization (ICP) in osmotic separations, such as desalination and water purification. ICP sub...
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Concentration and Recovery of Dyes from Textile Wastewater Using a Self-Standing, Support-Free Forward Osmosis Membrane
Environmental Science & Technology, 2019Co-Authors: Xi Wang, Xuan Zhang, Lianjun Wang, Wei Cheng, Cassandra J. Porter, Menachem ElimelechAbstract:Forward osmosis (FO) can potentially treat textile wastewaters with less fouling than pressure-driven membrane processes such as reverse osmosis and nanofiltration. However, conventional FO membranes with asymmetric architecture experience severe flux decline caused by Internal Concentration Polarization and fouling as dye molecules accumulate on the membrane surface. In this study, we present a new strategy for concentrating dye by using a self-standing, support-free FO membrane with a symmetric structure. The membrane was fabricated by a facile solution-casting approach based on a poly(triazole-co-oxadiazole-co-hydrazine) (PTAODH) skeleton. Due to its dense architecture, ultrasmooth surface, and high negative surface charge, the PTAODH membrane exhibits excellent FO performance with minimal fouling, low reverse salt flux, and negligible dye passage to the draw solution side. Cleaning with a 40% alcohol solution, after achieving a Concentration factor of ∼10, resulted in high flux recovery ratio (98.7%) ...
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A Self-Standing, Support-Free Membrane for Forward Osmosis with No Internal Concentration Polarization
Environmental Science & Technology Letters, 2018Co-Authors: Vasiliki Karanikola, Xuan Zhang, Lianjun Wang, Menachem ElimelechAbstract:Conventional asymmetric or thin-film composite forward osmosis (FO) membranes suffer from severe Internal Concentration Polarization, which significantly hinders process performance and practical applications. Here we report the synthesis of the COOH-derived polyoxadiazole copolymer for the fabrication of a self-standing selective thin film without a support layer. The thickness of the membrane was controlled at merely a few micrometers to achieve a high rate of rejection of the Na2SO4 draw solution, while maintaining acceptable water permeability. Because of the symmetric architecture, the membrane exhibited excellent and identical FO performance at both of its sides. The structural parameter of the fabricated membranes was zero because of the absence of Internal Concentration Polarization in the symmetric FO membranes. Our results highlight the potential of support-free membranes for the further development of FO technology.
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A Self-Standing, Support-Free Membrane for Forward Osmosis with No Internal Concentration Polarization
2018Co-Authors: Vasiliki Karanikola, Xuan Zhang, Lianjun Wang, Menachem ElimelechAbstract:Conventional asymmetric or thin-film composite forward osmosis (FO) membranes suffer from severe Internal Concentration Polarization, which significantly hinders process performance and practical applications. Here we report the synthesis of the COOH-derived polyoxadiazole copolymer for the fabrication of a self-standing selective thin film without a support layer. The thickness of the membrane was controlled at merely a few micrometers to achieve a high rate of rejection of the Na2SO4 draw solution, while maintaining acceptable water permeability. Because of the symmetric architecture, the membrane exhibited excellent and identical FO performance at both of its sides. The structural parameter of the fabricated membranes was zero because of the absence of Internal Concentration Polarization in the symmetric FO membranes. Our results highlight the potential of support-free membranes for the further development of FO technology
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Module-Scale Analysis of Pressure Retarded Osmosis: Performance Limitations and Implications for Full-Scale Operation
Environmental Science & Technology, 2014Co-Authors: Anthony P. Straub, Shihong Lin, Menachem ElimelechAbstract:We investigate the performance of pressure retarded osmosis (PRO) at the module scale, accounting for the detrimental effects of reverse salt flux, Internal Concentration Polarization, and external Concentration Polarization. Our analysis offers insights on optimization of three critical operation and design parameters—applied hydraulic pressure, initial feed flow rate fraction, and membrane area—to maximize the specific energy and power density extractable in the system. For co- and counter-current flow modules, we determine that appropriate selection of the membrane area is critical to obtain a high specific energy. Furthermore, we find that the optimal operating conditions in a realistic module can be reasonably approximated using established optima for an ideal system (i.e., an applied hydraulic pressure equal to approximately half the osmotic pressure difference and an initial feed flow rate fraction that provides equal amounts of feed and draw solutions). For a system in counter-current operation wi...
Chuyang Y Tang - One of the best experts on this subject based on the ideXlab platform.
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Polydopamine coating on a thin film composite forward osmosis membrane for enhanced mass transport and antifouling performance
Journal of Membrane Science, 2018Co-Authors: Hao Guo, Zhikan Yao, Xiaohua Ma, Jianqiang Wang, Zhe Yang, Chuyang Y TangAbstract:We applied a polydopamine (PDA) coating on a thin film composite (TFC) forward osmosis (FO) membrane and investigated the effects of coating on FO mass transport and antifouling behavior. The PDA coating significantly improved membrane surface hydrophilicity as well as reduced membrane surface roughness. Using a short PDA coating duration of 0.5 h, the coated membrane TFC-C0.5 achieved enhanced FO water flux and reduced reverse solute diffusion simultaneously. The reduced reverse solute diffusion can be attributed to the enhanced membrane selectivity: TFC-C0.5 had better rejection and similar water permeability compared to the original TFC membrane. This reduction in reverse solute diffusion further reduced the Internal Concentration Polarization inside the coated membrane, leading to an enhanced FO water flux. Nevertheless, longer PDA coating duration of 1–4 h resulted in reduced FO water flux due to the significantly increased hydraulic resistance of the coated membranes. The PDA coated membrane TFC-C0.5 also presented an improved antifouling performance compared to the control membrane using alginate as a model foulant. Our results reveal the great room for the development of effective coating materials in FO: a well-designed coating with high selectivity and low hydraulic resistance can improve solute rejection, reduce reverse solute diffusion, mitigate Internal Concentration Polarization and enhance FO water flux in addition to control fouling. Such unprecedented opportunities break the traditional trade-off between water flux and antifouling performance when coating pressure driven reverse osmosis membranes.
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Novel Membranes and Membrane Materials
Membrane-Based Salinity Gradient Processes for Water Treatment and Power Generation, 2018Co-Authors: Zhe Yang, Chuyang Y TangAbstract:Abstract In this chapter, the state-of-the-art membrane materials used for forward osmosis (FO) and pressure-retarded osmosis (PRO) processes are presented. Conventional polymeric membranes, such as cellulose triacetate and thin-film composite membranes, are briefly introduced. Some of the major drawbacks for these conventional polymeric membranes include Internal Concentration Polarization (ICP), low water flux, high reverse solute flux, and strong fouling tendency. At the same time, many novel membrane materials and structures have emerged in the recent membrane literature. Some notable examples include mixed matrix and nanocomposite structure for enhancing membrane permeability and reducing ICP and the use of aquaporins and carbon-based materials (e.g., carbon nanotubes and graphene oxides) to improve membrane separation properties. These techniques provide promising new dimensions for designing next generation FO/PRO membranes.
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Ultrasound-assisted forward osmosis for mitigating Internal Concentration Polarization
Journal of Membrane Science, 2017Co-Authors: Juha Heikkinen, Hanna Kyllönen, Eliisa Järvelä, Antti Grönroos, Chuyang Y TangAbstract:Abstract Internal Concentration Polarization (ICP) severely limits water flux performance in forward osmosis (FO). We investigated the use of ultrasound to mitigate ICP. Various parameters affecting the performance of the novel ultrasonically-assisted FO were studied, such as ultrasonic frequency and constant versus pulsed operation. With either deionized water or polyphenolic tannin solution as the feed and sodium sulphate as the draw solution, the water flux was nearly doubled for a thin film composite FO membrane upon the application of a 20 kHz ultrasound, with stronger enhancement achieved when the ultrasound was applied to the support layer of the membrane. High frequencies of 573 and 1136 kHz had much weaker effects. Pulsed application of ultrasound can significantly reduce the energy consumption of sonication. For the first time, the current study provides compelling evidence that ultrasonic vibrations applied to porous support structure of an FO membrane is highly effective in mitigating ICP.
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metal organic framework based porous matrix membranes for improving mass transfer in forward osmosis membranes
Journal of Membrane Science, 2015Co-Authors: Chuyang Y TangAbstract:Abstract Internal Concentration Polarization (ICP) in substrate layer is one of the most critical bottlenecks of the forward osmosis (FO) process. In this study, we explored the use of metal–organic frameworks (MOFs) as a removable filler to prepare MOF-based porous matrix membranes (PMMs) for improving the mass transfer in the FO substrates and hence controlling the ICP. MOF-based porous matrix substrates (PMSs) with three different types of MOFs were prepared via phase inversion by adding MOF particles into the polyacrylonitrile (PAN) dope solution. A thin selective layer was prepared using a layer-by-layer (LbL) deposition method on top of the porous matrix FO substrate. The bond dissociation energy (BDE) between metal ions and organic linker of MOF particles played an important role for the selection of fillers of PMMs. For MOF particles with lower BDE (
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Metal–organic framework-based porous matrix membranes for improving mass transfer in forward osmosis membranes
Journal of Membrane Science, 2015Co-Authors: Jian-yuan Lee, Qianhong She, Fengwei Huo, Chuyang Y TangAbstract:Abstract Internal Concentration Polarization (ICP) in substrate layer is one of the most critical bottlenecks of the forward osmosis (FO) process. In this study, we explored the use of metal–organic frameworks (MOFs) as a removable filler to prepare MOF-based porous matrix membranes (PMMs) for improving the mass transfer in the FO substrates and hence controlling the ICP. MOF-based porous matrix substrates (PMSs) with three different types of MOFs were prepared via phase inversion by adding MOF particles into the polyacrylonitrile (PAN) dope solution. A thin selective layer was prepared using a layer-by-layer (LbL) deposition method on top of the porous matrix FO substrate. The bond dissociation energy (BDE) between metal ions and organic linker of MOF particles played an important role for the selection of fillers of PMMs. For MOF particles with lower BDE (
Tai-shung Chung - One of the best experts on this subject based on the ideXlab platform.
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Thin-film composite (TFC) hollow fiber membrane with double-polyamide active layers for Internal Concentration Polarization and fouling mitigation in osmotic processes
Journal of Membrane Science, 2017Co-Authors: Gang Han, Zhen Lei Cheng, Tai-shung ChungAbstract:Abstract Internal Concentration Polarization (ICP) and severe irreversible fouling occurring within the porous and tortuous substrates of the forward osmosis (FO) and pressure retarded osmosis (PRO) membranes have significantly hidden their applications for water purification and osmotic power generation. This study experimentally demonstrates that designing a double-skin structure in FO and PRO membranes can effectively control ICP and their fouling propensity. Thin-film composite (TFC) hollow fiber membranes consist of an inner polyamide selective skin and an outer polyamide sealing layer were successfully fabricated by double interfacial polymerizations on a tailored polyethersulfone (PES) fiber substrate (termed as d TFC-PES). Due to the outstanding rejection of the outer polyamide sealing layer, the penetration of inorganic salts and foulants into the substrate is sufficiently blocked. As a result, not only ICP and fouling inside the membrane are effectively minimized, but also sustainable FO and PRO performances are achieved. By using real wastewater contains multiple inorganic salts and organic foulants as the feed, the d TFC-PES membrane shows a quite low flux decline of 29% in FO operations under the PRO mode at an ultrahigh feed recovery of 80%. Under PRO tests for power generation, the membrane power density slightly drops to 90.8% of the initial value after a 12-h test at Δ P =15 bar. In addition, since foulants are primarily accumulated on the surface of the polyamide sealing layer, physically flushing the fouled membrane surface by either freshwater or commercial cleaner Genesol 704 can efficiently restore the water flux back to its initial level with a recovery rate of 87% or 98%, respectively. This study may offer useful insights and meaningful strategies for the development of effective antifouling FO and PRO membranes.
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thin film composite forward osmosis membranes with enhanced Internal osmotic pressure for Internal Concentration Polarization reduction
Chemical Engineering Journal, 2014Co-Authors: Zhengzhong Zhou, Tai-shung ChungAbstract:Abstract Thin-film composite (TFC) forward-osmosis (FO) membranes with enhanced Internal osmotic pressure (IOP) were used to reduce Internal Concentration Polarization in this study. These TFC membranes contained a selective polyamide layer deposited by interfacial polymerization on a support substrate cast from a polymer blend of polysulfone (PSf) and sulfonated poly(phenylene oxide) (SPPO). The immobilized counter ions (Na + ) in SPPO gave rise to an IOP which facilitated water transport in the AL–FS operating mode (i.e., the active layer is facing the feed solution, also referred to as the FO mode) but retarded water transport in the AL–DS operating mode (i.e., the active layer is facing the draw solution, also called as the pressure retarded osmosis (PRO) mode). An optimized TFC membrane could draw a water flux of 39 LMH (Lm −2 h −1 ) in the AL–FS mode, which is among the highest in the current literature; and 57 LMH in the AL–DS mode, which is comparable to other published works using deionized water as the feed and 2 M NaCl as the draw solution. The optimized SPPO/PSf TFC membrane also outperformed other published FO membranes in simulated seawater desalination. Extremely high water fluxes of 25 and 19 LMH could be obtained in the AL–DS and AL–FS modes respectively. The impressive high water flux in the AL–FS mode makes this membrane particularly suitable for FO operations where Internal Concentration Polarization (ICP) and membrane fouling are major concerns.
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high performance thin film composite forward osmosis hollow fiber membranes with macrovoid free and highly porous structure for sustainable water production
Environmental Science & Technology, 2012Co-Authors: Panu Sukitpaneeni, Tai-shung ChungAbstract:The development of high-performance and well-constructed thin-film composite (TFC) hollow fiber membranes for forward osmosis (FO) applications is presented in this study. The newly developed membranes consist of a functional selective polyamide layer formed by highly reproducible interfacial polymerization on a polyethersulfone (PES) hollow fiber support. Using dual-layer coextrusion technology to design and effectively control the phase inversion during membrane formation, the support was designed to possess desirable macrovoid-free and fully sponge-like morphology. Such morphology not only provides excellent membrane strength, but it has been proven to minimize Internal Concentration Polarization in a FO process, thus leading to the water flux enhancement. The fabricated membranes exhibited relatively high water fluxes of 32–34 LMH and up to 57–65 LMH against a pure water feed using 2 M NaCl as the draw solution tested under the FO and pressure retarded osmosis (PRO) modes, respectively, while consiste...
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Corrigendum to "The role of sulphonated polymer and macrovoid-free structure in the support layer for thin-film composite (TFC) forward osmosis (FO) membranes" (J. Membr. Sci. 383 (2011) 214-223)
Journal of Membrane Science, 2012Co-Authors: Natalia Widjojo, Tai-shung Chung, Martin Weber, Christian Maletzko, Volker WarzelhanAbstract:The authors regret that typo errors appeared in the Refs. [12,36,37]. The correct spelling of first author name in these three references hould be J.R. McCutcheon as shown below: [12] J.R. McCutcheon, R.L. McGinnis, M. Elimelech, A novel ammonia–carbon dioxide forward (direct) osmosis desalination process, esalination 174 (2005) 1. [36] J.R. McCutcheon, M. Elimelech, Modeling water flow in forward osmosis: implications for improved membrane design, AIChE J. 53 2007) 1736. [37] J.R. McCutcheon, M. Elimelech, Influence of concentrative and dilutive Internal Concentration Polarization on flux behavior in orward osmosis, J. Membr. Sci. 284 (2006) 237. The authors apologize for this error.
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double skinned forward osmosis membranes for reducing Internal Concentration Polarization within the porous sublayer
Industrial & Engineering Chemistry Research, 2010Co-Authors: Kai Yu Wang, Tai-shung ChungAbstract:A scheme to fabricate forward osmosis membranes comprising a highly porous sublayer sandwiched between two selective skin layers via phase inversion was proposed. One severe deficiency of existing composite and asymmetric membranes used in forward osmosis is the presence of unfavorable Internal Concentration Polarization within the porous support layer that hinders both (i) separation (salt flux) and (ii) the performance (water flux). The double skin layers of the tailored membrane may mitigate the Internal Concentration Polarization by preventing the salt and other solutes in the draw solution from penetrating into the membrane porous support. The prototype double-skinned cellulose acetate membrane displayed a water flux of 48.2 L·m−2·h−1 and lower reverse salt transport of 6.5 g·m−2·h−1 using 5.0 M MgCl2 as the draw solution in a forward osmosis process performed at 22 °C. This can be attributed to the effective salt rejection by the double skin layers and the low water transport resistance within the p...
Xuan Zhang - One of the best experts on this subject based on the ideXlab platform.
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Improved performance of thin-film composite membrane supported by aligned nanofibers substrate with slit-shape pores for forward osmosis
Journal of Membrane Science, 2020Co-Authors: Chao Han, Xuan Zhang, Chun Ding, Shu Xiong, Yan WangAbstract:Abstract Substrate construction is considered as the most effective approach to alleviate the Internal Concentration Polarization (ICP) effect, and therefore achieves the excellent performance of resultant thin-film composite (TFC) membrane in forward osmosis (FO) process. In this work, a well-aligned nanofiber substrate was prepared and employed for constructing the high-performance TFC-FO membrane for the first time. The physicochemical properties of the substrate, the micro-structure of polyamide layer and the separation performance of resultant TFC-FO membranes were systematically investigated. Taking advantages of the larger pore size and the better pore interconnectivity of the well-aligned nanofiber substrate, the resultant TFC-FO membrane achieves the best water fluxes of 50.7 and 62.9 LMH, accompanied with the ultralow reverse salt flux in FO and PRO modes, using deionized water feed solution and 1 M NaCl aqueous draw solution. This work may provide a new orientation in developing high-performance TFC membranes.
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Sub-1 μm Free-Standing Symmetric Membrane for Osmotic Separations
Environmental Science & Technology Letters, 2019Co-Authors: Wei Cheng, Xuan Zhang, Menachem ElimelechAbstract:Desalination membranes have an asymmetric structure and thus experience severe Internal Concentration Polarization (ICP) in osmotic separations, such as desalination and water purification. ICP sub...
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Concentration and Recovery of Dyes from Textile Wastewater Using a Self-Standing, Support-Free Forward Osmosis Membrane
Environmental Science & Technology, 2019Co-Authors: Xi Wang, Xuan Zhang, Lianjun Wang, Wei Cheng, Cassandra J. Porter, Menachem ElimelechAbstract:Forward osmosis (FO) can potentially treat textile wastewaters with less fouling than pressure-driven membrane processes such as reverse osmosis and nanofiltration. However, conventional FO membranes with asymmetric architecture experience severe flux decline caused by Internal Concentration Polarization and fouling as dye molecules accumulate on the membrane surface. In this study, we present a new strategy for concentrating dye by using a self-standing, support-free FO membrane with a symmetric structure. The membrane was fabricated by a facile solution-casting approach based on a poly(triazole-co-oxadiazole-co-hydrazine) (PTAODH) skeleton. Due to its dense architecture, ultrasmooth surface, and high negative surface charge, the PTAODH membrane exhibits excellent FO performance with minimal fouling, low reverse salt flux, and negligible dye passage to the draw solution side. Cleaning with a 40% alcohol solution, after achieving a Concentration factor of ∼10, resulted in high flux recovery ratio (98.7%) ...
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construction of sio2 mwnts incorporated pvdf substrate for reducing Internal Concentration Polarization in forward osmosis
Journal of Membrane Science, 2018Co-Authors: Xuan Zhang, Liang Shen, Chen-yu Guan, Chu-xuan Liu, Wan-zhong Lang, Yan WangAbstract:Abstract This work provides a facile and effective way of incorporating SiO2@MWNTs in polyvinylidene fluoride (PVDF) substrate to alleviate the Internal Concentration Polarization (ICP) impact of the resultant thin film composite forward osmosis (TFC-FO) membranes for the first time. The in-situ decoration of multi-walled carbon nanotubes (MWNTs) using tetraethyl orthosilicate (TEOS) as precursor was conducted, resulting in improved hydrophilicity and the excellent dispersion of synthesized SiO2@MWNTs in PVDF membrane substrates accordingly. Effects of the SiO2@MWNTs Concentration on the morphologies and properties of the modified substrates, and further impact on the polyamide (PA) layer structure are investigated via various characterizations. Besides, the intrinsic separation properties and forward osmosis performance of resultant TFC-FO membranes are also systemically studied. In comparison with the control TFC membrane, SiO2@MWNT-modified TFC membranes exhibit higher water fluxes with the enhanced membrane selectivity, as indicated by the decreased JS/JV values (from 1.10 to 0.19 g/L). This work therefore presents an alternative approach to prepare TFC-FO membranes with enhanced water flux as well as increased selectivity.
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A Self-Standing, Support-Free Membrane for Forward Osmosis with No Internal Concentration Polarization
Environmental Science & Technology Letters, 2018Co-Authors: Vasiliki Karanikola, Xuan Zhang, Lianjun Wang, Menachem ElimelechAbstract:Conventional asymmetric or thin-film composite forward osmosis (FO) membranes suffer from severe Internal Concentration Polarization, which significantly hinders process performance and practical applications. Here we report the synthesis of the COOH-derived polyoxadiazole copolymer for the fabrication of a self-standing selective thin film without a support layer. The thickness of the membrane was controlled at merely a few micrometers to achieve a high rate of rejection of the Na2SO4 draw solution, while maintaining acceptable water permeability. Because of the symmetric architecture, the membrane exhibited excellent and identical FO performance at both of its sides. The structural parameter of the fabricated membranes was zero because of the absence of Internal Concentration Polarization in the symmetric FO membranes. Our results highlight the potential of support-free membranes for the further development of FO technology.