High-performance Thin-film Composite Membranes Research Articles

Improving the water permeability and antifouling property of the nanofiltration membrane grafted with hyperbranched polyglycerol

This study evaluated the performance of the high performance nanofiltration (NF) membrane by grafting the recently developed hyperbranched polyglycerol (hPG) with a unique three-dimensional (3D) globular structure and superhydrophilicity on thin-film composite (TFC) polyamide layer. The hPG modified TFC (hPG-TFC) NF membrane possessed an outstanding hydrophilic surface and high permeance without compromising salt rejection. Compared with the pristine TFC membrane, the hPG modified membrane exhibited a permeate flux increase of 30% while maintaining Na2SO4 rejection of 97%. Irrespective of foulants, the hPG grafted TFC persistently generated an enhanced antifouling ability. Among the model foulants, the humid acid shows the most severe fouling potential for NF membranes. Notwithstanding, the hPG-TFC exhibits an improved normalized water flux of 65% and flux recovery of 75%, much higher than the pristine TFC membrane (44% and 47%, respectively). In addition, in order to better understand the antifouling behavior of our hPG modified NF membranes, the Q-sense quartz-crystal microbalance with dissipation (QCM-D) was used to determine both the adsorption rate and amount of model foulants on the membrane surface. Therefore, the successful application of 3D hPG polymers on the NF membrane should serve as a source of inspiration for the surface engineering of high performance TFC membrane with high water permeability and enhanced antifouling performance in pressure-driven NF membrane processes.

Improved performance of thin-film composite membrane supported by aligned nanofibers substrate with slit-shape pores for forward osmosis

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.

Effect of the support layer morphological structure on the performance of forward osmosis hollow fiber membranes

A thin-film polyamide layer was synthesized on three different hollow-fiber support layers, each of which possess different morphological structures (i.e., sponge-like structures (SM-1), finger-like macrovoid close to the outer surface (SM-2), and middle-partitioned finger-like structures (SM-3)). In this work, we found that forward osmosis (FO) performance of thin-film composite (TFC) membranes could be significantly affected by their sub-layer morphology. During FO tests, SM-1 showed the highest water permeability of 0.742 LMH/bar followed by SM-3 and SM-2. In addition, SM-1 exhibited the lowest solute permeability of 0.039 LMH, followed by SM-2 and SM-3. To more systematically evaluate the effect of the support layer structures on the performance of TFC FO membranes, the structural parameters (S) of the membranes were estimated using the dusty gas model (DGM) prior to interfacial polymerization on the support layers. The S values of the support layers obtained from the DGM method are in accord with the FO membrane performance. Although the conventional S parameter determination method showed relatively similar values with the DGM method, the overall trend corresponds, confirming that the smaller S value is related to a smaller internal concentration polarization decrease. Moreover, this study clearly demonstrates that the support layer needs to be considered alongside the active layer of TFC FO membranes, and that a sponge-like support layer can be a better option for high-performance FO TFC membranes.

Toward enhancing the separation and antifouling performance of thin-film composite nanofiltration membranes: A novel carbonate-based preoccupation strategy

High-performance nanofiltration (NF) membranes with simultaneously improved antifouling and separation performance are of great significance for environmental water purification. In this work, a high-performance thin-film composite (TFC) NF membrane (TFC-Ca) was constructed through in-situ incorporation of calcium bicarbonate during interfacial reaction. The surface morphology and chemical structure of the TFC-Ca membrane were systematically investigated by FTIR, XPS, AFM, and SEM. The results indicated that the surface characteristics of the pristine NF membrane were greatly changed by the incorporation of calcium bicarbonate. The TFC-Ca membrane exhibited improved hydrophilicity, narrowed pore size, declined negative charge, and increased surface area. Compared to the control membrane, the TFC-Ca membrane possessed a much greater water permeability and higher molecule rejections. For the TFC-Ca membrane, an optimized water permeance of 13.4 ± 0.3 L m−2 h−1 bar−1 with 99.9% Na2SO4 rejection was obtained. Impressively, the TFC-Ca membrane exhibited excellent antifouling performance during 5 cycles of humic acid fouling tests. A satisfactory flux recovery up to 90.0% was achieved after physical cleaning for the optimized membrane. Furthermore, the TFC-Ca membrane also presented superior performance stability when treated with strong acid and chelating agents for 7 days. Overall, this facile preoccupation strategy via in-situ incorporation of calcium bicarbonate allows the fabrication of high-performance TFC membranes with outstanding separation and antifouling properties.

Constructing substrate of low structural parameter by salt induction for high-performance TFC-FO membranes

Forward osmosis (FO) is a promising membrane-based technology for water treatment and desalination. But, internal concentration polarization (ICP), a unique phenomenon in FO, generally leads to the sharp performance decline. In this study, a novel polyacrylonitrile (PAN) substrate with low polymer concentration (4 wt%) of the thin-film composite (TFC) membrane with a low membrane structural parameter (S) is developed with sodium chloride (NaCl) aqueous solution as the coagulation bath, and exhibits high performance for FO applications. The existence of NaCl in the coagulation bath not only affects the phase inversion process significantly, resulting in the formation of a thin substrate with finely tuned morphology structure, but also benefits the formation of a uniform and defect-free top polyamide (PA) layer. Effects of NaCl content in the coagulation bath on the morphology and intrinsic properties of resulting PAN substrates, the formed PA layer, as well as the morphology and FO performance of resulting TFC membranes, are investigated systematically. Moreover, an extended study on cellulose acetate (CA) substrate is also conducted to study the universality of this salt induction method to fabricate high-performance TFC membranes. Compared to the control TFC membrane, modified TFC membranes show much lower S parameters and superior separation performance with the higher water flux (324% increment) and lower reverse salt flux (58% reduction).

Effect of ultrasonication parameters on forward osmosis performance of thin film composite polyamide membranes prepared with ultrasound-assisted interfacial polymerization

High-performance thin-film composite (TFC) membranes with a high water permeability and high salt rejection are requisites for the successful development of the forward osmosis technology. Based on our previous work on high-performance TFC membranes obtained by a novel ultrasound-assisted interfacial polymerization with different ultrasonication powers, this work conducts a comprehensive investigation of the effects of various ultrasonication parameters including ultrasonication power, frequency, and time on the membrane performance. The effects of the ultrasonication parameters on the chemical and surface properties, morphology, free volume, and the corresponding separation performance characteristics were investigated systematically. The modified TFC membrane obtained at the optimized ultrasonication conditions shows a water flux of 120.1 ± 2.1 LMH (2.6 times higher than that of the control membrane) and a reverse salt flux of 12.1 ± 0.7 gMH (34.2% reduction relative to that of the control membrane) in the pressure retarded osmosis mode with the draw solution of 2 M NaCl and the feed solution of deionized water.

A Facile and Scalable Fabrication Procedure for Thin-Film Composite Membranes: Integration of Phase Inversion and Interfacial Polymerization.

Conventional dense thin-film composite (TFC) membranes evince a universally low water permeability, the increase of which typically relies on introducing additional transport channels based on intricate steps within a membrane preparation process. In this study, we reported a novel and simplified procedure for the fabrication of high-performance TFC membranes. Specifically, the dissolution of aqueous monomers in the casting solution was utilized for the following interfacial polymerization (IP). Since the monomers diffused to the water bath during phase inversion, the control of precipitation time enabled an effective regulation of the monomer concentration in the formed polymeric substrates, where the IP reaction was initiated by the addition of the organic phase. The entire and uniform embedment of aqueous monomers inside the substrates contributed to the formation of ultrathin and smooth selective layers. An excellent separation performance (i.e., water permeability: 34.7 L m-2 h-1 bar-1; Na2SO4 rejection: ∼96%) could be attained using two types of aqueous monomers (i.e., piperazine and β-cyclodextrin), demonstrating the effectiveness and universality of this method. Compared to the conventional immersion-based process, this novel procedure shows distinct advantages in reducing monomer usage, shortening the production cycle, and achieving a more superior membrane performance, which is highly promising for large-scale membrane manufacture.

Fabrication of high performance nanofiltration membrane on a coordination-driven assembled interlayer for water purification

A facile coordination-driven assembly strategy is proposed to construct a multifunctional PSS-metal ions complex interlayer on the substrate for the fabrication of the high performance thin-film composite (TFC) NF membrane with crumpled morphology. The PSS-metal ions interlayer not only acts as nanoscaffold role to provide a more uniform interfacial polymerization (IP) platform that is favorable for forming a thinner and free-defect PA layer with less PA intruded into the pores of support, but also works as macromolecule addition to induce the diffusion-driven instability of IP process that causes the creation of the crumpled PA layer with increased surface area, of which dual roles in regulating the IP process are confirmed by the comprehensive characterization of the top and back surface morphologies and structure of the selective layer. As such, the obtained TFC membrane exhibits a four folds of permeance (up to 22.15 ± 1.14 L m−2 h−1 bar−1) as compared with traditional TFC-0 membrane, while maintaining a competitive rejection for Na2SO4 (about 99.3%). Moreover, owing to the increased surface negative charges and decreased effective pore size, the novel NF membrane shows a simultaneous high rejection of trace organic compounds (TrOCs) and low retention of divalent cation (Ca2+/Mg2+) in a real tap water, suggesting that it has great potential in drinking water treatment. This study provides a new direction to prepare the high-performance TFC membrane for water purification.

Postcombustion Carbon Capture Using Thin-Film Composite Membranes.

Climate change due to anthropogenic carbon dioxide emissions (e.g., combustion of fossil fuels) represents one of the most profound environmental disasters of this century. Equipping power plants with carbon capture and storage (CCS) technology has the potential to reduce current worldwide CO2 emissions. However, existing CCS schemes (i.e., amine scrubbing) are highly energy-intensive. The urgent abatement of CO2 emissions relies on the development of new, efficient technologies to capture CO2 from existing power plants. Membrane-based CO2 separation is an attractive technology that meets many of the requirements for energy-efficient industrial carbon capture. Within this domain, thin-film composite (TFC) membranes are particularly attractive, providing high gas permeance in comparison with conventional thicker (∼50 μm) dense membranes. TFC membranes are usually composed of three layers: (1) a bottom porous support layer; (2) a highly permeable intermediate gutter layer; and (3) a thin (<1 μm) species-selective top layer. A key challenge in the development of TFC membranes has been to simultaneously maximize the transmembrane gas permeance of the assembled membrane (by minimizing the gas resistance of each layer) while maintaining high gas-specific selectivity. In this Account, we provide an overview of our recent development of high-performance TFC membrane materials as well as insights into the unique fabrication strategies employed for the selective layer and gutter layer. Optimization of each layer of the membrane assembly individually results in significant improvements in overall membrane performance. First, incorporating nanosized fillers into the selective layer (poly(ethylene glycol)-based polymers) and reducing its thickness (to ca. 50 nm) through continuous assembly of polymers technology yieldsmajor improvements in CO2 permeance without loss of selectivity. Second, we focus on optimization of the middle gutter layer of TFC membranes. The development of enhanced gutter layers employing two- and three-dimensional metal-organic framework materials leads to considerable improvements in both CO2 permeance and selectivity compared with traditional poly(dimethylsiloxane) materials. Third, incorporation of a porous, flexible support layer culminates in a mechanically robust high-performance TFC membrane design that exhibits unprecedented CO2 separation performance and holds significant potential for industrial CO2 capture. Alternative strategies are also emerging, whereby the selective layer and gutter layer may be combined for enhanced membrane efficiency. This Account highlights the CO2 capture performance, current challenges, and future research directions in designing high-performance TFC membranes.

Calcium-Carboxyl Intrabridging during Interfacial Polymerization: A Novel Strategy to Improve Antifouling Performance of Thin Film Composite Membranes.

This study reports a novel intrabridging strategy to improve the antifouling performance of a thin-film composite (TFC) membrane. We demonstrate that the addition of Ca2+ during the interfacial polymerization reaction led to the formation of stable Ca2+-carboxyl complexes within the polyamide rejection layer. This intrabridging of carboxyl groups by Ca2+ effectively sequestrated them, reducing their availability for binding divalent metal ions in the aqueous solution and for forming foulant-metal-membrane interbridges. Membrane fouling and cleaning experiments confirmed improved flux stability and fouling reversibility for the Ca2+ modified membranes. The greatly enhanced antifouling performance of these membranes, together with their better surface hydrophilicity and greater water permeability, makes the intrabridging approach highly attractive in overcoming the classical permeability-selectivity-antifouling trade-off. Our findings pave a new direction for synthesizing high-performance TFC membranes.

Tannic Acid/Fe3+ Nanoscaffold for Interfacial Polymerization: Toward Enhanced Nanofiltration Performance.

Conventional thin-film composite (TFC) membranes suffer from the trade-off relationship between permeability and selectivity, known as the "upper bound". In this work, we report a high performance thin-film composite membrane prepared on a tannic acid (TA)-Fe nanoscaffold (TFCn) to overcome such upper bound. Specifically, a TA-Fe nanoscaffold was first coated onto a polysulfone substrate, followed by performing an interfacial polymerization reaction between trimesoyl chloride (TMC) and piperazine (PIP). The TA-Fe nanoscaffold enhanced the uptake of amine monomers and provided a platform for their controlled release. The smaller surface pore size of the TA-Fe coated substrate further eliminated the intrusion of polyamide into the substrate pores. The resulting membrane TFCn showed a water permeability of 19.6 ± 0.5 L m2- h-1 bar-1, which was an order of magnitude higher than that of control TFC membrane (2.2 ± 0.3 L m-2 h-1 bar-1). The formation of a more order polyamide rejection layer also significantly enhanced salt rejection (e.g., NaCl, MgCl2, Na2SO4, and MgSO4) and divalent to monovalent ion selectivity (e.g., NaCl/MgSO4). Compared to conventional TFC nanofiltration membranes, the novel TFCn membrane successfully overcame the longstanding permeability and selectivity trade-off. The current work paves a new avenue for fabricating high performance TFC membranes.

High-performance thin-film composite membranes with surface functionalization by organic phosphonic acids

Forward osmosis (FO), a novel promising technology for water treatment, has not progressed significantly beyond the conceptualization. A bottleneck is the lack of suitable membranes with high separation performance, good antifouling properties and chemical stability. In this work, a 3-step surface modification approach is employed to develop a thin-film composite polyamide (TFC PA) membrane, i.e., PEI grafting, acid functionalization (organic phosphonic acid or carboxylic acid), and the calcium mineralization. Effects of the organic acid type on membrane properties are investigated with various characterizations, in terms of chemical changes, surface properties, and morphology. The separation performance, antifouling properties and chemical stability of modified membranes are studied systematically. In comparison with the control membrane and those modified by organic carboxylic acids, membranes modified by organic phosphonic acids exhibit the higher FO water flux, lower reverse salt flux, lower fouling propensity, a better pH tolerance, as well as a superior chlorine resistance. The surface functionalized TFC membrane developed in this work therefore holds a great potential for wide membrane-based separation applications in various harsh environments.

High-Performance Thin-Film Composite Membrane with an Ultrathin Spray-Coated Carbon Nanotube Interlayer

We fabricated a thin-film composite (TFC) forward osmosis (FO) membrane with an ultrathin spray-coated carbon nanotube (CNT) interlayer. The impact of the CNT interlayer on the polyamide (PA) layer structural properties and transport behavior in FO were investigated. Results indicate that the CNT interlayer provides an interface which enables the formation of a highly permeable and selective PA layer with a large effective surface area for water transport, while inhibiting the formation of a flower-like PA structure inside the substrate pores. The TFC-FO membrane with the CNT interlayer exhibited a much greater water flux than previously reported for FO membranes, while maintaining comparable salt rejection. Specifically, a membrane perm-selectivity or ratio of water (A) to salt permeability coefficients (B) (A/B value) of 39 bar–1 was achieved for the TFC-PA-CNT membrane. Implications of the results for the fabrication of high-performance TFC-FO membranes are further discussed.

High-flux thin film composite membranes for nanofiltration mediated by a rapid co-deposition of polydopamine/piperazine

A novel thin film composite (TFC) membrane was rationally originated using an interfacial polymerization (IP) process mediated by a rapid Cu2+/H2O2-induced co-deposition of PDA and piperazine (PIP). The co-deposition strategy distinctly shortens modification times while also promoting the high, stable loading of aqueous monomers through covalent bonding with PDA, thus being beneficial for subsequent crosslinking with trimesoyl chloride (TMC). The controlled diffusion of aqueous monomers during the IP process enabled the formation of a thin, smooth, and hydrophilic polyamide (PA) film at the top of a polyacrylonitrile (PAN) membrane substrate. ATR-FTIR, XPS, SEM, AFM, and water contact angle analyses confirmed the presence of the selective PA layer. Zeta potential measurements also revealed a negatively charged surface, which resulted in a salt retention order of NaCl < MgCl2 < MgSO4 < Na2SO4. The roles of the co-deposition time and the PIP/dopamine ratio in the membrane morphology and separation properties were systematically studied to explore the optimal functionalization parameters. A high-performance TFC membrane (TFC2.0_5) was achieved after identifying optimal conditions as 2/1 mass ratio for PIP/dopamine, 5 min co-deposition, 0.1% w/v TMC, and 30 s IP reaction. In addition to achieving high water permeability (14.5 LMH bar−1), this membrane also attained high mono/bivalent salt selectivity (NaCl/Na2SO4, 24.1) and long-term stability in treating saline solutions. This simple, and cost-effective strategy provides an improved guideline in designing high-performance TFC membranes with vast potential in water treatment.

Thin film composite membranes containing intrinsic CD cavities in the selective layer

In this work, β-cyclodextrin functionalized with multiple ethylenediamine groups (β-CD-EDA) is synthesized and employed as a novel amine monomer for the preparation of thin film composite (TFC) membrane via the interfacial polymerization (IP) with trimesoyl chloride (TMC), to incorporate uniformly-distributed intrinsic CD cavities into the polymer network of the selective layer. The chemical structure of the synthesized β-CD-EDA is confirmed by HMRS, FTIR, TGA XPS and 1H NMR. The chemical properties, surface morphology and the separation performance of TFC membranes prepared with β-CD (TFC_β-CD) and β-CD-EDA (TFC_β-CD-EDA) as aqueous monomers are investigated and compared. The effects of the IP time and β-CD-EDA concentration on the membrane properties are investigated to optimize the membrane performance. The separation performances of TFC_β-CD-EDA membrane are further evaluated with feed solutions containing different solutes. It is found that TFC_β-CD-EDA membranes demonstrated competitive water permeabilities and high rejections to common divalent anionic salts and small organics, contributed by the CD cavities that enable the fast transport of water molecules but restrict larger ions or molecules. Besides, excellent fouling resistance of TFC_β-CD-EDA membrane is also found, because of the embedded CD rings with plentiful hydroxyls. This work is therefore believed to provide a facile method for the development of high-performance TFC membrane with pore-containing selective layer.

Surface Engineering of Thin Film Composite Polyamide Membranes with Silver Nanoparticles through Layer-by-Layer Interfacial Polymerization for Antibacterial Properties.

We developed a simple and facile approach to covalently immobilize Ag nanoparticles (NPs) onto polyamide surfaces of thin film composite membranes through layer-by-layer interfacial polymerization (LBL-IP) for biofouling mitigation. Stable and uniform bovine serum albumin (BSA) capped Ag NPs with an average diameter of around 20 nm were synthesized using BSA as a template under the assistance of sonication, and Ag NPs incorporated thin film composite (TFC) polyamide membrane was then fabricated by LBL-IP on a nanoporous polysulfone (PSf) substrate upon sequential coating with m-phenylenediamine (MPD) aqueous solution, trimesoyl chloride (TMC)-hexane solution, and finally BSA-capped Ag NPs aqueous solution. The influence of Ag NPs incorporation was investigated on the surface physicochemical properties, water permeability, and salt rejection of TFC polyamide membrane. Our findings show that Ag NPs functionalized membrane exhibited excellent antibacterial properties without sacrificing their permeability and rejection, and Ag NPs incorporation affected very little surface roughness and charge of polyamide layer. Moreover, the incorporated Ag NPs presented a low release rate and excellent stability on polyamide surface in cross-flow conditions. Given the simplicity and versatility of this approach, our study provides a practicable avenue for direct incorporation of various surface-tailored nanomaterials on the polyamide surface to develop high-performance TFC membranes with fouling-resistant properties on a large scale.

Synthesis of thin film composite polyamide membranes: Effect of monohydric and polyhydric alcohol additives in aqueous solution

Thin film composite (TFC) polyamide (PA) membranes are the most widely used membranes in current water filtration processes. Over the past decade, extensive efforts have been made to improve the permeation properties of the TFC PA membranes via different techniques. In the present work, the effect of incorporating monohydric and polyhydric alcohols into the aqueous solution on surface morphology and permeation properties of resulting TFC PA membranes was studied. The TFC PA membranes were prepared by interfacial polymerization (IP) reaction between m-phenylenediamine (MPD)-aqueous and trimesoyl chloride (TMC)-hexane solutions over polyethersulfone (PES) support. Different concentrations of ethanol (C2H6O), ethylene glycol (C2H6O2), and xylitol (C5H12O5) were added into the MPD-aqueous solution. The results showed that addition of alcohols with low molar volumes such as ethanol and ethylene glycol significantly improved water flux of the synthesized membranes. However, in the case of alcohols with larger molar volumes, like polyhydric xylitol, the water flux enhanced by increasing the alcohol concentration up to ~1.0wt%, and then decreased, suggesting the presence of an optimum concentration of xylitol. This observation indicated the presence of a complex interaction between the hydrophilic hydroxyl groups and hydrophobic aliphatic carbon chain in the structure of large alcohol molecules. Furthermore, all the modified membranes showed higher rejection percentage than the original membrane which is highly desirable for fabrication of high-performance TFC membranes. The findings of this study provide insight into the synergistic effects of structural properties and surface characteristics, which are altered by the addition of alcohols, on the permeation properties of the TFC membranes.

Developing high throughput thin film composite polyamide membranes for forward osmosis treatment of SAGD produced water

Application of thin film composite (TFC) membranes for forward osmosis (FO) separation processes has attracted growing attention due to their outstanding permeation properties as compared to conventional asymmetric membranes. The aim of the present study is to fabricate high-performance TFC membranes by an innovative adjustment of interfacial polymerization (IP) reaction between m-phenylenediamine (MPD) and trimesoyl chloride (TMC) at the surface of a polyethersulfone (PES) microporous support. It was found that reducing the temperature of the organic solution down to −20°C effectively reduced the thickness of the PA selective layer and thus, significantly enhanced water permeation through the membranes. The water flux increased more than double from 17.6LMH for membranes prepared at 25°C to 38.5LMH at −20°C, when 3M NaCl solution and de-ionized water were used as draw and feed solutions, respectively. In addition, all the lab-made membranes showed significantly lower specific solute flux than the commercial membrane. The performance of lab-synthesized TFC membranes was also evaluated for the treatment of boiler feed water (BFW) of steam assisted gravity drainage (SAGD) process. The results showed superior permeation properties of lab-made membranes to commercially available TFC-FO membranes. This was attributed to the thinner PA selective layer and lower structural parameter (451±13) of the lab-made membranes compared to the commercial membrane (1770μm) which alleviated the effect of internal concentration polarization (ICP) remarkably. This study provides valuable guidelines for an effective tuning of the organic solution temperature during the IP reaction to develop high-throughput TFC FO membranes.

High performance thin-film composite membranes with mesh-reinforced hydrophilic sulfonated polyphenylenesulfone (sPPSU) substrates for osmotically driven processes

We have for the first time combined the strength of hydrophilic sulfonated material and thin woven open-mesh via a continuous casting process to fabricate mesh-reinforced ultrafiltration (UF) membrane substrates with desirable structure and morphology for the development of high-performance thin-film composite (TFC) osmosis membranes. A new sulfonated polyphenylenesulfone (sPPSU) polymer with super-hydrophilic nature is used as the substrate material, while a hydrophilic polyester (PET) open-mesh with a small thickness of 45μm and an open area of 44.5% is employed as the reinforcing fabric during membrane casting. The newly developed sPPSU-TFC membranes not only exhibit a fully sponge-like cross-section morphology, but also possess excellent water permeability (A=3.4–3.7Lm−2h−1bar−1) and selectivity toward NaCl (B=0.10–0.23Lm−2h−1). Due to the hydrophilic nature and low membrane thickness of 53–67μm, the PET-woven reinforced sPPSU substrates have remarkably small structural parameters (S) of less than 300μm. The sPPSU-TFC membranes thereby display impressive water fluxes (Jw) of 69.3–76.5Lm−2h−1 and 38.7–47.0Lm−2h−1 against a deionized water feed using 2M NaCl as the draw solution under pressure retarded osmosis (PRO) and forward osmosis (FO) modes, respectively. This performance surpasses the state-of-the-art commercially available FO membranes. The sPPSU-TFC membranes also show exciting performance for synthetic seawater (3.5wt% NaCl) desalination and water reclamation from real municipal wastewater. The newly developed PET-woven sPPSU-TFC membranes may have great potential to become a new generation membrane for osmotically driven processes.

Membrane-Based Oxygen-Enriched Combustion

The use of oxygen-enriched air, instead of ambient air, can significantly improve the energy efficiency of combustion processes and reduce the cost of CO2 capture from flue gases throughout manufacturing industries. This study examines the overall energy savings and economic benefits that can be obtained using oxygen-enriched combustion based on novel membranes and processes to produce oxygen-enriched air. Membrane processes using low-pressure air as a countercurrent sweep in the permeate were used to minimize the energy cost of producing oxygen-enriched air. High-performance thin film composite membranes based on a series of perfluoropolymers and bench-scale spiral-wound modules were prepared, and showed oxygen permeance as high as 1200 gpu (1 gpu = 10–6 cm3(STP)/cm2·s·cmHg) combined with O2/N2 selectivity of 3.0. The membrane-based oxygen-enriched combustion processes show good energy savings (defined as the fuel savings less the energy consumption of producing oxygen-enriched air) and economic benefits...