A zeolite composite membrane (ZCM) was designed and fabricated via a simple versatile and scalable method. A thin layer of ZSM-35 flakes with pore size between hydrated protons and vanadium ions was fixed on the poly (ether-sulfone)/sulfonated poly(ether-ether-ketone) (PES/SPEEK) porous substrate by in-situ interfacial polymerization. The ZSM flake layer can perfectly separate hydrated vanadium ions and protons, therefore, show very impressive performance for vanadium flow batteries (VFBs). As a result, a VFB assembled with an optimized ZCM exhibited a columbic efficiency more than 99% and energy efficiency of over 91% at a current density of 80 mA cm(-2), which is among the highest performance ever reported. Furthermore, the energy efficiency can reach 81.6% at a very high current density of 200 mA cm(-2) and keep stable for 1000 cycles at a current density of 180 mA cm(-2). This method opened a door toward the large-scale production of highly selective composite membranes for flow batteries.
In this paper, a series of sulfonated poly(ether ether ketone) (SPEEK) hybrid membranes containing aliphatic amine-functionalized graphene oxide nanofillers as the interface modifiers, reacted with primary amine (NH2-GO), ethylenediamine (EDA-GO) and 1,6-hexanediamine (HMD-GO), respectively, have been fabricated via a simple solution-casting method. Three hybrid membranes (S/NH2-GO, S/EDA-GO, and S/HMD-GO) demonstrate much higher physicochemical property than that of pristine SPEEK and Nafion 117, which is originated from the varied interfacial interaction and the surface architecture behavior. A superior ion selectivity of S/EDA-GO-1 (24.8 10(3) S min cm(-3)), S/HMD-GO-2 (24.6 x 10(3) S min cm(-3)) and S/NH2-GO-2 (20.4 x 10(3) S min cm(-3)) to pristine SPEEK (4.3 x 10(3) S min cm(-3)) and Nafion 117 membrane (4.0 x 10(3) S min cm(-3)) is shown. At the current density of 50 mA cm(-2), S/EDA-GO-1 hybrid membrane gives the highest energy efficiency than that of S/NH2-GO-2 and S/HMD-GO-2, endowing an excellent charge capacity retention during 100 cycles. The varied interfacial structure state originated from the introduced EDA-GO and HMD-GO nanofillers provide the different proton conductivity and vanadium ion permeability. This present work provides a guidance for developing high-performance PEMs through the regulated interfacial structure via the moderate chain length.
Silicon carbide (SiC) filters and porous membranes is a growing industry with deployment for gas and liquid separation processes. In view of its importance, the research efforts into the development of SiC filters and membranes are of growing interest around the world. Therefore, this review paper is focused on the latest ad-vancements in SiC and SiC composites used for the preparation of substrates and thin films in filters and membranes. There is a multitude of methods used to prepare filters and membranes of different shapes (tubular, honeycomb, flat sheets and multi-channel), which are influenced by precursor mixture and sintering conditions. In turn, these processing conditions affect porosity and pore size, which affects the transport and separation properties of SiC filters and membranes. SiC particles size and distribution allow for the precise control of pore size in membranes, leading to high gas separation factors. In addition, SiC has strong thermal stability properties that are very desirable for high temperature gas cleaning. Together with gas and liquid transport and separation properties, this review also addresses the potential applications in gas and liquid separation processes, coupled with thermal/chemical stability properties. Future challenges are highlighted towards further research efforts.
Lim, Yu Jie;Lee, Jaewoo;Bae, Tae-Hyun;Torres, Jaume;Wang, Rong
来源期刊：Journal of Membrane Science
Although a highly porous support membrane has attracted increasing attention as an alternative to enhance the water permeability of a thin-film composite (TFC) membrane without compromising salt rejection, its feasibility has not ever been tested in seawater desalination. This study explored the availability and potential of a highly porous microstructured (HP mu S) support membrane as a support for a seawater reverse osmosis (SWRO) membrane. Our lab-made membranes, TFC-HP mu S, exhibited a higher water permeability of 1.62 L m(-2) h(-1) bar(-1) as compared with most of the state-of-the-art SWRO membranes recently reported in the literature, while achieving comparable NaCl rejection (99%) in SWRO test condition (55 bar, 35,000 mg L-1 of NaCl). This excellent performance is thought to stem from the HP mu S support endowing a TFC membrane with comparable mechanical properties to that of existing support used for conventional SWRO membrane and shortened effective diffusion pathway of water molecules over the active layer. The robustness and enhanced mechanical strength of the TFC-HP mu S membrane are attributed to its narrow and regularly arranged finger-like structure ensuring the even distribution of local stresses, thereby eliminating the presence of stress convergence points. The shortened effective diffusion pathway was estimated to be achieved mainly by less localized surface pores due to the HP mu S support's highly porous surface with a larger number of even distributed surface pores. This study potentially opens up another workable pathway in the fabrication of SWRO membranes with enhanced performance without significant sacrifice of the selectivity.
Covalent grafting of polystyrene sulfonic acid (PSSA) on graphene oxide nanoplatelets (GONP) via in situ radical polymerization was conducted. PSSA-g-GONP is used as an additive to form a nanocomposite membrane with sulfonated poly(ether ether ketone) (sPEEK) for its application in direct methanol fuel cells (DMFCs), with better physicochemical properties and reduced methanol crossover compared to that of pristine sPEEK. The optimized sPEEK/PSSA-g-GONP (0.15 wt %) nanocomposite membrane exhibits a DMFC peak power density of 170 mW cm(-2), which is 50 % greater than the 110 mW cm(-2) for pristine sPEEK and one-fold greater than that of 80 mW cm(-2) observed for commercial Nafion (R) 117 due to its high electrochemical selectivity. Furthermore, the nanocomposite membrane shows better durability up to 100 h compared with sPEEK and Nafion (R) 117 electrolyte membranes, demonstrating its potential in diverse membrane applications.
Mixed matrix membranes (MMMs) have shown great advantages in overcoming the Robeson trade-off effect, and various fillers have been utilized to improve the gas permeation and separation performance. In this study, hollow polypyrrole (PPy) nanospheres with mesoporous shells were synthesized by chemical polymerization using hard template method. The hollow PPy nanospheres with mesoporous shells were investigated by transmission electron microscopy, scanning electron microscopy, Brunauer Emmett Teller and small-angle X-ray scattering. We introduced hollow PPy nanospheres into poly(ether-block-amide) (Pebax1657) as fillers to prepare MMMs for CO2 separation. The effects of the hollow PPy nanospheres on the physical properties and the gas permeation and separation performance were studied. The results showed that the addition of hollow PPy nanospheres contributed to the improvement of the gas permeability. At 1 wt% loading of hollow PPy nanospheres, the MMMs exhibited a highest CO2 permeability of 274 Barrer, which was more than double compared with that of the pure Pebax membrane, accompanied by the slightly increased CO2/N-2 selectivity of 40.1 and the slightly increased CO2/CH4 selectivity of 12.8. MMMs with hollow polymer nanospheres display a positive potential application for industrial-scale CO2 separation.
Antifouling poly(ether sulfone) (PES) composite membranes with novel bi-continuous porous structures, high fluxes and hydrophilic surfaces are successfully prepared by simultaneously manipulating the migration of amphiphilic three-block polymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic (R) F127) to the membrane surfaces and the microstructures of membranes by vapor-induced phase separation (VIPS) method. Effects of the additive mass ratios of Pluronic (R) F127 to PES and VIPS process parameters, including the dissolution and vapor temperature (T), the relative humidity of vapor (RH) and the exposure time to vapor (t), on microstructures of membranes and the surface hydrophilicity of membranes are systematically investigated. When the additive mass ratio of Pluronic (R) F127 to PES is 100%, PES/Pluronic (R) F127 composite membranes with bi-continuous porous structure across the full cross-section can be easily fabricated. For the composite membranes with additive mass ratio of 100%, when t = 1 min, the water contact angles of membranes decrease remarkably when the temperature increases from T = 25 degrees C to T = 40 degrees C. For the PES/Pluronic (R) F127 composite membranes prepared via VIPS method with T = 25 degrees C, RH = 70% and t = 20 min, the water contact angle is as low as 34.5 degrees, the water flux is as high as 236512 L m(-2) h(-1) bar(-1) and the static adsorption amount of bovine serum albumin (BSA) is only 4.6 mu g cm(-2). Valuable guidance is presented in this study about the design and fabrication of antifouling membranes with high flux and hydrophilic surfaces.
To meet highly conductive and chemical stable anion exchange membranes (AEMs), a series of multi-block poly (ether sulfone)s with long side chains densely terminated by piperidinium (bPES-Pip-X-Y) are synthesized. The multi-block structure and the aggregation of ionic groups on the flexible side chains are responsible for the distinct hydrophilic/hydrophobic microphase separation, which can be observed via transmission electron microscopy (TEM). The resulted membranes achieve the high conductivity (in-plane) of 48.5-105.4 mS cm(-1) at 80 degrees C. Moreover, the AEMs prepared exhibit good alkaline stability due to the presence of cation-terminated long side chain structure. The bPES-Pip-10-5 membrane still maintains 88% of the original conductivity after treated in 1 M KOH solution at 60 degrees C for 336 h. The membrane electrode assembly based on bPES-Pip-10-5 with a power density of 136.9 mW cm(-2) at a current density of 292.5 mA cm(-2) is obtained.
Membrane-based separation of organic/organic mixtures is of great importance in the chemical and petro-chemical industries, but remains very challenging owing to the harsh working conditions. Herein, ultrathin and chemically stable Bis(triethoxysilyl)acetylene (BTESA)-derived organosilica membranes were reproducibly pre-pared, and for the first time they were utilized in the pervaporation separation of methanol/organic azeotropes. The as-prepared BTESA membranes exhibited exceptional pervaporation performance in a 10 wt%/90 wt% methanol/dimethyl carbonate (DMC) mixture, and showed a high separation factor of approximately 120 with a permeation flux of 2-4 kg m(-2) h(-1) at 50 degrees C. This impressive performance was primarily the result of the pref-erential sorption of methanol and the efficient size sieving of DMC. In addition, the effects of feed concentration and temperature on methanol/DMC pervaporation performance were thoroughly investigated. Importantly, a generalized solution-diffusion model successfully described the pervaporation performance of BTESA mem-branes, and the usefulness of this model was further confirmed via the pervaporation of methanol/methyl acetate and methanol/methyl tert-butyl ether (MTBE) mixtures. This work demonstrates the great potential of orga-nosilica membranes for high-performance organic/organic pervaporation.
We explore the feasibility of utilizing electro-responsive hydrogels as novel forward osmosis (FO) draw agents for desalination. The chemically cross-linked hydrogels were synthesized via free radical copolymerization of common acrylamide (AM) with strong anionic comonomer 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). The morphology, chemical structure, water-adsorbing capacity, and water state of the hydrogels were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), a swelling test, and differential scanning calorimetry (DSC). The water-swollen hydrogels exhibited electroresponsiveness as shrinking and expanding reversibly with the on-off switching of the electric field in an electrode contact system. The magnitude of hydrogels' deswelling increased with the increase in the degree of swelling and applied voltages. This dehydration phenomenon was induced by the decrease in hydration power of microcounter ions due to the interaction with the electrodes by water electrolysis. The hydrogels were proved to be capable of generating a reasonable water flux of 2.76 Lm(-2) h(-1) (LMH) from brackish water (2000 ppm NaCl solution) due to their high swelling pressure. In addition, the water flux was affected by the amount of hydrogel particles on the membrane surface. Importantly, the prepared hydrogels could effectively release around 71% of the adsorbed water at an applied voltage of 15 V for 40 min, and were able to maintain their water flux and water recovery performances up to three times regeneration. Results indicate that the electric field is an attractive alternative stimulus for extracting desirable water from the hydrogel draw agent in the FO desalination process.