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In this study, DDR membranes with a layer thickness of approximately 700 nm were studied for separation feeds comprising mixtures of CO 2 and CH 4. The membranes displayed the highest CO 2 over CH 4 permselectivity and CO 2 permeability reported in literature. This was ascribed to a defect-free and ultra-thin zeolite film as well as an open and highly permeable support. For equimolar mixtures, the highest CO 2 over CH 4 permselectivity of 727 was observed when the pressure at the feed side was 5 bar(a) and the permeate pressure was 1 bar(a) at 25 °C. At these conditions, the CO 2 permeability was very high at 45 × 10−7 mol/(m2 s Pa). Separation experiments for 80/20 and 20/80 mixtures were also performed, and in these cases, CO 2 over CH 4 permselectivities of 1011 and 622 were observed, respectively. For all feeds, the membrane permselectivity decreased slightly at higher temperature and in all cases, higher permselectivity was observed when vacuum was applied at the permeate side. One-stage membrane processes for upgrading biogas to biomethane at three different operating pressures were designed based on the experimental data. In all cases, a quite low membrane area, methane slip and power need were observed. [Display omitted] • DDR membranes with ultrahigh CO 2 permeance for CO 2 /CH 4 separation. • One-stage DDR membrane processes for biogas upgrading. • Low membrane area, CH 4 slip, and power use for these processes. [ABSTRACT FROM AUTHOR]

The removal of propane and heavier hydrocarbons (C 3+ ) from natural gas is an important part of natural gas upgrading. In the present work, ultra-thin MFI zeolite membranes with a thickness of 400 nm and an estimated Si/Al ratio of 152 were evaluated for separation of C 3 H 8 and n -C 4 H 10 from binary and ternary mixtures with CH 4 . The membranes were selective towards the heavier hydrocarbons and showed high permeance at all investigated temperatures. At room temperature, the n -C 4 H 10 /CH 4 separation selectivity was 25, coupled with an n -C 4 H 10 permeance of 31 × 10 −7 mol m −2 s −1 Pa −1 for a 10/90 n -C 4 H 10 /CH 4 binary feed mixture. As the temperature was decreased to 281 K, the separation selectivity increased to as high as 55 with an n -C 4 H 10 permeance of 25 × 10 −7 mol m −2 s −1 Pa −1 . The separation selectivities for a 10/90 C 3 H 8 /CH 4 binary mixture were 9.5 and 19, with C 3 H 8 permeances as high as 54 and 37 × 10 −7 mol m −2 s −1 Pa −1 at 297 and 271 K, respectively. The higher selectivities observed for n -C 4 H 10 containing mixtures was ascribed to stronger adsorption of n -C 4 H 10 than C 3 H 8 in MFI, thus resulting in higher adsorption selectivities of the n -C 4 H 10 containing mixtures over CH 4 . For a 10/10/80 n -C 4 H 10 /C 3 H 8 /CH 4 ternary mixture, the highest sum selectivity of ( n -C 4 H 10 + C 3 H 8 )/CH 4 was 48 and the corresponding sum permance of ( n -C 4 H 10 + C 3 H 8 ) was 26 × 10 −7 mol m −2 s −1 Pa −1 at 283 K, which were similar to the separation results of n -C 4 H 10 /CH 4 binary mixture at the same conditions. The n -C 4 H 10 /CH 4 and C 3 H 8 /CH 4 separation selectivities from the ternary mixture were of course lower, but still as high as 32 and 16 at 283 K, with n -C 4 H 10 and C 3 H 8 permeances of 17 and 8 × 10 −7 mol m −2 s −1 Pa −1 , respectively. The results show that ultra-thin MFI zeolite membranes are promising candidates for separation of C 3+ hydrocarbons from natural gas. [ABSTRACT FROM AUTHOR]

We developed a series of molecule-scale hybrid amine-silica membranes synthesized from organoalkoxysilane precursors of 3-(triethoxysilyl)propan-1-amine (PA-Si) and 3-(triethoxysilyl)-N-methylpropan-1-amine (SA-Si), and made these functional using either unhindered amines or a 3-(triethoxysilyl)-N,N-dimethylpropan-1-amine (TA-Si) that is sterically hindered. CO 2 adsorption-desorption measurements of amine-silica powdered xerogels were conducted to observe the effect of amine type on CO 2 adsorption and desorption/diffusion properties. The results revealed that TA-Si xerogel powders demonstrated faster kinetics for both adsorption and desorption processes compared with those of the PA-Si and SA-Si samples due to the steric hindrance effect of the amine, which reduced the CO 2 binding energy and thereby boosted both the forward and reverse reaction rates of CO 2 -amine. In single-gas permeation performances, all the membranes exhibited excellent molecular sieving at higher temperatures and all the gases considered, except CO 2 , tended to permeate the membranes via activated diffusion. The effect of amine type on CO 2 separation performance was compared using CO 2 permeance, CO 2 /N 2 selectivity, activation energy for permeation ( E p ) of CO 2 [ E p (CO 2 ) ], and differences in E p between CO 2 and N 2 [ E p (CO 2 )-E p (N 2 ) ]. The TA-Si membrane demonstrated superior CO 2 separation performance, and achieved the highest values for both CO 2 permeance and selectivity. A relatively smaller difference in CO 2 separation performance was observed between PA-Si and SA-Si membranes despite some differences in basicity. This suggests that, rather than the basicity, it was the steric hindrance effect that played the greatest role in CO 2 transport performance across amine-silica membranes. [ABSTRACT FROM AUTHOR]

The recovery of light hydrocarbons such as propylene and ethylene from vent streams in polymer plants is desirable since it opens up for more efficient conversion of the monomers with high economic value. Consequently, polymer membrane vapour-gas separation systems have been used for this purpose for decades [1,2]. However, an alternative is zeolite membranes. In this work, ultra-thin MFI zeolite membranes (0.5 µm) were used to separate propylene or ethylene from binary 20/80 olefin/nitrogen mixtures at different temperatures. The membranes were olefin selective with high permeance at all investigated temperatures. At room temperature, the permeance of propylene was 22×10 −7 mol m −2 s −1 Pa −1 and the separation factor was 43, which corresponds to a separation selectivity of around 80. For a mixture of 20 mol% ethylene in nitrogen, the maximum separation factor was 6 (corresponds to a separation selectivity of 8.4) at 277 K with an ethylene permeance of 57×10 −7 mol m −2 s −1 Pa −1 . The membrane selectivity was governed by more extensive adsorption of olefin, especially propylene, as compared to nitrogen. Comparing with ethylene, propylene has higher heat of adsorption, which probably caused the higher propylene/nitrogen selectivity compared to ethylene/nitrogen selectivity. The permeance and the selectivity for propylene were much higher than for commercial polymeric membranes. For ethylene, the permeance was much higher, and the selectivity was comparable to commercial polymeric membranes. Modelling showed that the pressure drop over the support limited the flux through the membranes especially at higher temperatures and in particular for the ethylene/nitrogen system with high flux. Further, modelling indicated that the result obtained at high temperatures, where the flux was high, was also affected by concentration polarization. However, for the propylene/nitrogen system at the optimum separation temperature, the pressure drop over the support and the concentration polarization were small. The results show that ultra-thin MFI zeolite membranes are promising candidates for light olefins/nitrogen separation in polymer plants. [ABSTRACT FROM AUTHOR]

A novel strategy to modify the dense framework from different types of amine-functionalized organosilica membranes has been successfully applied via nickel-coordination to induce the formation of microporous membranes. Prior to the nickel-coordination reaction, aminosilica sols were prepared via hydrolysis of several types of amine precursors: bis [3-(trimethoxysilyl) propyl] amine (BTPA), trimethoxy [3-(methyl amino) propyl] silane (MAPTS), and 3-aminopropyl triethoxy silane (APTES). The optimal nickel/amine mole ratio was established within a range from 0 to 0.50 mol mol−1, and calcinations of the membranes were performed at 250, 300, and 350 °C. We found that nickel doping restructured the aminosilica network via a coordination bond, which then increased both the rigidity of the organic chain and the surface area of the resultant materials on the order of nickel-doped bis [3-(trimethoxysilyl) propyl] amine (Ni-BTPA) > nickel-doped 3-aminopropyl triethoxy silane (Ni-APTES) > nickel-doped trimethoxy [3-(methyl amino) propyl] silane (Ni-MAPTS). Spectroscopy characterization studies such as Ultraviolet–visible (UV–vis), Fourier Transform Infrared (FT-IR), and X-ray Diffraction (XRD) along with micropore analysis of N 2 sorption isotherms revealed that the formation of a coordinated network could be sterically hindered by the existence of non-hydrolyzable methyl groups on the pendant chain. The prepared composite membranes were utilized for the pervaporation of various types of organic mixtures for a composition ratio of methanol/solvents of 10/90 wt% at 50 °C. All nickel-composite membranes showed high flux and outstanding performance for the pervaporation of methanol/dimethyl carbonate (MeOH/DMC) and methanol/toluene (MeOH/Tol) mixtures. Ni-BTPA membranes with bridge-structured secondary-amine ligands recorded values for the flux that reached as high as 1.42 kg m−2 h−1 with an optimum separation factor for MeOH/Tol of 5,000. [Display omitted] • Hybrid nickel-doped aminosilica membranes were modified via bridge and pendant structure. • Nickel doping restructured the aminosilica network, resulting in higher rigidity and porosity. • The effect of nickel/amine mole ratio and calcination temperature were studied. • New formed subnanopores and the excess of nickel facilitated the diffusion of methanol. • Bridge-aminosilica structure gives the best pervaporation performance. [ABSTRACT FROM AUTHOR]

Abstract: Graphene and its derivatives have got numerous exciting applications due to the monolayer of tightly packed carbon atoms that possess many interesting properties. In this work, as-prepared graphene oxide (GO) was modified by hyperbranched polyethylenimine (HPEI) and then blended into polyethersulfone (PES) casting solution to prepare PES ultrafiltration membrane via phase inversion method. GO and its modified products were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The morphology and performance of the hybrid membranes were characterized by scanning electron microscopy (SEM), TEM, water contact angle, permeation measurement, mechanical measurement, antifouling and antibacterial tests. Mechanical tests revealed that the hybrid membranes exhibited a higher tensile strength and Young's modulus. The hybrid membranes exhibited a slightly lower pure water flux compared with pure membranes; however, the antifouling tests revealed that the hybrid membranes blended with HPEI-GO nanosheets displayed a preferable antifouling performance. The antibacterial tests confirmed that the as-formed hybrid membranes showed an effective antibacterial performance against Escherichia coli (E. coli). [Copyright &y& Elsevier]

In the present work, single channel tubular zeolite CHA membranes with a length of 50 cm and a membrane area of 100 cm2 were evaluated by SEM and permeation experiments with single components and industrially relevant humid mixtures. The membranes comprised well-intergrown and smooth CHA films with a thickness of <500 nm supported on the inside of a highly porous tube. For single component permeation, a very low SF 6 permeance of 4.5 × 10−10 mol/(m2‧s‧Pa) was observed, which indicated nearly defect free membranes. On the contrary, the membranes displayed a very high CO 2 permeance of 128 × 10−7 mol/(m2‧s‧Pa), which illustrated the very high permeability of the CHA pores. Finally, the membranes displayed excellent selectivity for separation of industrially relevant CO 2 /CH 4 /H 2 O mixtures, which was attributed to selective interaction between the CO 2 molecules and the polar water molecules in the pores. The highest observed CO 2 /CH 4 separation selectivity was as high as 198 in combination with a CO 2 permeance of 14 × 10−7 mol/(m2‧s‧Pa) at a feed pressure of 600 kPa (including 2.2 kPa water) and 293K. The corresponding CO 2 flux was 0.39 mol/(m2‧s) and the corresponding CO 2 /CH 4 separation factor was 162. The observed membrane performance was reduced by concentration polarisation due to the limited feed flow in the experimental setup. The corresponding selectivity and CO 2 permeance corrected for concentration polarisation were as high as 236 and 16 × 10−7 mol/(m2‧s‧Pa), and the corrected CO 2 flux was 0.44 mol/(m2‧s) and corrected separation factor was 198. An estimate showed that even at a low feed pressure of 500 kPa, it would be sufficient with as few as 64 membranes for processing of a feed of 100 Nm3/h raw biogas, i.e. the capacity of a typical biogas plant at a large farm, to biomethane with high purity. These results illustrated that the membranes are promising candidates for industrial separation of CO 2 from e.g. natural gas and biogas. [Display omitted] • The first report described industrially relevant CHA membranes. • The membrane was a single channel tube with a membrane area of 100 cm2. • CO 2 single gas permeances was as high as 128 × 10−7 mol/(m2‧s‧Pa). • The highest observed CO 2 /CH 4 separation factor was 169. • Effect of concentration polarisation on separation was discussed. [ABSTRACT FROM AUTHOR]

In the present work, ultra-thin MFI zeolite membranes prepared in fluoride media were evaluated for separation of equimolar CO 2 /H 2 gas mixtures. Both dry and humid mixtures were evaluated. For dry gas mixtures, the membrane selectivity increased from 13 to 45 when the temperature decreased from 318 to 285 K, and CO 2 flux was very high and almost constant at 4 mol m−2 s−1, corresponding to CO 2 permeance of 100 × 10−7 mol m−2 s−1 Pa−1 (29851 GPU). For humid gas mixtures with a partial pressure of water of 3.5 kPa, the CO 2 flux decreased from 3.27 to 0.10 mol m−2 s−1 when the temperature decreased from 316 to 288 K. The corresponding CO 2 permeance decreased from 79 to 2.5 × 10−7 mol m−2 s−1 Pa−1 (from 23582 to 746 GPU). At the highest temperature 318 K, the CO 2 /H 2 separation selectivity was slightly higher for the humid gas mixture. For the humid gas mixture, the CO 2 flux increased from 3.27 to 3.76 mol m−2 s−1 at 318 K and from 0.52 to 0.90 mol m−2 s−1 at 296 K when the permeate pressure was reduced from atmospheric to vacuum, respectively. The separation selectivity of CO 2 /H 2 was almost not affected by the permeate pressure. The results show that ultra-thin fluoride MFI zeolite membranes are promising candidates for separation of CO 2 from dry or humid synthesis gas. Image 1 • Ultra-thin fluoride MFI membranes were evaluated for separation of CO 2 from H 2. • Separation experiments were performed for both dry and humid gas mixtures. • A selectivity of 45 and a CO 2 flux of 4 mol m−2 s−1 were observed for dry gas mixtures. • The maximum observed CO 2 permeance was 100 × 10−7 mol m−2 s−1 Pa−1. • The membranes show hydrophobicity for separation of humid gas mixture. [ABSTRACT FROM AUTHOR]

Ceramic microfiltration membranes with superior chemical and mechanical stability for sustainable operation under harsh conditions have demonstrated great potential for industrial wastewater treatment. In this study, low-cost ceramic microsheet membranes with a thickness of sub-0.5 mm that possess superhydrophilic and underwater superoleophobic properties were fabricated from an Al 2 O 3 -rich Al 2 O 3 /polysulfone composite slurry via a phase inversion/sintering strategy. The cross-sectional morphologies of these phase inversion-induced composite films appear as ceramic green bodies that can be precisely controlled by tuning the operation parameters during the classic phase-inversion process of a polymer, which allows the morphology to withstand a subsequent high-temperature (1250 °C) sintering process. The thinner nature (<0.5 mm), suitable pore size (~100 nm), and a superior wetting chemistry make these ceramic microsheets very promising for the separation of oil-in-water emulsions with an outstanding separation efficiency of >99% and a much higher emulsion permeability of ~3,000 L/(m2 h bar), which is 2 orders of magnitude higher than most commercially available microfiltration membranes that are capable of similar levels of separation performance. This process resulted in a favorable membrane that combines robustness under complex chemical environments with low cost for both materials and processing approaches, which should facilitate its practical application in the industrial treatment of oily wastewater. Image 1 • Low-cost, ceramic microsheet membranes with a thickness of sub-0.5 mm were developed. • The cross-sectional morphologies of the microsheets can be tailored via a phase inversion/sintering process. • The microsheets demonstrated superhydrophilic and underwater superoleophobic properties. • The microsheets demonstrated outstanding separation properties for oil/water emulsions. [ABSTRACT FROM AUTHOR]

Highly permeable and selective tubular zeolite CHA membranes with a thickness of about 450 nm and a length of 100 mm and an inner diameter of 7 mm were evaluated by single gas permeation experiments and for separation of an equimolar CO 2 /CH 4 mixture. The membranes displayed high H 2 and CO 2 single gas permeances of 55 × 10−7 mol m−2 s−1 Pa−1 and 94 × 10−7 mol m−2 s−1 Pa−1, respectively, and a very low SF 6 permeance of 3 × 10−9 mol m−2 s−1 Pa−1. The highest observed mixture separation factor was 99 with CO 2 permeance of 60 × 10−7 mol m−2 s−1 Pa−1 at a feed pressure of 5 bar and permeate pressure of 0.12 bar. The corresponding CO 2 flux was 1.46 mol m−2 s−1. The highest observed flux was 1.98 mol m−2 s−1 with a separation factor of 52 at a feed pressure of 10 bar and permeate pressure of 0.12 bar at room temperature. To the best of our knowledge, this is the first report describing highly permeable and selective tubular CHA membranes. The results indicate that the membranes have a great potential for industrial separation of CO 2 from natural gas and biogas. • CO 2 /CH 4 were separated on highly permeable and selective tubular CHA membranes. • Single gas CO 2 and SF 6 permeances were 94 × 10−7 and 3 × 10−9 mol m−2 s−1 Pa−1. • Vacuum was used on the permeate side for separation. • The highest observed separation factor was 99. • Separation results were explored by modelling. [ABSTRACT FROM AUTHOR]

Membrane-based technology has garnered significant interest in the separation and purification of molecules due to its inherent advantages, such as high efficiency, low energy consumption, and ease of operation. In this study, rigid-flexible coupled organosilica membranes were fabricated through co-polymerization using 1,2-bis(triethoxysilyl)acetylene (BTESA) containing rigid acetylene bridges and 1,2-bis(triethoxysilyl)propane (BTESP) containing flexible propane bridges. The incorporation of flexible propane bridges into BTESA networks allowed for precise adjustment of the network structures, resulting in composite BTESA-P membranes with improved molecular sieving properties. BTESA-P membrane demonstrated significant promise for applications in both CO 2 capture and pervaporation (PV) dehydration due to its high potential. BTESA-P30 membrane, fabricated using the rigid-flexible coupled strategy, demonstrated a CO 2 permeance of 3807 GPU and a CO 2 /N 2 selectivity of approximately 40. These results surpassed those of numerous previously reported membranes, indicating significant potential for CO 2 capture applications. BTESA-P30 membrane exhibited significant competitiveness in the decarbonization process of natural gas. More significantly, analogous occurrences are evident in gas permeation and PV separation process, where the permeation mechanism of gas and PV separation is primarily governed by molecular sieving. The utilization of diverse organosilica precursors in the rigid-flexible coupled strategy proposed in this study offers increased potential for membrane structure design and energy-efficient separation of molecules. [Display omitted] • Rigid-flexible coupled organosilica membranes were fabricated. • BTESA-P membranes were endowed with enhanced sieving properties. • Rigid-flexible coupled strategy exhibited great potential for high-performance membranes design. [ABSTRACT FROM AUTHOR]

The abatement of defects in zeolite membranes is essential for achieving high selectivity. In the present work, a simple and effective method for blocking defects in ultra-thin (ca. 0.5 μm) MFI zeolite membranes has been developed. The method is based on deposition of an ultra-thin (~15 nm) layer of amorphous silica on the top surface of the membrane. Permporometry data indicated that the amount of defects, especially defects larger than 4 nm, in the membranes was significantly reduced after the modification. In mixture separation experiments, the CO 2 /H 2 separation factor increased dramatically after blocking the defects in a defective membrane that was selected for the experiments. For instance, at 263 K and 9 bar feed pressure, the CO 2 /H 2 separation factor increased from 8.5 to 36 after modification of the membrane, whereas the CO 2 flux only decreased by ca. 40%. [ABSTRACT FROM AUTHOR]

Surface barriers are influencing the mass transfer in nanopores, but their origin is unclear and can be quite different in different materials. For MFI and CHA membranes studied here, we show that the surface barrier may be a surface diffusion process with higher activation energy than the surface diffusion process in the pores, but other possible mechanisms such as pore blocking and pore narrowing has not been ruled out. The higher activation energy is probably a result of less interaction between adsorbed molecules at the pore mouth than inside the pores, i.e. the barrier is simply a geometrical effect in these materials. For pure components at low concentration in MFI zeolite, we found that barrier is proportional to the product of the molecular weight and heat of desorption. For MFI and CHA zeolite, we observed that the barrier is a function of concentration and approach zero at high concentration and that the barriers of the components become more similar due to interaction between the components in mixtures, which explains the high and selective mass transfer displayed by these nanoporous materials at high concentration. [Display omitted] • The surface barrier is a surface diffusion process with high activation energy. • The MFI surface permeability inversely proportional to M w and ΔH ads. • More similar surface permeabilities in mixtures, which results in high selectivity. [ABSTRACT FROM AUTHOR]

Sol-gel-derived organosilica membranes with different linking groups consisting of 2 carbon atoms (ethane, ethylene, and acetylene) were fabricated using bis(triethoxysilyl)ethane (BTESE), bis(triethoxysilyl)ethylene (BTESEthy), and bis(triethoxysilyl)acetylene (BTESA). No research group has ever proposed tailoring the microstructure and permeation properties of bridged organosilica membranes as a way to control the bond angles. In this study, however, we found that increases in the Si–O–Si and Si–C–C bond angles contributed to the formation of a loose and uniform structure, which was suggested by the blue shift of Si–O–Si and Si–C–C bonds in the FT-IR spectra. BTESA membranes featured a more open and accessible pore structure, which was suitable for the separation of C 3 H 6 /C 3 H 8. The present study provides a novel way to design the microstructure and permeation properties of organosilica membranes via controlling the bond angles in the network structure. Image 1 • Microstructure of organosilica membranes can be tailored via controlling the bond angles. • BTESA membrane shows great potential prospect in C 3 H 6 /C 3 H 8 separation. • This study provides a novel strategy to design the structure of membranes for specific separation system. [ABSTRACT FROM AUTHOR]

Membrane-based separation of organic/organic mixtures is of great importance in the chemical and petrochemical 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 prepared, 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 °C. This impressive performance was primarily the result of the preferential 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 membranes, 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 organosilica membranes for high-performance organic/organic pervaporation. Image 1 • The first use of organosilica membrane for organic/organic pervaporation. • The as-prepared BTESA membranes were highly reproducible with novel organic tolerance. • A generalized SD model aptly described the PV performance of the BTESA membranes. • BTESA membranes enabled rapid and efficient removal of methanol from methanol/DMC. [ABSTRACT FROM AUTHOR]

The separation of azeotropic mixtures such as methyl acetate and methanol via a membrane is an interesting and challenging issue, since the membrane must be able to withstand these harsh solvents and provide good flux and selectivity. SiC-based membranes have attracted a great deal of interest due to their high mechanical strength, structural stability, and corrosion resistance at elevated temperatures. Herein, we describe the first use of polytitanocarbosilane (TiPCS), which is known as a precursor of continuous Si–Ti–C–O fibers (Tyranno), in the preparation of Ti-incorporated SiC-based membranes for the pervaporation (PV) removal of water or methanol, and describe the evaluation of hydrothermal stability. For this study, the physical and chemical properties of TiPCS-derived materials during pyrolysis were characterized via TG-MS, ATR-FTIR, XPS, XRD, and N 2 adsorption-desorption isotherms. The pore characteristics and surface areas of TiPCS-derived ceramic powders revealed that the titanium components in TiPCS inhibit and/or reduce the densification of the network structures at elevated temperatures. The network structure of TiPCS-derived, SiC-based membranes showed trends similar to those of TiPCS-derived ceramic powders. The membrane prepared at 750 °C featured reproducibility and attractive selectivities for the PV removal of water or methanol from liquid mixtures. Figure. Schematic illustration of the conversion process for a TiPCS membrane. Image 1 • The first fabrication of novel Ti-incorporated SiC-based membranes derived from polytitanocarbosilane. • Evolution of the network structure in polytitanocarbosilane during pyrolysis is discussed. • Sub-nanoporous SiC-based membranes displayed high performance for both gas and pervaporation separation. • TiPCS membranes exhibited high separation performance for methanol/methyl acetate mixtures. [ABSTRACT FROM AUTHOR]

We developed a procedure that saves significant amounts of energy during the separation of organic liquids via organic solvent reverse osmosis (OSRO). The proof-of-concept was confirmed using theoretical calculation to demonstrate energy-consumption at less than 1/100th and 1/10th that of conventional distillation and pervaporation (PV), respectively. Bis(triethoxysilyl)acetylene (BTESA)-derived organosilica membranes consisting of a SiO 2 –ZrO 2 intermediate layer and an α-Al 2 O 3 support were evaluated by challenging a series of azeotropic mixtures of methanol/toluene, methanol/methyl acetate, methanol/dimethyl carbonate (DMC), and methanol/methyl tert-butyl ether (MTBE). BTESA membranes showed excellent size- and/or shape-sieving properties and remarkable levels of organic-tolerance with an ultrahigh methanol flux that outperforms state-of-the-art polymeric membranes. In particular, the robust ceramic support and rigid organosilica networks endowed the resultant membranes with the ability to withstand transmembrane pressures as high as 18 MPa. Image 1 • Organic solvent reverse osmosis enables substantial decrease in energy consumption. • Organosilica membrane is proposed for organic solvent reverse osmosis. • BTESA membrane exhibits novel molecular sieving property and organic tolerance. • BTESA membrane could withstand a transmembrane pressure up to 18 MPa. [ABSTRACT FROM AUTHOR]

Abstract: Sodium 4-styrenesulfonate was grafted onto the surfaces of halloysite nanotubes (HNTs) via surface-initiated atom transfer radical polymerization (SI-ATRP), and then negatively charged nanofiltration (NF) membranes were fabricated by blending various contents of HNTs-poly(sodium 4-styrenesulfonate) (HNTs-poly(NASS)) composites via phase inversion method. The grafting degree was effectively controlled by varying the reaction time and the amount of monomers. The results of FT-IR, TGA, and TEM indicated that HNTs-poly (NASS) composites were successfully synthesized and GPC results exhibited the linear relationship between number-average molecular mass (Mn) and reaction time. In addition, the membranes were characterized by SEM, static water contact angle and water ratio. It was found that the hydrophilicity of hybrid membranes was significantly superior to bare PES membranes, which corresponded to the results of pure water flux and thus may enhance fouling resistance to a certain extent. The ion-exchange capacity (IEC) value could be up to 0.07mmol/g when the HNTs-poly (NASS) content was only 3wt%. Meanwhile, the pure water flux of the hybrid membranes increased with increasing the HNTs-poly (NASS) content. The permeation ratio for saline solution increased significantly, such as from 77% to 96.5%. From the analysis above, these prepared hybrid membranes have a potential application in desalination of textile industry and wastewater treatment. [Copyright &y& Elsevier]

The evolution of the physicochemical properties of allylhydridopolycarbosilane (AHPCS) was systematically investigated via DLS, TG, FTIR, XRD, and EDS. AHPCS-derived membranes were prepared by coating AHPCS sols onto porous substrates, which was then followed by pyrolysis at 300–800 °C. The pre-crosslinking by thermal curing significantly increased the colloidal sol size of AHPCS in toluene solutions, which effectively reduced penetration into substrates and enhanced the gas permeation. Furthermore, the pore structure of AHPCS-derived membranes could be precisely tailored by the pyrolysis temperatures, and the results indicated that the structure of membranes could be roughly classified into one of three types: a dense polymer structure, a loose transitional structure, and a denser ceramic structure (here, the term 'dense/denser' refers to the small/smaller pore structure, while the 'loose' refers to the large pore structure). AHPCS-derived membranes prepared at 300–800 °C under a N 2 flow displayed superior H 2 permeance of (0.2–5) × 10−6 mol/(m2 s Pa) at 200 °C with good H 2 /N 2 selectivity of 12–56. Ceramic SiC membranes prepared at 700 °C showed an attractive H 2 permeance of (2–4) × 10−6 mol (m2 s Pa)−1 at 200 °C with H 2 /N 2 selectivity of 16–22, H 2 /SF 6 selectivity higher than 10,000, and N 2 /SF 6 selectivity higher than 800. Moreover, the structure of the ceramic SiC membranes was highly stable with good oxidation resistance at 500 °C under air. AHPCS membranes prepared at 300–800 °C had different pore structures that exhibited a high level of quality and a variety of permeation properties that could provide many options for membrane materials over a wide range of applications. Schematic illustration for the evolution of the network structure for AHPCS pyrolyzed at different temperatures. Image 1 • The microstructures of the AHPCS-derived membranes were precisely tailored via control of the pyrolysis temperatures. • The pre-crosslinked AHPCS effectively reduced the penetration into substrates and enhanced the permeation. • Ceramic SiC membranes showed good oxidation resistance at 500 °C under air. • AHPCS membranes prepared at 300–800 °C with different pore structures have excellent gas permeation properties. [ABSTRACT FROM AUTHOR]

Membrane-based separation technologies are considered an effective process for the capture of CO 2 due to advantages such as high levels of energy efficiency with inexpensive levels of investment. It remains challenging, however, to develop a membrane with high levels of both permeance and selectivity with the ability to capture CO 2 in a highly efficient manner. Herein, we report amino-decorated organosilica membranes that are based on a facile and effective co-polymerization strategy that uses bis(triethoxysilyl)acetylene (BTESA) and (3-aminopropyl) triethoxysilane (APTES) precursors. This co-polymerization strategy simultaneously endows the resultant membranes with a controlled pore size and enhanced CO 2 -philic properties that have significantly improved CO 2 separation performance. These composite membranes display CO 2 permeance that ranges from 2550–3230 GPU and a range for CO 2 /N 2 selectivity of 31–42 in the separation of CO 2 /N 2 mixtures, which outperforms most state-of-the-art membranes and exceeds the target for post-combustion CO 2 capture operations. A satisfying performance was achieved with a CO 2 permeance of 8 ✕ 10−7 mol m−2 s−1 Pa−1 (2390 GPU) and CO 2 /CH 4 selectivity of 70. The present study highlights an elegant decoration strategy for the production of membranes with ultrahigh CO 2 capture capacities, which can also be extended to other organosilica precursors for target-oriented separations by varying the bridged or side-chain groups. Image 1 • Amino-decorated organosilica membrane was prepared via co-polymerization strategy. • BTESA-A membranes obtained controlled pore size and enhanced CO 2 affinity. • BTESA-A membranes featured promisingly high CO 2 capture performance. [ABSTRACT FROM AUTHOR]

Membrane-based separation techniques are responsible for great advances in the separation of propylene/propane mixtures. In this study, bis(triethoxysilyl)acetylene (BTESA) was selected as the precursor in the fabrication of organosilica membranes for use in propylene/propane separation. We proposed an effective strategy to finely engineer the pore subnano-environment of BTESA membranes for highly selective propylene/propane separation via controlling the calcination temperatures. Measurement of the surface energy, the 29Si-NMR spectra, and the gas sorption isotherms clearly indicated that low-temperature calcined BTESA materials with a greater number of silanol groups showed an enhanced affinity to propylene molecules. BTESA membranes calcined at 150 °C featured a promisingly high C 3 H 6 /C 3 H 8 selectivity of 52 and a C 3 H 6 permeance of 1.7 ✕ 10−8 mol m−2 s−1 Pa−1 at 50 °C. These values were approximate to those reported for ZIF-8 membranes and higher than the standards for commercialization. The high level of C 3 H 6 /C 3 H 8 separation performance was believed to be accounted by the synergetic effects of both controlled pore size and enhanced affinity to propylene molecules. Moreover, compared with traditional organosilica membranes that were calcined at ~350 °C, low-temperature calcination (150 °C) for BTESA membranes efficiently reduced the energy consumption and fabrication cost. Image 1 • Firing conditions engineered pore subnano-environment of organosilica membranes. • Silanol groups accelerated the permeation of C 3 H 6 molecules. • BTESA-150 membranes featured promisingly high C 3 H 6 /C 3 H 8 separation performance. [ABSTRACT FROM AUTHOR]