Effect of operation conditions in the pervaporation of ethanol–water mixtures with poly(1‐trimethylsilyl‐1‐propyne) membranes

Poly(1‐trimethylsilyl‐1‐propyne) (PTMSP) is known to show preferential permeation of ethanol in the pervaporation of ethanol–water mixture. Although this polymer presents good characteristics for the separation of organic–water solutions, operation conditions and membrane characteristics, such as thickness, affect its pervaporation performance. The effect of temperature and feed concentration on pervaporation was studied. During pervaporation of 10 wt % ethanol–water solution, the separation factor (α_H2O^EtOH) remains almost constant, whereas the permeation flux (F) increases exponentially with operation temperature. On the other hand, the separation factor decreases, whereas the permeation flux increases with ethanol content in the feed mixture. The membrane thickness also affects the performance of PTMSP polymer films: selectivity increases sharply with membrane thickness up to 50 μm, whereas it remains constant for thicker membranes. The permeation flux decreases with membrane thickness in the whole range studied. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94:1395–1403, 2004     

改善无机填料混合基质膜气体分离性能的研究进展

混合基质膜（MMMs）是结合了无机填料和有机基质特点的一类膜材料,因其在气体分离应用上具有良好的渗透通量和分离性能被广泛关注。无机填料诸如二氧化硅纳米颗粒球、沸石分子筛、金属有机框架（MOF）、氧化石墨烯（GO）、碳纳米管（CNT）均被广泛应用于混合基质膜的制备,但是碍于无机填料在有机相中的分散性问题、两相相容性问题和界面缺陷问题,常会导致较差的气体分离性能。针对近年通过对无机填料进行表面官能化修饰、共价交联、多元填充、调控形貌等来改善混合基质膜气体分离性能的研究进行总结和阐述,并对其未来的发展趋势进行了展望。     

APTES改性ZIF-L/PEBA混合基质膜强化渗透汽化分离苯酚研究

渗透汽化(PV)膜分离是一种高效节能、无污染的化工分离技术,在有机废水处理领域的应用潜力巨大。以3-氨丙基三乙氧基硅烷(APTES)改性二维ZIF-L(AZLs),将其引入聚醚嵌段酰胺(PEBA)内制备AZLs/PEBA混合基质膜,用于分离水溶液中的苯酚。系统表征了所制膜的微结构与物化特性,考察了APTES添加量、AZLs填充量、操作温度、料液浓度等对膜分离性能的影响。结果表明：AZLs均匀分散在PEBA基质中,表明两者具有良好的界面相容性。AZLs的加入使得膜疏水性增强而表面自由能降低,从而提高了PEBA膜的选择性。当分离80℃、1000 mg/kg苯酚水溶液时,AZLs/PEBA膜总通量可达2046 g/(m²·h),分离因子为25.4,并且具有一定的稳定性。所制AZLs/PEBA混合基质膜在含酚废水处理方面具有应用前景。     

Separation of phenol–water mixture by membrane pervaporation using polyimide membranes

Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol–water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 822–829, 2002     

Fabrication of Pebax/SAPO mixed matrix membranes for CO2/N2 separation

Mixed matrix membranes (MMMs) were prepared by solvent evaporation method using Pebax-1074 polymer as matrix and inorganic zeolite SAPO-23 as dopant. The morphology, surface functional groups, microstructure, thermal stability, and separation performance of MMMs were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and gas permeation, respectively. The effects of dopant loading amount, permeation temperature, and permeation pressure on the structure and properties of MMMs were investigated. The results showed that the introduction of SAPO zeolite reduced the crystallinity of the MMMs and improved the CO₂/N₂ selectivity. Under the conditions of 30°C and 0.15 MPa, the MMMs prepared by incorporating with 5% SAPO zeolite in content exhibited the highest CO₂/N₂ selectivity of 72.0 together with the CO₂ permeability of 98.2 Barrer.     

Separation properties of alcohol–water mixture through silicalite-I-filled silicone rubber membranes by pervaporation

The structure and the adsorption–desorption properties of zeolite silicalite-I by different treatments after synthesis were studied. The pervaporation properties of the alcohol–water mixture through silicone rubber filled with zeolite silicalite-I by different treatments were also investigated. Treating silicalite-I by acid or/and under steam was found to eliminate the metallic impurities in the zeolite and to perfect the crystalline structure of the zeolite. After treatment, silicalite-I is more selective to alcohol and the desorption of the alcohol from the zeolite is also easier. The silicone rubber membrane filled with treated silicalite-I shows a high performance for alcohol extraction from the dilute aqueous solution by pervaporation. The separation factor of the poly(dimethyl siloxane) (PDMS) membrane filled with silicalite-I treated successively by acid and steam is about 30 when the ethanol content in the feed is 5 wt % at 50°C. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 629–636, 1998     

碳纳米管/环糊精金属有机骨架协同强化混合基质膜的CO2分离

为了实现混合基质膜中CO₂的高效分离,设计了羧基化多壁碳纳米管(CNT)和氨基化β-环糊精金属有机骨架(β-CD MOF)双填料(CM),并将其引入磺化聚醚醚酮(SPEEK)基质中,在膜内同时构建CO₂扩散通道和亲和位点,增强了混合基质膜的分离性能。采用FTIR和BET表征了CM的化学结构和孔结构,借助膜的SEM、FTIR和力学性能表征了填料-聚合物界面相互作用。研究了CM的合成比例、含量、压力、温度和混合气等因素对混合基质膜分离性能的影响。结果表明：CM与SPEEK之间具有良好的相容性并为气体分子提供了快速的传递通道。在改性CNT与MOF的质量比为5∶5、添加量为7%(质量)以及0.1 MPa和25℃的条件下,混合基质膜的分离性能最优,CO₂渗透性为844 Barrer,CO₂/N₂选择性为84,与纯SPEEK膜相比,分别提升了178%和163%,超过2019年上限。羧基化CNT的直孔通道缩短了CO₂的扩散路径,同时改性β-CD MOF表面的氨基载体提升了CO₂的溶解性,两者协同提高了混合基质膜的分离性能。此外,负载双填料的膜比单独负载相同含量的羧基化CNT或氨基化MOF的膜具有更好的分离性能。在360 h的测试过程中,混合基质膜保持较好的分离稳定性。     

碳纳米管/环糊精金属有机骨架协同强化混合基质膜的CO2分离

为了实现混合基质膜中CO₂的高效分离,设计了羧基化多壁碳纳米管(CNT)和氨基化β-环糊精金属有机骨架(β-CD MOF)双填料(CM),并将其引入磺化聚醚醚酮(SPEEK)基质中,在膜内同时构建CO₂扩散通道和亲和位点,增强了混合基质膜的分离性能。采用FTIR和BET表征了CM的化学结构和孔结构,借助膜的SEM、FTIR和力学性能表征了填料-聚合物界面相互作用。研究了CM的合成比例、含量、压力、温度和混合气等因素对混合基质膜分离性能的影响。结果表明：CM与SPEEK之间具有良好的相容性并为气体分子提供了快速的传递通道。在改性CNT与MOF的质量比为5∶5、添加量为7%(质量)以及0.1 MPa和25℃的条件下,混合基质膜的分离性能最优,CO₂渗透性为844 Barrer,CO₂/N₂选择性为84,与纯SPEEK膜相比,分别提升了178%和163%,超过2019年上限。羧基化CNT的直孔通道缩短了CO₂的扩散路径,同时改性β-CD MOF表面的氨基载体提升了CO₂的溶解性,两者协同提高了混合基质膜的分离性能。此外,负载双填料的膜比单独负载相同含量的羧基化CNT或氨基化MOF的膜具有更好的分离性能。在360 h的测试过程中,混合基质膜保持较好的分离稳定性。     

Fabrication of mixed‐matrix membranes with MOF‐derived porous carbon for CO2 separation

Mixed‐matrix membranes (MMMs) have shown great advantages but still face some challenges, such as the trade‐off between permeability and selectivity, stability, and the lack of efficient ways to enhance them simultaneously. Here, the fabrication of MMMs with metal‐organic frameworks derived porous carbons (MOF‐PCs) as fillers which exhibit selective‐facilitating CO₂ transport passage originating from interactions between fillers and CO₂ is showed. With the aid of the developed multicalcination method, MOF‐PCs with variable N‐contents were prepared and incorporated into PPO‐PEG matrix for the first time to prepare MMMs, which show excellent separation performance for CO₂/CH₄ mixture with a tunable separation performance by combining different N‐contents and surface areas of MOF‐PCs. Moreover, the developed MMMs have hydrothermal and chemical stability. This work not only presents a series of MMMs with both good separation properties and stability, it also provides useful information for guiding the fabrication of high performance MMMs for practical application. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3400–3409, 2018     

Poly(vinyl alcohol)/carboxyl graphene mixed matrix membranes: High-power ultrasonic treatment for enhanced pervaporation performance

High-power ultrasonic treatment was conducted during the mixing process to obtain poly(vinyl alcohol) (PVA)/carboxyl graphene (CG) mixed matrix membranes (MMMs). Results from X-ray photoelectron spectrometer and thermogravimetric analysis confirmed the enhanced esterification reaction. The increased amorphous region and free volume were investigated by wide-angle X-ray diffraction and positron annihilation lifetime spectroscopy. Scanning electron microscope and atomic force microscope measurements suggested that ultrasonic could uniformly disperse CG in PVA polymer matrix. The mechanical properties and hydrophilicity of as-prepared membrane were enhanced due to ultrasonic treatment. The permeation flux and separation factor of PVA/CG-US membrane for 90 wt % ethanol aqueous solution were 0.79 kg m⁻² h⁻¹ and 860, respectively. For methanol (15 wt %)/methyl tert-butyl ether mixture, its permeation flux and separation factor were also increased significantly compared with membranes without ultrasonic treatment. Due to the simplicity of the ultrasonic process and the versatility of the inorganic fillers, this method may contribute to the design of various MMMs and extend the application of these membranes in different uses. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48526.     

Separation of acid–water mixtures by pervaporation using nanoparticle filled mixed matrix copolymer membranes

BACKGROUND: Low energy and less expensive membrane based separation of acetic acid‐water mixtures would be a better alternative to conventional separation processes. However, suitable acid resistant membranes are still lacking. Thus, the objective of the present study was to develop mixed matrix membrane (MMM) which would allow high flux and water selectivity over a wide range of feed concentrations of acid in water. RESULTS: Three MMMs, namely PANBA0.5, PANBA1.5 and PANBA3 were made by emulsion copolymerization of acrylonitrile (AN) and butyl acrylate (BA) with 5.5:1 comonomer ratio and in situ incorporation of 0.5, 1.5 and 3 wt%, sodium montmorilonite (Na‐MMT) nanofillers, respectively. For a feed concentration of 99.5 wt% of acid in water the membranes show good permeation flux (2.61, 3.19, 3.97 kg m^?2 h^?1 µm^?1, for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) and very high separation factors for water (1473, 1370, 1292 for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) at 30 °C. Similarly for a dilute acid–water solution, i.e. for 71.6 wt% acid the membrane showed a very high thickness normalize flux (8.67, 9.44, 11.56 kg m^?2 h^?1 µm^?1, for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) and good water selectivity (101.7, 95.3, 79 for PANBA0.5, PANBA1.5 and PANBA3 membrane, respectively) at the same feed temperature. The permeation ratio, permeability, diffusion coefficient and activation energy for permeation of the membranes were also estimated. CONCLUSION: Unlike most of the reported membranes, the present MMMs allowed high flux and selectivity over a wide range of feed concentrations. These membranes may also be effective for separating other similar organic‐water mixtures. Copyright © 2012 Society of Chemical Industry     

Water–alcohol separation by pervaporation through poly(amide-sulfonamide)s (PASAs) membranes

Pervaporation membranes derived from seven homopolymers of poly(amide-sulfonamide)s (PASAs) were prepared by casting 10–17% polymer solutions of N,N-dimethylacetamide. The membranes were characterized by sorption experiments, scanning electron microscope, and wide-angle X-ray diffraction. During the pervaporation of 90 wt % aqueous solution of methanol, ethanol, 1-propanol, and 2-propanol, all membranes were preferentially permeable to water, and their separation factors were mainly dependent on the molecular weight of the solvent. The exact structure of the PASAs had a profound effect on their pervaporation characteristics. Polymeric membrane based on N,N′-bis(4-aminophenylsulfonyl)-1,3-diaminopropane and isophthaloyl chloride exhibited the best selectivity factor of 1984 for a 10 : 90 (by weight) mixture of water/ethanol at 20°C. However, the permeation rates of all materials for dehydration of 90 wt % ethanol were slow in a range of 6.6–34.4 g m⁻² h⁻¹. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1113–1119, 1997     

Size effects of graphene oxide on mixed matrix membranes for CO2 separation

Graphene oxide (GO)‐polyether block amide (PEBA) mixed matrix membranes were fabricated and the effects of GO lateral size on membranes morphologies, microstructures, physicochemical properties, and gas separation performances were systematically investigated. By varying the GO lateral sizes (100–200 nm, 1–2 μm, and 5–10 μm), the polymer chains mobility, as well as the length of the gas channels could be effectively manipulated. Among the as‐prepared membranes, a GO‐PEBA mixed matrix membrane (GO‐M‐PEBA) containing 0.1 wt % medium‐lateral sized (1–2 μm) GO sheets showed the highest CO₂ permeation performance (CO₂ permeability of 110 Barrer and CO₂/N₂ mixed gas selectivity of 80), which transcends the Robeson upper bound. Also, this GO‐PEBA mixed matrix membrane exhibited high stability during long‐term operation testing. Optimized by GO lateral size, the developed GO‐PEBA mixed matrix membrane shows promising potential for industrial implementation of efficient CO₂ capture. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2843–2852, 2016     

Poly(vinyl alcohol)/ZIF‐8‐NH2 mixed matrix membranes for ethanol dehydration via pervaporation

Ethanediamine‐modified zeolitic imidazolate framework (ZIF)‐8 particles (ZIF‐8‐NH₂) is synthesized and incorporated in the poly(vinyl alcohol) (PVA) matrix to fabricate novel PVA/ZIF‐8‐NH₂ mixed matrix membranes (MMMs) for pervaporation dehydration of ethanol. The PVA/ZIF‐8‐NH₂ MMMs exhibit enhanced membrane homogeneity and separation performance because of the higher hydrophilicity and restricted agglomeration of the particles, as compared to corresponding MMMs loaded with unmodified particles. The effect of ZIF‐8‐NH₂ loading in the MMMs is studied and the MMM with a 7.5 wt % ZIF‐8‐NH₂ loading shows the best pervaporation performance for ethanol dehydration at 40°C. Various characterization techniques (Fourier transform infrared, scanning electron microscope, contact angle, sorption test, etc.) are used to investigate the MMMs loaded with ZIF‐8 and ZIF‐8‐NH₂ particles. The impact of operation conditions on pervaporation performance is also performed. The performance benchmarking shows that the MMMs have superior separation factors and comparable flux to most other PVA hybrid membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1728–1739, 2016     

Butanol isomer separation using polyamide-imide/CD mixed matrix membranes via pervaporation

Mixed matrix membranes (MMMs) comprising polyamide-imide (PAI) and α-, β- or γ-cyclodextrin (CD) have been investigated experimentally and computationally for isomeric n-butanol/tert-butanol (n-BuOH/t-BuOH) separation via pervaporation. Consistent with molecular simulation, experimental results show that the CD inclusion ability and butanol discrimination ability are dependent on both CD cavity size and butanol molecular size. The PAI membrane incorporated with α-CD has the smallest cavity and has the highest discrimination ability for the n-BuOH/t-BuOH pair but with a low butanol flux. The mixed matrix membrane embedded with γ-CD has the lowest selectivity and the highest flux. The PAI/β-CD membrane has a comparable selectivity and flux, and exhibits preferential sorption and diffusion selectivity toward n-BuOH. A maximum separation factor of 1.53 with a corresponding flux of 4.4 g/m² h are obtained at an optimal β-CD loading of 15 wt%. Further increments in the CD content eventually lead to a decrease in separation performance because of CD agglomeration and severe phase separation. To better understand the influence of CD on the separation performance of mixed matrix membranes, SEM, FTIR and XRD have been employed for membrane characterizations. The effect of n-butanol/t-butanol ratio in the feed composition has also been studied. It is found that both flux and separation factor decrease with increasing n-butanol content in the feed. The decline is attributed to the change in total vapor pressure at the upstream and the mutual drag effect of isomeric butanol molecules.     

Facile preparation of Cu(I) impregnated MIL‐101(Cr) and its use in a mixed matrix membrane for olefin/paraffin separation

Cu(I) impregnated MIL‐100(Cr) [denoted Cu@MIL‐101(Cr)] is fabricated by a facile method and utilized in mixed matrix membranes (MMMs) for propylene/propane separation. Cu(I) is prepared from a CuCl₂ solution via mild reduction process using sodium sulfite as the reducing agent. The filler is incorporated into a polystyrene‐b‐polybutadiene‐b‐polystyrene (SBS) block copolymer matrix to form MMMs. As a result, both the permeability and selectivity of propylene/propane are improved after Cu(I) impregnation. The best performance is obtained for SBS/Cu@MIL‐101(Cr) MMM, and these values represent 17% and 54% improvements compared to those of SBS/MIL‐101(Cr) MMM, respectively. This result is attributed to the π‐complexation of the loaded Cu(I) by propylene gas, indicating that Cu@MIL‐101(Cr) with internal Cu(I) and a high pore volume acted as an effective filler to aid propylene/propane separation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46545.     

Poly(ether sulfone) supported hybrid poly(vinyl alcohol)–maleic acid–silicone dioxide membranes for the pervaporation separation of ethanol–water mixtures

Microporous poly(ether sulfone) (PES) supported hybrid polymer–inorganic membranes were prepared by the crosslinking of poly(vinyl alcohol) (PVA), maleic acid (MA), and SiO₂ via an aqueous sol–gel route and a solution‐casting method. The membrane performance was tested for the pervaporation separation of ethanol–water mixtures from 20 to 60 °C with a feed ethanol concentration of 96 wt %. The membrane characterization results reveal that different SiO₂ loadings affected the crystallinity and roughness of the membranes. The PVA–MA–SiO₂ membrane containing 10 wt % SiO₂ showed that SiO₂ nanoparticles were well dispersed within the polymer matrix; this resulted in significant enhancements in both the flux and selectivity. The membrane achieved a high water permeability of 1202 g·μm·m^?2 h^?1 kPa^?1 and a selectivity of 1027 for the separation of a 96 wt % ethanol‐containing aqueous solution. This enhanced membrane performance might have been due to the dense crosslinking membrane network, increased free volume, and uniform distribution of SiO₂ nanoparticles. Both the water and ethanol fluxes increased with the feed water concentration and temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44839.