Ceramic Supported PDMS and PEGDA Composite Membranes for CO2 Separation

Composite membranes have attracted increasing attentions owing to their potential applications for CO2 separation. In this work, ceramic supported polydimethylsiloxane （PDMS） and poly （ethylene glycol） diacrylate （PEGDA） composite membranes were prepared. The microstructure and physicochemical properties of the compos- ite membranes were characterized. Preparation conditions were systematically optimized. The gas separation performance of the as-prepared membranes was studied by pure gas and binary gas permeation measurement of CO〉 N2 and H〉 Experiments showed that PDMS, as silicone rubber, exhibited larger permeance and lower separation factors. Conversely, PEGDA composite membrane presented smaller gas permeance but higher ideal selectivity for CO2/N2. Compared to the performance of those membranes using polymeric supports or freestanding membranes, the two kinds of ceramic supported composite membranes exhibited higher gas permeance and acceptable selectivity. Therefore, the ceramic supported composite membrane can be expected as a candidate for CO2 separation from light gases.     

硅橡胶膜用于植物油/己烷胶团中溶剂回收的研究

Traditional solvent recovery in the extraction step of edible oil processing is distillation, which consumes large amounts of energy. If the distillation is replaced by membrane process, the energy consumption can be reduced greatly. In this work, two kinds of membrane, PDMS (polydimethylsiloxane) composite membrane and Zeolite filled PDMS membrane were prepared, in which asymmetric microporous PVDF (polyvinylidenefluoride) membrane prepared with phase inversion method was functioned as the microporous supporting layer in the flat-plate composite membrane. The different function compositions of the PDMS/PVDF com-posite membranes were characterized by reflection Fourier transform infrared (FTIR) spectroscopy. The surface and section of PDMS/PVDF composite membranes were investigated by scanning electron microscope (SEM). The PDMS NF (nanofiltration) membranes were then applied in the recovery of hexane from soybean oil/hexane miscellas (1︰3, mass ratio). The effects of pres-sure (0.5-1.5 MPa), cross-linking temperature and PDMS layer thickness on membrane performances were investigated. The results indicated that both two kinds of NF membranes were promising for solvent recovery, and zeolite filled in PDMS NF membrane could enhance the separation performance.     

Fouling-resistant Composite Membranes for Separation of Oil-in-water Microemulsions

Fouling-resistant ceramic-supported polymer composite membranes were developed for removal of oil-in-water （O/W） mieroemulsions. The composite membranes were featured with an asymmetric three-layer structure, i.e., a porous ceramic membrane substrate, a polyvinylidene fluoride （PVDF） ultrafiltration sub-layer, and a polyamide/polyvinyl alcohol （PVA） composite thin top-layer. The PVDF polymer was east onto the tubular porous ceramic membranes with an immersion precipitation method, and the polyamide/PVA composite thin top-layer was fabricated with an inteffaeial polymerization method. The effects of the sub-layer composition and the recipe in the inteffaeial polymerization for fabricating the top-layer on the structure and performance of composite membranes were systematically investigated. The prepared composite membranes showed a good performance for treating the O/W microemulsions with a mean diameter of about 2.41μm. At the operating pressure of 0.4MPa, the hydraulic permeability remained steadily about 190L·m^-2·h^-1, the oil concentration in the permeate was less than 1.6mg·L^-1, and the oil rejection coefficient was always higher than 98.5% throughout the operation from the beginning.     

Membrane materials in the pervaporation separation of aromatic/aliphatic hydrocarbon mixtures—A review

The separation of aromatic/aliphatic hydrocarbon mixtures is a significant process in chemical industry,but challenged in some cases.Compared with conventional separation technologies,pervaporation is quite promising in terms of its economical,energy-saving,and eco-ffiendly advantages.However,this technique has not been used in industry for separating aromatic/aliphatic mixtures yet.One of the main reasons is that the separation performance of existed pervaporation membranes is unsatisfactory.Membrane material is an important factor that affects the separation performance.This review provides an overview on the advances in studying membrane materials for the pervaporation separation of aromatic/aliphatic mixtures over the past decade.Explored pristine polymers and their hybrid materials (as hybrid membranes) are summarized to highlight their nature and separation performance.We anticipate that this review could provide some guidance in the development of new materials for the aromatic/aliphatic pervaporation separation.     

用于脱除C5及MTBE中甲醇的渗透汽化膜研究

Several pervaporation membranes, cellulose acetate (CA), polyvinylbutyral (PVB), poly(MMA-co-AA), MMA-AA-BA, CA/PVB blend and CA/poly(MMA-co-AA) blend, were prepared, and their pervaporation properties were evaluated by separation of methanol/C5 or methanol/MTBE (methyl tert-butyl ether). The results shows that the CA composite membrane has a high separation performance (flux Jmenthanol =350g.m-2.h-1 and separation factor a > 400) for methanol/C5 mixtures, and the pervaporation characteristics of MMA-AA-BA copolymer membranes changes with the ratio of copolymer. For CA/poly(MMA-co-AA) blend membrane, the pervaporation performance is improved in comparison with CA or poly(MMA-co-AA) membrane. From the experiment of CA/PVB blend membranes for methanol/MTBE mixture, it is found that the compatibility of blends may affect the separation features of blend membrane.     

ZSM-5填充PDMS复合膜渗透蒸发分离乙醛水溶液(英文)

Hydrophobic ZSM-5 zeolite filled polydimethylsiloxane(PDMS) composite membranes with Nylon micro-filtration membrane as the support layer were prepared to separate acetaldehyde from its aqueous solution.The composite membranes were characterized by Fourier transform infrared spectroscopy and X-ray diffraction.Their structural morphology and thermal stability were also examined.The swelling study showed that the composite membranes presented higher degree of swelling in aqueous solution of acetaldehyde than in pure water at 25 C,suggesting that the membranes have stronger sorption capacity in acetaldehyde solution.The effects of ZSM-5 filling content and acetaldehyde concentration on pervaporation performance of composite membranes were investigated.The permeation experiments at different temperatures showed that both selectivity and permeation flux of composite membranes increased with temperature.With 5%ZSM-5-PDMS/Nylon membrane at acetaldehyde mass concentration of 8% and 25℃,the separation factor of acetaldehyde/water achieved 35 and the permeation flux was 233.3 g·m-2·h-1.     

硅橡胶复合膜渗透汽化分离硫/汽油混合物

Worldwide environment has resulted in a limit on the sulfur content of gasoline. It is urgent to investigate the desulfurization of gasoline. The polydimethylsiloxane (PDMS)/polyetherimide (PEI) composite membranes were prepared by casting a PDMS solution onto porous PEI substrates and characterized by scanning electron microscope (SEM). The membranes were used for sulfur removal from gasoline by pervaporation. The effects of feed temperature, sulfur content in the feed and PDMS layer thickness on membrane performance were investigated, and an activation energy of permeation was obtained. Experimental results indicated that higher feed temperature yielded higher total flux and lower sulfur enrichment factor. The total flux varied little with the increase of sulfur content in the feed, but the sulfur enrichment factor first increased with the amount of thiophene added into the gasoline, and then the variation was little. The increase of PDMS layer thickness resulted in a smaller flux but a larger sulfur enrichment factor. The result indicates that the PDMS/PEI composite membranes are promising for desulfurization by pervaporation.     

表面偏析法制备用于乙醇渗透蒸发脱水的整体PVA-PES复合膜(英文)

A facile surface segregation method was utilized to fabricate poly(vinyl alcohol)-polyethersulfone (PVA-PES) composite membranes. PVA and PES were first dissolved in dimethyl sulfoxide (DMSO), then casted on a glass plate and immersed in a coagulation bath. During the phase inversion process in coagulation bath, PVA spontaneously segregated to the polymer solution/coagulation bath interface. The enriched PVA on the surface was further crosslinked by glutaraldehyde. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) confirmed the integral and asymmetric membrane structure with a dense PVA-enriched surface and a porous PES-enriched support, as well as the surface enrichment of PVA. The coverage fraction of the membrane surface by PVA reached up to 86.8% when the PVA content in the membrane recipe was 16.7% (by mass). The water contact angle decreased with the increase of PVA content. The effect of co-agulation bath type on membrane structure was analyzed. The membrane pervaporation performance was evaluated by varying the PVA content, the annealing temperature, feed concentration and operation temperature. The mem-brane exhibited a fairly good ethanol dehydration capacity and long-term operational stability.     

Recent developments on catalytic membrane for gas cleaning

Catalytic membrane, a novel membrane separation technology that combines catalysis and separation, exhibits significant potential in gas purification such as formaldehyde, toluene and nitrogen oxides(NO_x). The catalytic membrane can remove solid particles through membrane separation and degrade gaseous pollutants to clean gas via a catalytic reaction to achieve green emissions. In this review, we discussed the recent developments of catalytic membranes from two aspects: preparation of catalytic membrane and its application in gas cleaning.Catalytic membranes are divided into organic catalytic membranes and inorganic catalytic membranes depending on the substrate materials. The organic catalytic membranes which are used for low temperature operation(less than 300 °C) are prepared by modifying the polymers or doping catalytic components into the polymers through coating, grafting, or in situ growth of catalysts on polymeric membrane. Inorganic catalytic membranes are used at higher temperature(higher than 500 °C). The catalyst and inorganic membrane can be integrated through conventional deposition methods, such as chemical(physical) vapor deposition and wet chemical deposition. The application progress of catalytic membrane is focused on purifying indoor air and industrial exhaust to remove formaldehyde, toluene, NO_x and PM2.5, which are also summarized. Perspectives on the future developments of the catalytic membranes are provided in terms of material manufacturing and process optimization.     

Fabrication of graphene oxide composite membranes and their application for pervaporation dehydration of butanol

As a new kind of 2D nanomaterials, graphene oxide (GO) with 2–4 layers was fabricated via a modified Hummers method and used for the preparation of pervaporation (PV) membranes. Such GO membranes were prepared via a facile vacuum-assisted method on anodic aluminium oxide disks and applied for the dehydration of butanol. To obtain GO membranes with high performance, effects of pre-treatments, including high-speed centrifugal treat-ment of GO dispersion and thermal treatment of GO membranes, were investigated. In addition, effects of oper-ation conditions on the performance of GO membranes in the PV process and the stability of GO membranes were also studied. It is of benefit to improve the selectivity of GO membrane by pre-treatment that centrifuges the GO dispersion with 10000 r·min?1 for 40 min, which could purify the GO dispersion by removing the large size GO sheets. As prepared GO membrane showed high separation performance for the butanol/water system. The separation factor was 230, and the permeability was as high as 3.1 kg·m?2·h?1 when the PV temperature was 50 °C and the water content in feed was 10%(by mass). Meanwhile, the membrane still showed good stabil-ity for the dehydration of butanol after running for 1800 min in the PV process. GO membranes are suitable candidates for butanol dehydration via PV process.     

Pervaporation properties of polyvinyl alcohol/ceramic composite membrane for separation of ethyl acetate/ethanol/water ternary mixtures

In further purification of ethyl acetate (EAC) process, azeotropic distillation or extractive distillation is usually applied. High energy consumption limits the economic profit of the process. In this study, pervaporation separation of EAC/ethanol (EA)/water ternary mixtures using the ceramic-supported polyvinyl alcohol (PVA) composite membrane was investigated to substitute the azeotropic distillation or extractive distillation. Swelling experiments were performed to evaluate the sorption characteristic of the membrane. Flory-Huggins theory was applied to study the interaction between the membrane and the penetrant. The UNIFAC model was adopted to investigate the variation of the penetrant activity in the membrane. The effects of operation temperature, feed water content and feed flow rate on the PV performance of the membrane were systematically investigated. The composite membrane exhibited high PV performance with the total flux of 2.1 kg·m⁻²·h⁻¹ and 94.9 wt% permeate concentration of water (operation condition: feed composition 82.6 wt% EAC, 8.4 wt% EA, 9 wt% water, feed temperature 60 °C, feed flow rate 252 mL· min⁻¹). The PV performance of the membrane varied slightly over a continuous PV experiment period of 110 h. Our results demonstrated that the PVA/ceramic membrane was a potential candidate for the purification of EAC/EA/water ternary mixtures.     

PDMS/ZIF-8 coating polymeric hollow fiber substrate for alcohol permselective pervaporation membranes

In order to develop high performance composite membranes for alcohol permselective pervaporation (PV), poly (dimethylsiloxane)/ZIF-8 (PDMS/ZIF-8) coated polymeric hollow fiber membranes were studied in this research. First, PDMS was used for the active layer, and Torlon®, PVDF, Ultem®, and Matrimid® with different porosity were used as support layer for fabrication of hollow fiber composite membranes. The performance of the membranes varied with different hollow fiber substrates was investigated. Pure gas permeance of the hollow fiber was tested to investigate the pore size of all fibers. The effect of support layer on the mass transfer in hydrophobic PV composite membrane was investigated. The results show that proper porosity and pore diameter of the support are demanded to minimize the Knudsen effect. Based on the result, ZIF-8 was introduced to prepare more selective separation layer, in order to improve the PV performance. The PDMS/ZIF-8/Torlon® membrane had a separation factor of 8.9 and a total flux of 847 g·m^-2·h^-1. This hollow fiber PDMS/ZIF-8/Torlon® composite membrane has a great potential in the industrial application.     

Tubular composite PVA ceramic supported membrane for bio-ethanol production

Thin polyvinyl alcohol (PVA) layers loaded with fumed silica were coated on porous ceramic supports. Scanning electron microscope (SEM) was used to characterize the ceramic-supported thin PVA active layers and the effects of coating gel PVA concentration on thickness and density of the active layers were investigated. Pervaporation (PV) dehydration of 90 wt.% ethanol was performed at temperatures of 30, 45 and 60 °C. The values of water flux (0.05–2.92 kg/m² h) and selectivity (3–180) exceed typical values obtained for pure PVA membranes. Besides the pervaporation separation index (PSI) varies from 5.84 to 82.81. Compared to pure PVA membrane with maximum PSI of 47.2, the pervaporation performance was significantly improved. The best separation performance was obtained using the membrane prepared from 5 wt.% PVA solution containing 6 wt.% fumed silica and at pervaporation temperature of 45 °C with permeation flux of 1.69 kg/m² h, and selectivity of 50. The highest permeation flux, selectivity and PSI was 2.92 kg/m² h, 180 and 82.81, obtained at 60, 30 and 45 °C, respectively, while using membranes loaded with 8, zero and 6 wt.% of fumed silica in PVA membrane prepared from 5, 10 and 5 wt.% PVA solutions, respectively. The novel ceramic support increased mechanical strength of the membrane and protected the ultrathin polymeric top active layer under aggressive operating conditions, especially high pressure gradient across the membrane. Incorporation of fumed silica also resulted in higher water permeation flux. Due to these results, the synthesized membranes are suitable for ethanol purification in industrial scales.     

Simultaneously enhancing interfacial adhesion and pervaporation separation performance of PDMS/ceramic composite membrane via a facile substrate surface grafting approach

A facile substrate surface silane-grafting approach was demonstrated to enhance both interfacial adhesion and pervaporation separation performance of PDMS composite membrane. With C₁₆ grafted ceramic substrate, the PDMS/ceramic composite membrane exhibited up to 1.7 times stronger interfacial adhesion force between separation layer and substrate layer, meanwhile 1.5 times larger butanol/water separation factor that is higher than state-of-the-art membranes. This novel approach paves a new avenue to developing composite membranes with high and stable separation performance.     

影响渗透汽化中空纤维复合膜分离性能的制备工艺研究

采用聚乙烯醇（ＰＶＡ）为分离层的模材料,以浸涂工艺把ＰＶＡ复合到聚砜（ＰＳ）或聚丙烯腈（ＰＡＮ）的中空纤维支撑层上,在长度为０．４ｍ的不锈钢管中组装若干根中空纤维复合膜测定对乙醇水溶液的渗透汽化（ＰＶ）分离性能。结果表明,ＰＶＡ／ＰＡＮ中空纤维复合膜的性能优于ＰＶＡ／ＰＳ,内径较大（１．３ｍｍ）的优于内径上（０．４ｍｍ）者,ＰＶＡ水溶液在中空纤维支撑层上的涂复次数对复合膜ＰＶ分离性能、以及ＰＶＡ／     

Preparation of PFSA‐PVA/PSf hollow fiber membrane for IPA/H2O pervaporation process

Using Na⁺ form of perfluorosulfonic acid (PFSA) and poly(vinyl alcohol) (PVA) as coating materials, polysulfone (PSf) hollow fiber ultrafiltration membrane as a substrate membrane, PFSA‐PVA/PSf hollow fiber composite membrane was fabricated by dip‐coating method. The membranes were post‐treated by two methods of heat treatment and by both heat treatment and chemical crosslinking. Maleic anhydride (MAC) aqueous solution was used as chemical crosslinking agent using 0.5 wt % H₂SO₄ as a catalyst. PFSA‐PVA/PSf hollow fiber composite membranes were used for the pervaporation (PV) separation of isopropanol (IPA)/H₂O mixture. Based on the experimental results, PFSA‐PVA/PSf hollow fiber composite membrane is suitable for the PV dehydration of IPA/H₂O solution. With the increment of heat treatment temperature, the separation factor increased and the total permeation flux decreased. The addition of PVA in PFSA‐PVA coating solution was favorable for the improvement of the separation factor of the composite membranes post‐treated by heat treatment. Compared with the membranes by heat treatment, the separation factors of the composite membranes post‐treated by both heat treatment and chemical crosslinking were evidently improved and reached to be about 520 for 95/5 IPA/water. The membranes post‐treated by heat had some cracks which disappeared after chemical crosslinking for a proper time. Effects of feed temperature on PV performance had some differences for the membranes with different composition of coating layer. The composite membranes with the higher mass fraction of PVA in PFSA‐PVA coating solution were more sensitive to temperature. It was concluded that the proper preparation conditions for the composite membranes were as follows: firstly, heated at 160°C for 1 h, then chemical crosslinking at 40°C for 3 h in 4% MAC aqueous solution. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

模拟的发酵液组分对聚二甲基硅氧烷/陶瓷复合膜渗透汽化性能的影响

对所制备的聚二甲基硅氧烷（PDMS）/陶瓷复合膜进行了渗透汽化性能表征。通过在乙醇-水混合体系中添加不同的模拟发酵液组分;如葡萄糖（多羟基醛）、甘油（多元醇）、丁二酸（有机酸）、KCl（无机盐）;考察了各组分对复合膜渗透汽化性能的影响。研究发现：在333 K下;在乙醇浓度为65 g·L-1的混合物中添加不同浓度的第三组分;有机添加物对膜的渗透汽化性能没有明显影响;而无机盐的加入使膜的分离因子稍有提高。所制备的PDMS/陶瓷复合膜;在上述渗透汽化过程中表现出良好的稳定性和对乙醇的优先选择性;渗透通量和分离因子（醇/水）分别在4.5～4.7 kg·m^-2·h^-1、8.3～10.3之间。     

无机盐对聚二甲基硅氧烷/陶瓷复合膜渗透汽化性能的影响

将渗透汽化应用于醇/水体系的分离,具有诸多显著的优势。然而,目前的研究大都基于二元体系,而实际的应用体系是多元的,还包含少量无机盐和糖类等,它们的存在对膜的性能具有一定的影响。本文研究了NaCl、KCl和MgCl2 3种无机盐的加入对聚二甲基硅氧烷 （PDMS）/陶瓷复合膜渗透汽化性能的影响。结果表明,在313 K,无机盐的加入使复合膜的分离因子和通量均有所提高。其中二价盐MgCl2对渗透汽化性能的影响最为显著,分离因子最大提高到醇/水体系的2.8倍。而一价盐NaCl和KCl的加入,使分离因子分别提高为醇/水体系的2.5倍和2.4倍。同时借助于Setschenow扩展方程计算了乙醇活度,对实验结果进行了初步的解释。     

Characterization of sodium alginate and poly(vinyl alcohol) blend membranes in pervaporation separation

By blending a rigid polymer, sodium alginate (SA), and a flexible polymer, poly(vinyl alcohol) (PVA), SA/PVA blend membranes were prepared for the pervaporation separation of ethanol–water mixtures. The rigid SA membrane showed a serious decline in flux and a increase in separation factor due to the relaxation of polymeric chains, whereas the flexible PVA membrane kept consistent membrane performance during pervaporation. Compared with the nascent SA membrane, all of the blend membranes prepared could have an enhanced membrane mobility by which the relaxation during pervaporation operation could be reduced. From the pervaporation separation of the ethanol–water mixtures along with the temperature range of 50–80°C, the effects of operating temperature and PVA content in membrane were investigated on membrane performance, as well as the extent of the relaxation. The morphology of the blend membrane was observed with PVA content by a scanning electron microscopy. The relaxational phenomena during pervaporation were also elucidated through an analysis on experimental data of membrane performance measured by repeating the operation in the given temperature range. SA/PVA blend membrane with 10 wt % of PVA content was crosslinked with glutaraldehyde to enhance membrane stability in water, and the result of pervaporation separation of an ethanol–water mixture through the membrane was discussed. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:949–959, 1998