Zeolite ZSM 5 membrane, whose permeance was up to 10 -6 mol/(m 2·s·Pa) and a magnitude higher than that of other groups, was prepared on α Al 2O 3 support by multi in situ hydrothermal treatments, using opt...Zeolite ZSM 5 membrane, whose permeance was up to 10 -6 mol/(m 2·s·Pa) and a magnitude higher than that of other groups, was prepared on α Al 2O 3 support by multi in situ hydrothermal treatments, using optimized sol prescription and cheap n butane as the structure directing agent. The membrane was characterized by means of XRD, SEM and single gas permeances measurements, which showed that it was dense and integral without large intercrystal pores and cracks. The permeance of H 2, N 2, C 3H 8 and n C 4H 10 was up to 2.35×10 -6 , 1.0×10 -6 , 1.13×10 -7 and 4.9×10 -8 mol/(m 2·s·Pa), respectively. Ideal selectivity of H 2/N 2, H 2/C 3H 8 and H 2/ n C 4H 10 was 2.45, 20.8 and 48, respectively. [WT5HZ]展开更多
High-permeance ZSM-5 zeolite membrane was prepared on porous tubular α-Al 2O 3 support by varying-temperature hydrothermal synthesis. XRD patterns show that the membrane consists of ZSM-5 zeolite crystals. SEM analys...High-permeance ZSM-5 zeolite membrane was prepared on porous tubular α-Al 2O 3 support by varying-temperature hydrothermal synthesis. XRD patterns show that the membrane consists of ZSM-5 zeolite crystals. SEM analysis indicates that few defects exist in the membrane and the thickness of the membrane is about 9 μm. The hydrogen permeance through the membrane is about 2.4×10 -6 mol/(m 2·s·Pa), and the separation factor for n-C 4H 10/i-C 4H 10 mixture (volume ratio 1∶1) is 40, which indicates that it has a high quality with high permeance and selectivity. Repeated nucleation and re-growth of the crystals on the support result in the dense membrane formation.展开更多
Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and ...Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53（S-MIL-53）and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.展开更多
Tailoring tire pore structure and surface chemistry of graphene-based laminates is essentially important for their applications as separation membranes. Usually, pure graphene oxide （GO） and completely reduced GO （...Tailoring tire pore structure and surface chemistry of graphene-based laminates is essentially important for their applications as separation membranes. Usually, pure graphene oxide （GO） and completely reduced GO （rGO） membranes suffer florn low water permeance because of the lack of pristine graphitic sp2 domains and very small interlayer spacing, respectively. In this work, we studied the influence of reduction degree on the structure and separation pertornrance of rGO membranes, tt was found that weak reduction retains the good dispersion and hydrophilicity of GO nanosheets. More importantly, it increases the number of pristine graphitic sp2 domains in rGO nanosheets while keeping the large interlayer spacing of the GO membranes in most regions at the same time. The resultant mernbranes show a high water permeance of 56.3 L m^-2 h^ -1 bar^ -1, which is about 4 times and over 10^4 times larger tban those of the GO and completely reduced rGO membranes, respectively, and high rejection over 95700 for various dyes. Furthermore, they show better structure stability and more superior separation perfor- mance than GO membranes in acid and alkali environments.展开更多
Thin film composite(TFC) membranes represent a highly promising platform for efficient nanofiltration(NF)processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein,highly...Thin film composite(TFC) membranes represent a highly promising platform for efficient nanofiltration(NF)processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein,highly permeable gradient phenolic membranes with tight selectivity are used as substrates to prepare TFC membranes with high permeances by the layer-by-layer assembly method. The negatively charged phenolic substrates are alternately assembled with polycation polyethylenimine(PEI) and polyanion poly(acrylic acid)(PAA)as a result of electrostatic interactions, forming thin and compact PEI/PAA layers tightly attached to the substrate surface. Benefiting from the high permeances and tight surface pores of the gradient nanoporous structures of the substrates, the produced PEI/PAA membranes exhibit a permeance up to 506 L? m-2?h-1?MPa-1, which is ~2–10 times higher than that of other membranes with similar rejections. The PEI/PAA membranes are capable of retaining N 96.1% of negatively charged dyes following the mechanism of electrostatic repulsion. We demonstrate that the membranes can also separate positively and neutrally charged dyes from water via other mechanisms.This work opens a new avenue for the design and preparation of high-flux NF membranes, which is also applicable to enhance the permeance of other TFC membranes.展开更多
Graphene oxide（GO） membranes play an important role in various nanofiltration applications including desalination, water purification, gas separation, and pervaporation. However, it is still very challenging to achi...Graphene oxide（GO） membranes play an important role in various nanofiltration applications including desalination, water purification, gas separation, and pervaporation. However, it is still very challenging to achieve both high separation efficiency and good water permeance at the same time. Here, we synthesized two kinds of GO-based composite membranes i.e. reduced GO（rGO）@MoO2 and rGO@WO3 by in-situ growth of metal nanoparticles on the surface of GO sheets. They show a high separation efficiency of ～100% for various organic dyes such as rhodamine B, methylene blue and evans blue, along with a water permeance over 125 Lm（-2） h（-1） bar（-1）. The high water permeance and rejection efficiency open up the possibility for the real applications of our GO composite membranes in water purification and wastewater treatment. Furthermore, this composite strategy can be readily extended to the fabrication of other ultrathin molecular sieving membranes for a wide range of molecular separation applications.展开更多
The permeation of various pure gas （H2, He, Ne, CH4 and At） through carbon membranes is investigated using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit pore is employed ins...The permeation of various pure gas （H2, He, Ne, CH4 and At） through carbon membranes is investigated using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit pore is employed instead of the one-dimensional pore. Compared with the experiments, simulation results show that the improvement of pore model is very necessary. The effects of membrane thickness, pore width and temperature on gas permeance and ideal separation factor are also discussed. Results show that gas permeates through membrane according to Knudsen diffusion in large pore, while Knudsen diffusion is accompanied by molecular sieving in small pore. Moreover, methane is easily adsorbed on the membrane surface due to strong attractive interactions of membrane and shows higher permeance than that of Knudsen flow. In addition, it is noted that when membrane thickness is thin enough the permeance of gas does not decrease with the increase of membrane thickness due to the strong adsorption until membrane resistance becomes dominant.展开更多
Reduced graphene oxide(RGO)membranes are theoretically more conducive to the rapid transport of water molecules in their channels compared with graphene oxide(GO)membranes,as they have fewer oxygen-containing function...Reduced graphene oxide(RGO)membranes are theoretically more conducive to the rapid transport of water molecules in their channels compared with graphene oxide(GO)membranes,as they have fewer oxygen-containing functional groups and more non-oxidized regions.However,the weak hydrophilicity of RGO membranes inhibits water entry into their channels,resulting in their low water permeability.In this work,we constructed wettable RGO-MXene channels by intercalating hydrophilic MXene nanosheets into the RGO membrane for improving the water permeance.The RGO-MXene composite membrane exhibits high pure water permeance of 62.1 L/(m^(2)·h·bar),approximately 16.8 times that of the RGO membrane(3.7 L/(m^(2)·h·bar)).Wettability test results and molecular dynamics simulations suggest that the improved water permeance results from the enhanced wettability of RGO-MXene membrane and increased rate of water molecules entering the RGOMXene channels.Benefiting from good conductivity,the RGO-MXene membrane with electroassistance exhibits significantly increased rejection rates for negatively charged dyes(from 56.0%at 0 V to 91.4%at 2.0 V for Orange G)without decreasing the permeate flux,which could be attributed to enhanced electrostatic repulsion under electro-assistance.展开更多
Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes ...Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube with a pore size of 2 μm in a gel system by varying-concentration synthesis with organic-free template. The first composition synthesis sol-gel was the same as seeds of molar composition and the second one was 12Na2O∶100SiO2∶2Al2O3∶5000H2O at 180 ℃ for 10 h, respectively. XRD shows that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicats that the zeolite films on the supports are defect free and the film thickness is approximately 8 μm. The permeances for H2, N2, CH4 and CO2 are 8.94×10-7, 3.27×10-7, 3.9×10-7, 3.14×10-7 and 0.874×10-7 mol·m2·s-1·Pa-1, respectively. The ideal selectivity of membrane at room temperature for H2/CO2, H2/N2, H2/CH4 are 2.84, 2.73 and 2.29, respectively.展开更多
文摘Zeolite ZSM 5 membrane, whose permeance was up to 10 -6 mol/(m 2·s·Pa) and a magnitude higher than that of other groups, was prepared on α Al 2O 3 support by multi in situ hydrothermal treatments, using optimized sol prescription and cheap n butane as the structure directing agent. The membrane was characterized by means of XRD, SEM and single gas permeances measurements, which showed that it was dense and integral without large intercrystal pores and cracks. The permeance of H 2, N 2, C 3H 8 and n C 4H 10 was up to 2.35×10 -6 , 1.0×10 -6 , 1.13×10 -7 and 4.9×10 -8 mol/(m 2·s·Pa), respectively. Ideal selectivity of H 2/N 2, H 2/C 3H 8 and H 2/ n C 4H 10 was 2.45, 20.8 and 48, respectively. [WT5HZ]
文摘High-permeance ZSM-5 zeolite membrane was prepared on porous tubular α-Al 2O 3 support by varying-temperature hydrothermal synthesis. XRD patterns show that the membrane consists of ZSM-5 zeolite crystals. SEM analysis indicates that few defects exist in the membrane and the thickness of the membrane is about 9 μm. The hydrogen permeance through the membrane is about 2.4×10 -6 mol/(m 2·s·Pa), and the separation factor for n-C 4H 10/i-C 4H 10 mixture (volume ratio 1∶1) is 40, which indicates that it has a high quality with high permeance and selectivity. Repeated nucleation and re-growth of the crystals on the support result in the dense membrane formation.
基金the financial support from the National Natural Science Foundation of China(No.21436009)
文摘Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53（S-MIL-53）and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.
基金supported by the National Key Research and Development Program of China(2016YFA0200101)the National Natural Science Foundation of China(51325205,51290273,and51521091)Chinese Academy of Sciences(KGZD-EW-303-1,KGZDEW-T06,174321KYSB20160011,and XDPB06)
文摘Tailoring tire pore structure and surface chemistry of graphene-based laminates is essentially important for their applications as separation membranes. Usually, pure graphene oxide （GO） and completely reduced GO （rGO） membranes suffer florn low water permeance because of the lack of pristine graphitic sp2 domains and very small interlayer spacing, respectively. In this work, we studied the influence of reduction degree on the structure and separation pertornrance of rGO membranes, tt was found that weak reduction retains the good dispersion and hydrophilicity of GO nanosheets. More importantly, it increases the number of pristine graphitic sp2 domains in rGO nanosheets while keeping the large interlayer spacing of the GO membranes in most regions at the same time. The resultant mernbranes show a high water permeance of 56.3 L m^-2 h^ -1 bar^ -1, which is about 4 times and over 10^4 times larger tban those of the GO and completely reduced rGO membranes, respectively, and high rejection over 95700 for various dyes. Furthermore, they show better structure stability and more superior separation perfor- mance than GO membranes in acid and alkali environments.
基金Supported by the National Basic Research Program of China(2015CB655301)the Natural Science Foundation of China(21825803)+2 种基金and the Natural Science Foundation of Jiangsu Province(BK20150063)the Program of Excellent Innovation Teams of Jiangsu Higher Education Institutionsthe Project of Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).
文摘Thin film composite(TFC) membranes represent a highly promising platform for efficient nanofiltration(NF)processes. However, the improvement in permeance is impeded by the substrates with low permeances. Herein,highly permeable gradient phenolic membranes with tight selectivity are used as substrates to prepare TFC membranes with high permeances by the layer-by-layer assembly method. The negatively charged phenolic substrates are alternately assembled with polycation polyethylenimine(PEI) and polyanion poly(acrylic acid)(PAA)as a result of electrostatic interactions, forming thin and compact PEI/PAA layers tightly attached to the substrate surface. Benefiting from the high permeances and tight surface pores of the gradient nanoporous structures of the substrates, the produced PEI/PAA membranes exhibit a permeance up to 506 L? m-2?h-1?MPa-1, which is ~2–10 times higher than that of other membranes with similar rejections. The PEI/PAA membranes are capable of retaining N 96.1% of negatively charged dyes following the mechanism of electrostatic repulsion. We demonstrate that the membranes can also separate positively and neutrally charged dyes from water via other mechanisms.This work opens a new avenue for the design and preparation of high-flux NF membranes, which is also applicable to enhance the permeance of other TFC membranes.
基金supported by the Ministry of Science and Technology of China (No. 2016YFA0200101)the National Natural Science Foundation of China (Nos. 51325205, 51290273, and 51521091)+1 种基金the Chinese Academy of Sciences (KGZD-EW-303-1, and KGZDEW-T06)the support of CAS-TWAS President Fellowship
文摘Graphene oxide（GO） membranes play an important role in various nanofiltration applications including desalination, water purification, gas separation, and pervaporation. However, it is still very challenging to achieve both high separation efficiency and good water permeance at the same time. Here, we synthesized two kinds of GO-based composite membranes i.e. reduced GO（rGO）@MoO2 and rGO@WO3 by in-situ growth of metal nanoparticles on the surface of GO sheets. They show a high separation efficiency of ～100% for various organic dyes such as rhodamine B, methylene blue and evans blue, along with a water permeance over 125 Lm（-2） h（-1） bar（-1）. The high water permeance and rejection efficiency open up the possibility for the real applications of our GO composite membranes in water purification and wastewater treatment. Furthermore, this composite strategy can be readily extended to the fabrication of other ultrathin molecular sieving membranes for a wide range of molecular separation applications.
基金Supported by the National Basic Research Program of China (No.2003CB615700), and National Natural Science Foundation ofChina (No.20376037).
文摘The permeation of various pure gas （H2, He, Ne, CH4 and At） through carbon membranes is investigated using a dual control volume grand canonical molecular dynamics method. A two-dimensional slit pore is employed instead of the one-dimensional pore. Compared with the experiments, simulation results show that the improvement of pore model is very necessary. The effects of membrane thickness, pore width and temperature on gas permeance and ideal separation factor are also discussed. Results show that gas permeates through membrane according to Knudsen diffusion in large pore, while Knudsen diffusion is accompanied by molecular sieving in small pore. Moreover, methane is easily adsorbed on the membrane surface due to strong attractive interactions of membrane and shows higher permeance than that of Knudsen flow. In addition, it is noted that when membrane thickness is thin enough the permeance of gas does not decrease with the increase of membrane thickness due to the strong adsorption until membrane resistance becomes dominant.
基金supported by the National Key Research and Development Program of China(No.2020YFA0211001)the National Natural Science Foundation of China(Nos.21976024 and 22106017)the Programme of Introducing Talents of Discipline to Universities(China)(B13012).
文摘Reduced graphene oxide(RGO)membranes are theoretically more conducive to the rapid transport of water molecules in their channels compared with graphene oxide(GO)membranes,as they have fewer oxygen-containing functional groups and more non-oxidized regions.However,the weak hydrophilicity of RGO membranes inhibits water entry into their channels,resulting in their low water permeability.In this work,we constructed wettable RGO-MXene channels by intercalating hydrophilic MXene nanosheets into the RGO membrane for improving the water permeance.The RGO-MXene composite membrane exhibits high pure water permeance of 62.1 L/(m^(2)·h·bar),approximately 16.8 times that of the RGO membrane(3.7 L/(m^(2)·h·bar)).Wettability test results and molecular dynamics simulations suggest that the improved water permeance results from the enhanced wettability of RGO-MXene membrane and increased rate of water molecules entering the RGOMXene channels.Benefiting from good conductivity,the RGO-MXene membrane with electroassistance exhibits significantly increased rejection rates for negatively charged dyes(from 56.0%at 0 V to 91.4%at 2.0 V for Orange G)without decreasing the permeate flux,which could be attributed to enhanced electrostatic repulsion under electro-assistance.
基金This work was financially supported by the Specialized Research Fund for the Doctoral Program of High Education (SRFDP)(No.B20020288015).
文摘Template-free nanosized ZSM-5 seeds with an average size of 15 nm were prepared from a synthesis solution with the composition 12Na2O∶100SiO2∶2Al2O3∶2500H2O. By the use of these seeds, thin ZSM-5 zeolite membranes were prepared on the outer surface of a porous α-alumina tube with a pore size of 2 μm in a gel system by varying-concentration synthesis with organic-free template. The first composition synthesis sol-gel was the same as seeds of molar composition and the second one was 12Na2O∶100SiO2∶2Al2O3∶5000H2O at 180 ℃ for 10 h, respectively. XRD shows that the film consists of well-crystallized ZSM-5 zeolite. SEM investigation indicats that the zeolite films on the supports are defect free and the film thickness is approximately 8 μm. The permeances for H2, N2, CH4 and CO2 are 8.94×10-7, 3.27×10-7, 3.9×10-7, 3.14×10-7 and 0.874×10-7 mol·m2·s-1·Pa-1, respectively. The ideal selectivity of membrane at room temperature for H2/CO2, H2/N2, H2/CH4 are 2.84, 2.73 and 2.29, respectively.
