F127对热致相分离法制备的亲水性PVB/F127共混中空纤维膜性能的影响(英文)

Hydrophilic poly(vinyl butyral) (PVB)/Pluronic F127 (F127) blend hollow fiber membranes were prepared via thermally induced phase separation (TIPS), and the effects of blend composition on the performance of hydrophilic PVB/F127 blend hollow fiber membrane were investigated. The addition of F127 to PVB/polyethylene glycol (PEG) system decreases the cloud point temperature, while the cloud point temperature increases slightly with the addition of F127 to 20% (by mass) PVB/F127/PEG200 system when the concentration of F127 is not higher than 5% (by mass). Light scattering results show that the initial inter-phase periodic distance formed from the phase separation of 20% (by mass) PVB/F127/PEG200 system decreases with the addition of F127, so does the growth rate during cooling process. The blend hollow fiber membrane prepared at air-gap 5mm, of which the water permeability increases and the rejection changes little with the increase of F127 concentration. For the membrane prepared at zero air-gap, both water permeability and rejection of the PVB/F127 blend membrane are greater than those of PVB membrane, while the tensile strength changes little. Elementary analysis shows that most F127 in the polymer solution can firmly exist in the polymer matrix, increasing the hydrophilicity of the blend membrane prepared at air-gap of 5mm.     

热致相分离法iPP中空纤维微空膜结构与性能--稀释剂的作用

Isotactic polypropylene （iPP） hollow fiber microporous membranes were prepared using thermally induced phase separation （TIPS） method. Di-n-butyl phthalate （DBP）, dioctyl phthalate （DOP）, and the mixed solvent were used as diluents. The effect of α （DOP mass fraction in diluent） on the morphology and performance of the hollow fiber was investigated. With increasing α, the morphology of the resulting hollow fiber changes from typical cellular structure to mixed structure, and then to typical particulate structure. As a result, the permeability of the hollow fiber increases sharply, and the mechanical properties of the hollow fiber decrease obviously. It is suggested that the morphology and performances of iPP hollow fiber microporous membrane can be controlled via adjusting the compatibility between iPP and diluent.     

Fabrication and characterization of novel foaming polyurethane hollow fiber membrane

Foam-like materials had attracted great interest as promising absorbent. In this study, thermoplastic polyurethane(TPU) block sponge was synthesized. Polyester(PET) braid tubular reinforced polyurethane(PU) spongy hollow fiber membrane was prepared by a concentric circular spinning method. The method was woven from an outer coated water-blown PU separation layer and inner PET braid tubular. We have developed a simple and useful preparation technique for the PU spongy hollow fiber membrane. For the first time, the PU spongy hollow fiber membrane was prepared using a coating and controlled foaming technique. The influence of toluene isocyanate index on the physical properties, morphology, and structure of flexible PU sponge was discussed in terms of water contact angle(CA), pure water flux(PWF), Fourier Transform Infrared Analysis(FTIR),pressure-responsive property, and pull-out strength. The morphologies of the membranes were investigated by scanning electron microscopy. We have characterized the foams from an intuitive point of view and demonstrated that the dimensional morphology of the membrane was closely related to isocyanate index. The result showed that the surface cell size of the PU sponge hollow fiber membrane gradually decreased with an increase of the isocyanate index. Due to the elasticity of PU at room temperature, the pressure responsive characteristic of the membrane was prepared. When isocyanate index was 1.05, the interface bonding strength of PU spongy hollow fiber membranes reached as high as 0.37 MPa, porosity and PWF were 71.5% and 415.5 L·m~(-2)·h~(-1),respectively.     

Scale-up of NaA zeolite membranes onα-Al2O3 hollow fibers by a secondary growth method with vacuum seeding

NaA zeolite membranes were prepared by secondary growth method on the outer surface ofα-Al2O3 hollow fiber supports. Vacuum seeding method was used for planting zeolite seeds on the support surfaces. Hydrother-mal crystallization was then carried out in a synthesis solution with molar ratio of Al2O3:SiO2:Na2O:H2O=1:2:2:120 at 100 °C for 4 h. Effects of seeding conditions on preparation of hollow fiber NaA zeolite membranes were extensively investigated. Moreover, hollow fiber membrane modules with packing membrane areas of ca. 0.1 and 0.2 m2 were fabricated to separate ethanol/water mixture. It is found that the thickness of seed layer is obviously affected by seed suspension concentration, coating time and vacuum degree. Close-packing seed layer is required to obtain high-quality membranes. The optimized seeding conditions (seed suspension mass concentration of 0.5%–0.7%, coating time of 5 s and vacuum degree of 10 kPa) lead to dense NaA zeolite layer with a thickness of 6–8μm. Typically, an as-synthesized hollow fiber NaA zeolite membrane exhibits good pervaporation performance with a permeation flux of 7.02 kg·m?2·h?1 and separation factor N 10000 for sepa-ration of 90%(by mass) ethanol/water mixture at 75 °C. High reproducibility has been achieved for batch-scale production of hollow fiber NaA zeolite membranes by the hydrothermal synthesis approach.     

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.     

平板式超声对污染聚偏氟乙烯中空纤维超滤膜清洗

Polyvinylidenefluoride （PVDF） hollow fiber ultrafiltration membrane is frequently employed in water treatment. However, the fouling of ultrafiltration membranes affects the economic effectiveness of such process significantly. The ultrasound generated by flat plate transducer （UFPT） was used to clean the polluted PVDF ultrafiltration membrane with 2 g·L^-1 of citric acid aqueous solution in our study. The effects of UFPT intensity on the membrane surface were studied. The new membrane was easy to be polluted by the saturated CaCl2 solution. A synergistic effect of UFPT and 2 g·L^-1 citric acid aqueous solution could remove the foul of the membrane, and its flux could be recovered about 81%. The flux recovery of old membrane polluted was increased to 73.2% after 7 h soaking in citric acid aqueous solution, but its flux recovery without soaking was only increased to 56.2%.     

Absorption of Low Concentration Sulfur Dioxide Using Liquid-containing Microporous Membrane

The absorption of low concentration SO2 in flue gas by using the module of liquid-containing microporous membrane which is made up of hollow fiber and citric acid-sodium citrate buffer solution was investigated. The absorption efficiency of hydrophilic and hydrophobic membranes by using the concept of dynamic contact angle was mainly studied. The influences on absorption efficiency from absorption time, flowrate of gas phase, SO2 concentration of gas phase, air pressure, citrate concentration, pH value of solution as well as the generation of sulfate radical in absorption solution were examined. The results indicate that the hydrophobic hollow fiber membrane is better than hydrophilic membrane, the absorption efficiency decreases with increasing absorption time, gas phase flowrate, gas phase SO2 concentration and air pressure, the absorption rate and capacity of SO2 can be improved by increasing the citrate concentration, the absorption efficiency can be improved by increasing the pH value of citrate solution, the concentration of SO42- in absorption solution increases linearly with the absorption time at a rate around 0.192 g/(L×h).     

MASS TRANSFER IN MEMBRANE ABSORPTIONDESORPTION OF AMMONIA FROM AMMONIA WATER

Hydrophobic membrane can provide fast mass transfer for absorption-desorption of gasesform liquid to absorbent.The removal of ammonia from ammonia water and absorption with dilutesulphuric acid was studied in a pilot plant with polypropylene hollow fiber column,The removalrate and influences of operation temperature,flow rate and concentration on mass transferperformances were discussed mathematically.Experimental results and computer calculation show thatthe ammonia removal rate is not affected by the feed concentration for a given system.Both partialand overall mass transfer coefficients vary along the axis of the fiber,and the mass transfer for themembrane process is controlled by membrane resistance.     

Thermal conductivity of PVDF/PANI-nanofiber composite membrane aligned in an electric field

Poly(vinylidene fluoride)(PVDF) is a semi-crystalline thermoplastic polymer with excellent thermal stability,electrochemical stability and corrosion resistance, which has been widely studied and applied in industrial nonmetallic heat exchanger and piezoelectric-film sensor. In this study, polyaniline(PANI) nanofibers were synthesized using dodecylbenzene sulfonic acid as the surfactant. The obtained PANI nanofibers were blended in PVDF matrix to enhance thermal conductivity and tensile strength of composite materials. Electric field was applied for the orientation of membrane structure during membrane formation. Scanning electron microscope(SEM) images exhibited that the PANI nanofibers were well-dispersed in the composite membranes. The structure of composite membranes was more orderly after alignment. X-ray diffraction(XRD) and differential scanning calorimetry(DSC) indicated that the content of PANI nanofibers contributed to the transformation of PVDF from α-phase to β-phase. Both the tensile strength and thermal conductivity of composite membranes were significantly improved. This tendency was further enhanced by the application of electric field. The maximum tensile strength was obtained when the content of PANI nanofibers was 3 wt%, which was 46.44% higher than that of pure PVDF membrane. The maximum thermal conductivity of composite membranes after alignment was 84.5% greater than that of pure PVDF membrane when the content of PANI nanofibers was 50 wt%. The composite membrane is a promising new potential material in heat transfer field and the mechanism explored in this study would be informative for further development of similar thermal conductive polymeric materials.     

引入天然黏合剂作为黏合层的复合膜用于渗透蒸发乙醇脱水(英文)

A high performance composite membrane was prepared under the inspiration of bioadhesion principles for pervaporative dehydration of ethanol. Chitosan (CS) and polyacrylonitrile (PAN) ultrafiltration membranes were used as the active layer and the support layer, respectively. Guar gum (GG), a natural bioadhesive, was in-troduced as the intermediate bonding layer to improve the separation performance and stability of the fabricated CS/GG/PAN composite membranes. The contact angle of the GG layer was just between those of the CS layer and the PAN layer, minimizing the difference of hydrophilicity between the active layer and the support layer. The peeling strength of the composite membrane was significantly enhanced after the introduction of the GG layer. The effects of preparation conditions and operation conditions including GG concentration, operating tempera-ture and ethanol concentration in feed on the pervaporation performance were investigated. The as-fabricated CS/GG/PAN composite membrane showed the optimum performance with a permeation flux of up to 804 g·m?2·h?1 and a separation factor higher than 1900. Besides, the composite membranes exhibited a desir-able long-term operational stability.     

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.     

Preparation of hydrophobic flat sheet membranes from PVDF-HFP copolymer for enhancing the oxygen permeance in nitrogen/oxygen gas mixture

In this study, poly(vinilydene fluoride-co-hexafluoropropylene)(PVDF-HFP) was used for preparation of hydrophobic membranes using non-solvent induced phase inversion(NIPS) technique. PVDF-HFP copolymer with concentrations of 10 wt% and 12 wt% was prepared to investigate the effect of polymer concentration on pore structure,morphology, hydrophobicity and performance of prepared membranes. Besides, the use of two coagulation baths with the effects of parameters such as coagulant time, polymer type and concentration, and the amount of nonsolvent were studied. The performance of prepared membranes was evaluated based on the permeability and selectivity of oxygen and nitrogen from a gas mixture of nitrogen/oxygen under operating conditions of feed flow rate(1–5 L·min~(-1)), inlet pressure to membrane module(0.1–0.5 MPa) and temperatures between 25 and 45 °C. The results showed that the use of two coagulation baths with different compositions of distillated water and isopropanol,coagulant time, polymer type and concentration, and the amount of non-solvent additive have the most effect on pore structure, morphology, thickness, roughness and crystallinity of fabricated membranes. Porosity ranges for the three fabricated membranes were determined, where the maximum porosity was 73.889% and the minimum value was 56.837%. Also, the maximum and minimum average thicknesses of membrane were 320.85 μm and115 μm. Besides, the values of 4.7504 × 10~(-7) mol· m~(-2)· s~(-1)· Pa~(-1), 0.525 and 902.126 nm were achieved for maximum oxygen permeance, O_2/N_2 selectivity and roughness, respectively.     

Preparation of dual‐layer acetylated methyl cellulose hollow fiber membranes via co‐extrusion using thermally induced phase separation and non‐solvent induced phase separation methods

Dual‐layer acetylated methyl cellulose (AMC) hollow fiber membranes were prepared by coupling the thermally induced phase separation (TIPS) and non‐solvent induced phase separation (NIPS) methods through a co‐extrusion process. The TIPS layer was optimized by investigating the effects of coagulant composition on morphology and tensile strength. The solvent in the aqueous coagulation bath caused both delayed liquid–liquid demixing and decreased polymer concentration at the membrane surface, leading to porous structure. The addition of an additive (triethylene glycol, (TEG)) to the NIPS solution resolved the adhesion instability problem of the TIPS and NIPS layers, which occurred due to the different phase separation rates. The dual‐layer AMC membrane showed good mechanical strength and performance. Comparison of the fouling resistance of the AMC membranes with dual‐layer polyvinylidene fluoride (PVDF) hollow fiber membranes fabricated with the same method revealed less fouling of the AMC than the PVDF hollow fiber membrane. This study demonstrated that a dual‐layer AMC membrane with good mechanical strength, performance, and fouling resistance can be successfully fabricated by a one‐step process of TIPS and NIPS. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42715.     

Towards superior permeability and antifouling performance of sulfonated polyethersulfone ultrafiltration membranes modified with sulfopropyl methacrylate functionalized SBA-15

A non-solvent induced phase separation (NIPS) process was used to fabricate a series of sulfonated polyethersulfone (SPES) membranes blending with different concentrations of SBA-15-g-PSPA with the applications in the ultrafiltration (UF) process. SBA-15 was modified with 3-methacrylate-propyltrimethoxysilane (MPS) to form SBA-15-g-MPS. It was further modified with the charge tailorable polymer chains by reacting with 3-sulfopropyl methacrylate potassium salt. The nanoparticles were uniformly dispersed and finger-like channels were developed within the membrane. The adding of surface modified SBA-15-g-PSPA nanoparticles has significantly improved membrane water permeability, hydrophilicity, and antifouling properties. The pure water fluxes of the composite SPES membranes were significantly higher than the pristine SPES membrane. For the membrane containing 5% (mass) of SBA-15-g-PSPA (MSSPA5), the pure water flux was increased dramatically to 402.15 L·m^-2·h^-1, which is ~1.5 times that of MSSPA0 (268.0 L·m^-2·h^-1). The high flux rate was achieved with 3% (mass) of SBA-15 nanoparticles with retained high rejection ratio 98% for natural organic matter. The results indicate that the fashioned composite membrane comprising SBA-15-g-PSPA nanoparticles have a promising future in ultrafiltration applications.     

Fabrication and characterization of hydrophobic PVDF hollow fiber membranes for desalination through direct contact membrane distillation

The mixture of inorganic salt LiCl and soluble polymer polyethylene glycol (PEG) 1500 as non-solvent additive was introduced to fabricate hydrophobic hollow fiber membrane of polyvinylidene fluoride (PVDF) by phase inversion process, using N,N-dimethylacetamide (DMAc) as solvent and tap water as the coagulation medium. Compared with other three membranes from PVDF/DMAc, PVDF/DMAc/LiCl and PVDF/DMAc/PEG 1500 dope solution, it can be observed obviously by scanning electron microscope (SEM) that the membrane spun from PVDF/DMAc/LiCl/PEG 1500 dope had longer finger-like cavities, ultra-thin skins, narrow pore size distribution and porous network sponge-like structure owing to the synergistic effect of LiCl and PEG 1500. Besides, the membrane also exhibited high porosity and good hydrophobicity. During the desalination process of 3.5 wt% sodium chloride solution through direct contact membrane distillation (DCMD), the permeate flux achieved 40.5 kg/m² h and the rejection of NaCl maintained 99.99% with the feed solution at 81.8 °C and the cold distillate water at 20.0 °C, this performance is comparable or even higher than most of the previous reports. Furthermore, a 200 h continuously desalination experiment showed that the membrane had stable permeate flux and solute rejection, indicating that the as-spun PVDF hollow fiber membrane may be of great potential to be utilized in the DCMD process.     

Plant-inspired biomimetic hybrid PVDF membrane co-deposited by tea polyphenols and 3-amino-propyl-triethoxysilane for high-efficiency oil-in-water emulsion separation

Membrane pollution caused by separating oily wastewater is a big challenge for membrane separation technology. Recently, plant-/mussel-inspired interface chemistry has received more and more attention. Herein, a high antifouling poly (vinylidene fluoride) (PVDF) membrane, coated with tea polyphenols (TP, extracted from green tea) and 3-amino-propyl-triethoxysilane (APTES), was developed to purify oil-in-water emulsions. ATR-FTIR, XPS and SEM were used to demonstrate the evolution of surface biomimetic hybrid coatings. The performances of the developed membranes were investigated by pure water permeability and oil rejection for various surfactant-stabilized oil-in-water emulsions. The experimental results revealed that the membrane deposited with a mass ratio of 0.1/0.2 exhibited ultrahigh pure water permeability (14570 L·m^-2·h^-1·bar^-1, 1 bar=0.1 MPa) and isooctane-in-water emulsion permeability (5391 L·m^-2·h^-1·bar^-1) with high separation efficiency (>98.9%). Even treated in harsh environment (acidic, alkaline and saline) for seven days, the membrane still maintained considerable underwater oleophobic property (148°–153°). The fabricated plant-inspired biomimetic hybrid membranes with excellent performances light a broad application prospect in the field of oily wastewater treatment.     

Fabrication of poly(vinylidene fluoride) membrane via thermally induced phase separation using ionic liquid as green diluent

Ionic liquid(IL), 1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF6) as a new and environmentally friendly diluent was introduced to prepare poly(vinylidene fluoride)(PVDF) membranes via thermally induced phase separation(TIPS). Phase diagram of PVDF/[BMIM]PF6 was measured. The effects of polymer concentration and quenching temperature on the morphologies, properties, and performances of the PVDF membranes were investigated. When the polymer concentration was 15 wt%, the pure water flux of the fabricated membrane was up to nearly 2000 L·m~(-2)·h~(-1), along with adequate mechanical strength. With the increasing of PVDF concentration and quenching temperature, mean pore size and water permeability of the membrane decreased. SEM results showed that PVDF membranes manufactured by ionic liquid(BMIm PF6) presented spherulite structure. And the PVDF membranes were represented as β phase by XRD and FTIR characterization. It provides a new way to prepare PVDF membranes with piezoelectric properties.     

A design of composite hollow fiber membranes with tunable performance and reinforced mechanical strength

A new design of hollow fiber membranes with high mechanical strength, great surface area per volume ratio and tunable filtration performance is presented. This newly developed hollow fiber membrane was produced by an intensified production process, in which the processes of thermally induced phase separation (TIPS), non‐solvent induced phase separation (NIPS), and interfacial polymerization (IP) were combined. PVDF (polyvinylidene difluoride) hollow fiber membranes (produced by TIPS) were used as support substrates. Afterwards, PES (polyethersulfone) (made by NIPS) and PA (polyamide) layers (manufactured by IP) were coated one by one. The pure water permeability, molecular weight cut off (MWCO), salt rejection, tensile stress together with surface and cross‐sectional morphology indicate that the properties of the hollow fiber membranes can be easily adjusted from microfiltration‐like to nanofiltration‐like membranes only by varying the presence of the IP step and the concentration in the PES layer in the production system. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41247.     

聚砜/聚苯胺-嵌段式聚醚Pluronic F127复合超滤膜的制备及性能

选用具有不同改性机理的嵌段式聚醚Pluronic F127与聚苯胺(PANI)纳米纤维共同作为添加剂共混改性聚砜(PSf)超滤膜,利用浸没沉淀相转化法制备出PSf/PANI-F127复合超滤膜。考察、比较并分析两种改性材料同时存在对膜结构和膜性能的影响。膜结构通过傅里叶衰减全反射红外(ATR-FTIR)、X射线光电子能谱(XPS)、X射线能量色散谱(EDS)、扫描电镜(SEM)和接触角等测试表征。膜性能通过纯水通量、截留率、抗污染性能以及添加剂稳定性结果进行评价。实验结果表明,Pluronic F127的加入可以更有效地提高膜表面亲水性,而PANI纳米纤维的加入则可以使膜孔隙率增大、表面孔径尺寸降低、皮层变薄。实验进一步发现,两种添加剂在改善膜结构与性能上起协同作用。PANI-F127一方面提高了膜纯水通量与抗污染性能,另一方面克服了单独使用Pluronic F127时添加量大、截留率低、添加剂易流失的缺点。