Comparative behavior of PVA/PAN and PVA/PES composite pervaporation membranes in the pervaporative dehydration of caprolactam

Flat‐sheet composite membranes were developed by the traditional phase inversion technique using poly;(vinyl alcohol) (PVA). PVA composite pervaporation (PV) membranes were prepared with crosslinked PVA selective layer and porous polyacrylonitrile (PAN) and polyether sulfone (PES) substrate layer material as supports for separating heat sensitivity substance ε‐caprolactam (CPL) from CPL/water mixtures. Glutaraldehyde was used as crosslinking agent. The effect of the composition of glutaraldehyde on membrane stability and structure were investigated. The operating parameters, such as feed concentration and operating temperature, remarkably affected PV performance of the composite membranes. The composite membranes with PVA casted on PAN (PVA/PAN) showed superior PV performance than that casted on PES (PVA/PES). This study has also shown that the type of porous support plays an important role in the PV performance. As a result, this work has presented the information needed of the behavior of PV membranes for dehydration applications of industrial caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4005–4011, 2007     

Preparation and characterization of CMCS/PVA blend membranes and its sorption and pervaporation performance (I)

Novel pervaporation (PV) membranes for ethanol dehydration were prepared by blend poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMCS), followed by the crosslinking reaction with glutaraldehyde; the structure and miscibility of the blend membranes were characterized by Fourier transform infrared, X‐ray diffraction, and differential scanning calorimetry; the results indicated that the blends were miscible. The effect of feed concentration, operation temperature, crosslinking agent content, etc. on sorption performance and PV performance of the blend membrane is investigated. The membrane of CMCS/PVA blend ratio of 8 : 2 exhibited a high separation factor of 2959 with a reasonably high water flux value of 0.14 kg m^?2h^?1 at the azeotropic feed composition (95 wt % of ethanol) at a temperature of 45°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Cellulose triacetate/LUDOX-SiO2 nanocomposite for synthesis of pervaporation desalination membranes

A series of cellulose triacetate/Ludox-silica nancomposite pervaporation membranes was successfully prepared via solution casting, aiming to improve the performance of cellulose triacetate membranes for desalination. The fabricated nanocomposite membranes were characterized to study the membrane morphology, chemical composition, mechanical properties, and surface hydrophilicity. Furthermore, the desalination performance was investigated as a function of silica (SiO₂) loading (ranging from 1 to 4 wt%) and feed concentration at 30 and 60 g/L of sodium chloride (NaCl). Pervaporation experiments showed that incorporating 4 wt% SiO₂ into a cellulose triacetate (CTA) membrane increased the water flux by a factor 2.5 compared with pristine CTA (from 2.2 to 6.1 kg m⁻² h⁻¹) for a 30 g/L NaCl feed solution at 70°C, while the salt rejection remained above 99%. The CTA/4 wt% SiO₂ membrane was found to have only 21% flux reduction when tested with a 60 g/L NaCl feed solution, without changes in membrane selectivity. This suggests that the developed CTA/Ludox-SiO₂ nanocomposite pervaporation membrane is suitable for desalination.     

PVA膜渗透汽化分离低浓度丙酮/水溶液的实验研究

采用聚乙烯醇（PVA）膜渗透汽化分离浓缩低浓度丙酮/水溶液,考察了原料液浓度、温度、膜后真空度等对PVA膜渗透通量和分离因子的影响。结果表明,随着原料液浓度的增加、温度和膜后真空度的升高,渗透通量和分离因子均呈增加的趋势,温度对渗透通量的影响基本符合Arrhenius方程。     

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     

Preparation and characterization of PVA/SA composite nanofiltration membranes

Nanofiltration (NF) composite membranes based on poly(vinyl alcohol) (PVA) and sodium alginate (SA) were prepared by coating PVA/SA (95/5 in wt %) mixture solutions on microporous polysulfone (PSF) supports. For the formation of a defect free thin active layer on a support, the PSF support was multi‐coated with a dilute PVA/SA blend solution. The PVA/SA active layer formed was crosslinked at room temperature by using an acetone solution containing glutaraldehyde as a crosslinking agent. The prepared composite membranes were characterized with a scanning electron microscopy (SEM), a Fourier transform infrared spectroscopy (FTIR), an electrokinetic analyzer (EKA) and permeation tests: The thicknesses of the active layers were about 0.25 μm and 0.01 μm depending on the preparation conditions. The crosslinking reaction of the active layers were completed in less than three minutes via the formation of acetal linkage. The surface of the PVA/SA composite membrane was found to be anionic. The permeation properties of the composite membrane were as follows: 1.3 m³/m² day of flux and > 95% of rejection at 200 psi for 1000 ppm PEG600 solution. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 347–354, 2000     

Dehydration of tetrahydrofuran by pervaporation using crosslinked PVA/PEI blend membranes

Dense blend membranes were prepared by blending hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(ethyleneimine) (PEI), which were then crosslinked by glutaraldehyde (GA) in a mixture of solvents under the catalysis of hydrochloric acid (HCl) for the dehydration of tetrahydrofuran (THF) by pervaporation. The effect of experimental parameters such as feed water concentration, permeate pressure, and membrane thicknesses on permeate parameters, i.e., flux and selectivity were determined with feed water concentration less than 40 wt %. The membranes were found to have good potential for breaking the azeotrope of 94 wt % THF with a flux of 1.072 and 0.376 kg/m² h for plane PVA/PEI and crosslinked PVA/PEI blend membrane, which exhibited high selectivity of 156 and 579 respectively. Selectivity was found to improve with decreasing feed water concentration and increasing membrane thickness, whereas flux decreased correspondingly. High permeate pressure causes a reduction in both flux and selectivity. These effects were clearly elucidated with the aid of the known relationship among plasticization effect, degree of swelling, permeate pressure, and feed water concentration. These blend membranes were also subjected to sorption studies to evaluate the extent of interaction and degree of swelling in pure as well as binary feed mixtures. Further ion exchange capacity studies were carried out for all the crosslinked and uncrosslinked membranes to determine the total number of interacting groups present in the membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1152–1161, 2006     

季铵盐烷基醚化阳离子聚乙烯醇制备及性能

引言 渗透汽化膜分离法可分离恒沸物、热不稳定体系、节能环保,日益被重视.渗透汽化过程的核心是分离膜,膜材料的选择、改性及制备是影响膜分离性能的重要因素.近年来,聚电解质复合物(polyelectrolyte complex,PEC)渗透汽化膜的研究有了较大进展.PEC是将聚阳离子和聚阴离子通过库仑力结合形成的[1].PEC膜具有良好的机械性能,对水及水溶性小分子表现出高透过性[1].本文以聚乙烯醇(PVA)、(3-氯-2-羟丙基)-3-甲基氯化铵为原料,制备了一种QAPVA新型聚阳离子电解质.将其与POAPVA聚阴离子电解质制备PEC膜,用于分离醇/水体系,取得了满意的分离效果.     

渗透蒸发膜改性技术的研究进展

物理改性和化学改性作为改变渗透蒸发膜的分离性能 (渗透通量和分离因子 )、抗污染性、物理化学稳定性的有效手段而吸引了大量的研究和开发兴趣。这些改性方法在不少场合下可以联合使用。对常用的改性方法进行了分类介绍 ,简要评述了各种方法的优缺点 ,并列举了一些实例加以具体说明     

ZSM-5沸石分子筛膜的制备及脱盐性能研究

淡水资源日益短缺,发展膜法海水淡化技术是满足世界淡水供应需求的重要途径,但是寻找合适的膜材料依然是人类面临的挑战。ZSM-5沸石分子筛膜（简称沸石膜）具有规则的孔道结构、合适的孔径尺寸（0.51~0.56 nm）以及可调变的硅铝比,在有机物脱水分离应用中展示了优异的选择性及良好的渗透性和稳定性。基于其孔径尺寸介于水分子和盐离子之间,其在海水淡化脱盐领域也具有应用潜力。在大孔α-Al₂O₃载体上采用二次生长法制备了ZSM-5沸石膜,考察了晶化时间与合成液的硅铝比对ZSM-5沸石膜成膜和渗透蒸发脱盐性能的影响,并采用XRD、SEM、EDS与水接触角表征了合成膜的相结构与结晶度、骨架组成表面特性等膜的结构性质。结果表明：通过二次水热法采用合成液摩尔配比为n（Al₂O₃）∶n（SiO₂）∶n（Na₂O）∶n（NaF）∶n（H₂O）=0.05∶1∶0.21∶1.01∶55的合成液在175℃下晶化48 h为最佳的合成条件,制备了Si/Al比为10、接触角为17.5°的亲水纯相致密ZSM-5沸石膜,并在75℃下对3.5%（质量）的NaCl水溶液进行了渗透蒸发测试,水的通量和盐离子截留率达到8.35 kg·m^-2·h^-1和99.99%,且性能在60 h的时间依存性测试后依然稳定,表现出了很高的海水淡化工业应用潜力。     

CS/PVA-GA渗透蒸发膜分离偏二甲肼/水体系的实验研究

将壳聚糖(CS)和聚乙烯醇(PVA)按一定比例共混,再以戊二醛(GA)交联,制备CS/PVA-GA共混交联膜,研究了共混交联膜的结构、力学性能以及在偏二甲肼/水体系中的渗透蒸发脱水性能。结果表明,CS与PVA共混、GA交联,形成了致密的空间网状结构,随PVA含量增加,膜的抗张强度降低,而断裂伸长率增加。料液浓度、温度、膜厚度等因素对膜的渗透蒸发性能有较大影响,当料液中偏二甲肼的质量分数为50%,温度为20℃,渗透侧压力为100 Pa,膜厚约为25μm时,CS/PVA-GA共混交联膜的分离因子达到243,渗透通量可达167 g/(m2.h)。     

Preparation and characterization of PSSA/PVA catalytic membrane for biodiesel production

Poly(styrene sulfonic acid) (PSSA)/Poly(vinyl alcohol) (PVA) blend membranes prepared by the solution casting were employed as heterogeneous acid catalysts for biodiesel production from acidic oil obtained from waste cooking oil (WCO). The membranes were annealed at different temperature in order to enhance their stability. The structure and properties of the membranes were investigated by means of Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), X-ray diffraction (XRD). It is found that the crosslinking structure among PVA and PSSA chains formed when the thermal treatment temperature was higher than 80 °C. The retention of PSSA in the blend membranes in the methanol/water solvent was markedly increased from 50% to 85% with the increase of the annealing temperature from room temperature (for the untreated membrane) to 150 °C due to the formation of the crosslinking structure. The results of esterification of acidic oil show that the conversion was slightly improve with the PVA content in the membrane at a fixed PSSA content. The thickness of the catalytic membrane had no significant effect on the conversion in the end. The membrane annealed at 120 °C exhibited the best catalytic performance among the membranes, with a stable conversion of 80% with the runs.     

耐溶剂聚酰亚胺/陶瓷复合膜的制备及性能表征

采用3,3',4,4'-二苯酮四羧酸二酐(BTDA)、4,4'-二氨基二苯基甲烷(MDA)和4,4'-二氨基联苯(Bz)按一定比例共聚合成了一类新的共聚型聚酰亚胺(PI-BTDA/MDA/Bz),通过调整MDA和Bz的比例制备了4种具有不同化学结构的聚酰亚胺均质膜,测试了这些聚酰亚胺均质膜对水的接触角和在N,N-二甲基甲酰胺中的溶胀性。实验结果表明:BTDA、MDA、Bz的摩尔比为5:4:1时,所得的聚酰亚胺均质膜亲水性最好,且耐溶剂性能最优。以此比例的聚酰胺酸为铸膜液,0.2mm孔径的Al₂O₃陶瓷膜片为支撑体,制备了聚酰亚胺复合膜,并考察了进料温度和进料浓度对复合膜分离性能的影响。     

丙烯酰胺改性玉米淀粉/PVA复合膜的制备与表征

为了改善聚乙烯醇（PVA）膜的机械性能,选用玉米淀粉为原材料,50℃条件下以过硫酸铵和尿素为引发剂,同时加入丙烯酰胺对淀粉进行接枝改性,制备得到丙烯酰胺改性的玉米淀粉/PVA复合膜。其中,优化改性淀粉的接枝率确定最佳合成条件为淀粉/丙烯酰胺的质量比为3∶7、引发剂过硫酸铵占单体总质量的0.5%、尿素占单体总质量的0.5%。进一步利用优化的改性淀粉为改性剂,制备了系列改性玉米淀粉/PVA复合膜。采用傅里叶红外光谱、扫描电子显微镜（SEM）对复合膜的组成与结构进行表征,同时测定复合膜的机械性能、耐水性、耐热性等物化特性,结果表明30%ST-0.50%APSU改性淀粉的单体转化率为95.0%,接枝率为85.2%。 30%ST-0.50%APSU/PVA复合膜的耐热性能轻微下降,但断裂伸长率提高了256%,耐水性能提高了43.1%。     

含甲基纤维素的NaA沸石膜的制备和表征

NaA沸石膜具有规则的孔道结构,利于分子传输,在有机物脱水领域有一定的应用。为使沸石膜生长更连续均匀,提高渗透汽化性能,本文以甲基纤维素作为空间限制剂加入合成液,探究碱度、晶化温度以及晶化时间对膜的影响,按最优条件制备合成液,并依据质量比m(MC)∶m(H₂O)=1∶100添加甲基纤维素,制备NaA沸石膜。表征方法采用XRD、SEM和渗透汽化3种方式,结果表明添加甲基纤维素的沸石膜表面结构完整,生长致密且性能优良,在75℃下对0.6mol/L的NaCl水溶液做渗透汽化测试时,通量达8.33kg/(m²·h),盐离子截留率为99.95%。在0.6mol/L的NaCl的水溶液中测试72h,结果表明添加甲基纤维素的NaA沸石膜时间依存性更好,通量保持在8.30kg/(m²·h)左右,离子截留率稳定在99.90%。渗透汽化分离ω(C₂H₆O)=90%乙醇的水溶液,随着温度从60℃升高到75℃,沸石膜的通量由1.55kg/(m²·h)升高到2.56kg/(m²·h),渗透侧水含量保持在99.90%左右。     

中空纤维渗透汽化复合膜及组件研究进展

中空纤维渗透汽化膜组件具有器件小型化及成本较低等方面的优势,其工业应用潜力巨大。本文介绍了中空纤维渗透汽化复合膜及组件的研究进展,阐述了膜材料、成膜方法以及组件结构参数等对组件渗透汽化性能的影响,并对中空纤维渗透汽化膜组件的中试研究进行了总结。通过组件放大及中试研究发现,中空纤维渗透汽化膜组件的装填密度、长度以及抽吸方式均会影响其下游侧的真空度,从而影响其渗透汽化性能。膜材料的分子设计、组件的结构参数优化以及耐溶剂耐高温封装将是中空纤维渗透汽化膜组件未来工业放大过程中的关键环节。     

PHBV/PVA复合膜的制备及其性能研究

采用静电纺方法制备聚羟基丁酸/戊酸酯共聚物(PHBV)纤维膜材料,通过调节纺丝液中无水乙醇的含量制备出形态均匀的PHBV静电纺纤维膜。用浇铸法将聚乙烯醇(PVA)涂敷在PHBV静电纺纤维膜上,制备PHBV/PVA复合膜,通过调节PVA的浓度及涂覆量,研究复合膜配比对其力学性能及过滤性能的影响。结果表明,当PVA浓度为8%,PHBV/PVA体积比为2/3时,得到最佳性能的PHBV/PVA复合膜,水通量达到996 L/(m2.h),截留率为86%。     

PA/ZIF-8/PVDF复合纳滤膜的制备及其性能

采用反向扩散法在聚偏氟乙烯(PVDF)基膜表面原位生长一层均匀、致密的金属有机骨架材料ZIF-8纳米晶体层,并进一步优化界面聚合反应,制备高性能聚酰胺(PA)/ZIF-8/PVDF复合纳滤膜.采用SEM、XRD、FTIR、AFM、XPS、水接触角测定仪以及固体表面Zeta电位仪对ZIF-8/PVDF复合膜及PA/ZIF-8/PVDF复合纳滤膜的组成、结构和形貌进行了表征,考察了ZIF-8亚层的生长对界面聚合反应、复合纳滤膜结构及性能的影响.结果表明,ZIF-8晶体亚层在PVDF膜表面的均匀连续生长改善了PA分离层与PVDF基膜的界面相容性,提高复合纳滤膜PA分离层的交联度.在0.6 MPa下,复合纳滤膜纯水通量可达24.05 L/(m2·h),对MgSO4、Na2SO4、NaCl和MgCl24种盐的截留率分别达到97.34％、93.57％、89.31％和85.16％,具有优异的抗污染性能.     

木质素磺酸钙/海藻酸钠渗透汽化膜的制备及性能调控

当前石化资源遇到储量有限、利用过程对环境不友好等挑战,生物质燃料乙醇作为一种替代性能源崭露头角。渗透汽化是一种分离乙醇的方式,节能、环保,开发天然高选择性渗透汽化膜成为研究热点之一。本文提出利用木质素磺酸钙（CaLS）的亲水性和成膜性,将其与天然多糖海藻酸钠（SA）进行共混,制备了不同CaLS含量的CaLS/SA交联膜。采用傅里叶红外、X射线衍射、接触角和扫描电子显微镜等方法对交联膜进行了表征和分析。结果表明,CaLS能与SA充分均匀混合,并且CaLS的加入能提高SA膜的亲水性。进一步考察了CaLS添加量和操作温度对10%水含量的乙醇溶液分离性能的影响,当CaLS/SA质量比为5%时,CaLS/SA交联膜分离因子达到2872,渗透通量达到796g/(m² · h),较纯SA膜分别提高了160%和70%,证实了CaLS在膜分离领域的应用潜力。     

全硅沸石/聚二甲基硅氧烷渗透汽化膜制备及分离性能

考察了全硅沸石/聚二甲基硅氧烷(PDMS)渗透汽化均质膜制膜液中国液比(质量比)对渗透汽化膜性能的影响,利用均匀设计优化方法对交联时间、交联温度、全硅沸石填充鼍和PDMS中b胶量等对膜分离因子的影响进行了研究,制备了对丁醇分离性能较高的渗透汽化均质膜.50℃下,分离原料液质量分数为1.6%的丙酮-丁醇-乙醇-水溶液时,...