STRUCTURE AND PROPERTIES OF COMPOSITE POLYURETHANE HOLLOW FIBER MEMBRANES

Composite polyurethane(PU)-SiO_2 hollow fiber membranes were successfully prepared via optimizing thetechnique of dry-jet wet spinning,and their pressure-responsibilities were confirmed by the relationships of pure water flux-transmembrane pressure(PWF-TP)for the first time.The origin for this phenomenon was analyzed on the basis of membranestructure and material characteristics.The effects of SiO_2 content on the structure and properties of membrane wereinvestigated.The experimental results indicated that SiO_2 in membrane created a great many interfacial micro-voids andplayed an important role in pressure-responsibility,PWF and rejection of membrane:with the increase of SiO_2 content,theability of membrane recovery weakened,PWF increased,and rejection decreased slightly.

CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization

Carbon dioxide(CO_2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite(TFC) hollow fiber membrane was developed by interfacial polymerization between 1,3–cyclohexanebis–methylamine(CHMA) and trimesoyl chloride(TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO_2/CH_4 separation performance. For CO_2/CH_4 mixture gas(30/70 by volume) test, the membrane(PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO_2 permeance of 25 GPU and the best CO_2/CH_4 selectivity of 28 at stage cut of 0.1. The high CO_2/CH_4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.

PREPARATION OF POLYVINYLIDENE FLUORIDE/POLYVINYL DIMETHYLSILOXANE COMPOSITE HOLLOW FIBER MEMBRANES AND THEIR SEPARATION PROPERTIES

Microporous polyvinylidene fluoride(PVDF)hollow fibre membranes were spun using the dry-wet phaseinversion method.By means of dip-coating technique,a uniform coating with thickness of around 5-12 μm of polyvinyldimethylsiloxane(PVDMS)was formed on the surface of porous PVDF hollow fibers.The structural parameters of PVDFsubstrate membrane were estimated by gas permeation test.Using N_2/O_2 as the medium,the separation properties ofPVDMS-PVDF composite hollow fiber membranes were also evaluated experimentally.The experimental data of bothpermeability and selectivity are in good agreement with the theoretical results predicted by the presented pore-distributionmodel.In order to obtain the compact composite membrane free of defects by the dip-coating technique,the thickness ofPVDMS skin must be higher than 5 μm.

Sodium alginate-polyvinyl alcohol/polysulfone (SA-PVA/PSF) hollow fiber composite pervaporation membrane for dehydration of ethanol-water solution

Using polysulfone （PSF） hollow fiber ultrafiltration membranes as the substrate, sodium alginate （SA） and polyvinyl alcohol （PVA） blend solutions as the coating solution, and maleic anhydride （MAC） as the cross-linked agent, SAPVA/PSF hollow fiber composite membranes were prepared for the dehydration of ethanol-water. The effects of different sodium alginate concentration in the coating solutions and different operating temperatures on pervaporation performance were investigated. The experimental results showed that pervaporation performance of the SA-PVA/PSF composite membranes for ethanol-water solution exhibited a high separation factor although they had a relatively low permeation flux. As SA concentration in SA-PVA coating solution was 66.7% and the operating temperature was 40 ℃, SA-PVA/PSF hollow fiber composite membrane （PS4） had a separation factor of 886 and flux of 12.6 g/（m^2·h）. Besides, SA-PVA/PSF hollow fiber composite membranes （PS3 and PS4） were used for the investigation of the effect of ethanol concentration in the feed solution on pervaporation performance.

Fabrication of a Polyamide/Polysulfone Hollow Fiber Composite Membrane

With microporous polysulfone hollow fiber as the substrate, a polypiperazine amide nanofiltration composite membrane was prepared by interfacial polymerization in trimesoyl hexane solution as oil phase and piperazine aqueous solution as water phase. The conditions of the preparation, such as concentrations of monomer solutions, reaction time and temperature, annealing treatment, etc., were investigated. The hollow fiber composite herewith obtained showed high performance with water fluxes over 40 L·m -2·hr -1 and MgSO4 rejection of 93% under a pressure of 0.40 MPa.

Fabrication of polymer/fluoride-containing salts blend composite membranes for CO_2 separation

Poly （N,N-dimethylaminoethyl methacrylate）-poly （ethylene glycol methyl ether methacrylate） （PDMAEMA-PEGMEMA） and cesium fluoride （CsF） were blended and used as the separation material of composite membranes.Hollow fiber composite membranes were fabricated by coating the blend on polysulfone （PSf） hollow fiber substrate.Introduction of fluorine ion improved the separation performance of the membrane.The concentration of coating solution was adjusted to obtain a membrane with high permeance.The composite membrane showed good performance with the CO2 permeance of 30.4 GPU （1 GPU=10-6 cm3 （STP）/（cm 2 s cmHg））,and selectivities to CO2/N2,CO2/CH4,CO2/H2 and O2/N2 of 47.2,37.6,1.75 and 4.70,respectively.Potassium fluoride （KF）,due to its low cost,was also used as a substitute of CsF to prepare composite membrane and the permeation data showed that CsF can be replaced by KF.The effect of operating temperature on the permeation properties of the composite membrane was also investigated.

Synthesis of polypiperazine-amide thin-film membrane on PPESK hollow fiber UF membrane

A new interfacial polymerization （IP） procedure is developed in order to synthesize polypiperazine-amide thin-film membrane on the inner surface of poly（phthalazinone ether sulfone ketone） （PPESK） hollow fiber ultrafiltration （UF） membrane. A hollow fiber composite membrane with good performance was prepared and studied by PT-IR and scanning electron microscopy.

Preparation of PFSA/PSf hollow fiber composite membranes with recovered PFSA for the pervaporation separation of EtOH/H_2O

Perfluorosulfonic acid/Polysulfone(PFSA/PSf) hollow fiber composite membranes have been prepared by dip-coating method using PSf ultrafiltration(UF) membrane as substrate with recovered PFSA.The composite membranes were applied to the pervaporation separation of 95% ethanol(EtOH)/H2O mixture.SEM images show that the thickness of the PFSA skin layer of the composite membranes is about 2 μm,much thinner than those of other PFSA composite membranes revealed in the literatures.Effects of annealing temperature,coating solution concentration and counter-ions of PFSA on the pervaporation performances of the composite membranes were investigated.The total flux decreases and separation factor increases with the increase of annealing temperature.The highest permeation flux of 3230 g m-2 h-1 and a separation factor of 5.4 is obtained for the composite membrane annealed at 80°C.The lowest permeation flux of 396 g m-2 h-1 and a separation factor of 27.7 is obtained for the composite membrane annealed at 160°C.The permeation performances of the PFSA/PSf composite membrane are evidently influenced by the counter-ions of PFSA.The flux sequence of the PFSA/PSf composite membranes with different counter-ions is H+】Li+】Ca2+】Mg2+】Na+】K+】Ba2+】Fe3+】Al3+,and the separation factor sequence is H+【Li+【Al3+【Na+【Mg2+【Ca2+【K+ 【Ba2+【Fe3+.The apparent activation energy △Eapp values of the composite membranes with different counter-ions were calculated by Arrhenius law.The sequence of △Eapp values for the membranes with monovalent counter-ions is Li+】Na+】K+.There are very little variations of △Eapp values between the composite membranes with three divalent counterions(Mg2+,Ca2+ and Ba2+),and the △Eapp values of the composite membranes with two trivalent counterions(Fe3+ and Al3+) are relatively high.

界面聚合法制备低压中空纤维纳滤复合膜

现有中空纤维纳滤膜在实际应用中能耗较高.采用干湿法纺丝技术制备聚砜(PSf)中空纤维超滤膜作为基膜,分别选用哌嗪(PIP)和均苯三甲酰氯(TMC)为水相单体和有机相单体,通过界面聚合工艺的优化,成功制备了低压中空纤维纳滤膜.用扫描电子显微镜和原子力显微镜对膜表面形貌进行表征,用傅里叶变换红外光谱仪和X射线光电子能谱仪分析膜表面的化学结构和元素组成,测试了复合膜的表面水接触角、Zeta电位、截留分子量和孔径分布,研究了单体浓度、界面聚合反应时间以及测试压力对复合膜性能的影响并确定了最佳的工艺条件.结果表明,优化的低压中空纤维纳滤膜具有低交联度的聚酰胺功能层,在0.2 MPa的测试压力下,纯水通量达到(16.0±0.4)L/(m^(2)·h),对质量浓度为1 g/L的盐溶液的截留率为Na_(2)SO_(4)(94.2%±0.9%)>MgSO_(4)(92.2%±0.9%)>MgCl_(2)(51.0%±0.5%)>NaCl(9.5%±0.3%),表现出优异的Na_(2)SO_(4)/NaCl选择性.

中空二氧化硅粒径对PAN纤维膜隔热性和柔软度的影响

为了探究隔热填充物中空二氧化硅(SiO_(2))粒径大小对静电纺丝制备的纤维膜导热系数和柔软度的影响,设计制备不同粒径的中空SiO_(2)微球;采用单轴静电纺丝的方法将中空SiO_(2)填充于聚丙烯腈(PAN)纤维膜中,制备中空SiO_(2)微球聚丙烯腈(PAN)复合纤维膜。利用扫描电子显微镜、透射电子显微镜、热常数分析仪等仪器对中空SiO_(2)微球形貌、复合纤维膜的形貌、导热系数和柔软度进行观察、测试和分析。结果表明:自制中空SiO_(2)微球、粒径均匀、形貌规整,且在纤维内部具有良好的分散性;少量添加中空SiO_(2)微球,即可以显著提高复合纤维膜的隔热性能,在同等体积含量下,减小粒径有利于增加复合纤维膜的隔热性能。与纯聚丙烯腈纤维膜导热系数0.0480 W(m·K)相比,填充了130 nm中空SiO_(2)微球的复合纤维膜导热系数为0.0359 W(m·K),降低了25%。且中空SiO_(2)微球粒径小,可以使复合纤维膜保持更高的柔软性。

分离有机/有机混合物的PVA、CA系列膜及其渗透汽化性能研究(Ⅱ)成膜条件对渗透汽化性能的影响

用溶剂完全蒸发法制备了PVA复合膜 .经对MTBE/MeOH混合物的分离实验得到了PVA复合膜的最佳成膜条件 ,即 :铸膜液中PVA、马来酸浓度分别为 7%、3% ,热处理温度130～ 15 0℃ .在 1%～ 2 %丙酮水溶液中浸泡处理 4～ 8h ,CTA中空纤维RO膜被改性成渗透汽化膜 .CTA中空纤维膜的分离性能优于其它醋酸纤维素系列膜 。

纳米氧化物粒子对PVDF中空纤维膜结构与性能的影响

采用相转化法制备纳米氧化物/聚偏氟乙烯复合中空纤维膜,讨论了纳米氧化钛和氧化铝粒子对PVDF膜结构和性能的影响.应用牛血清白蛋白截留实验、扫描电子显微镜、傅立叶红外光谱分别对不同膜的分离性能、微观结构和晶相组成进行了分析.结果表明,复合膜的性能与纯PVDF膜相比有显著地改善,其中纯PVDF膜、Al2 O3 /PVDF和TiO2 /PVDF复合膜对牛血清白蛋白的截留率分别为3 . 2 7%、6 7 .2 0 %和86 . 6 7%,复合膜的水通量则较纯PVDF膜分别提高2 . 3倍和2 . 6倍.氮气吸附实验测定的孔径分布进一步表明复合膜的孔径分布变窄,孔径变小.

聚酰胺纳滤中空纤维复合膜的制备及其性能研究

以聚砜为原料,初步纺制了一种具有特殊形态结构的聚砜中空纤维基膜,以哌嗪水溶液和均苯三甲酰氯正己烷溶液进行界面聚合,在基膜表面形成超薄脱盐功能层.文中讨论了聚合条件对膜性能的影响.实验确认,中空纤维膜对MgSO4具有较高的脱盐率(>90%)和较高的透水通量(40L·m-2·h-1)

中空纤维复合纳滤膜的研究进展

从基膜制备工艺、新型功能层材料、涂覆工艺和基膜与功能层间相互作用机理等4方面综述国内外中空纤维复合纳滤膜的研究进展,并对其制备方法中亟需深入研究的内容和其应用前景进行展望.

硅橡胶-聚砜中空纤维复合膜的制备及性能研究

主要讨论硅橡胶 -聚砜中空纤维复合膜的制备工艺 ,并对所制备的膜组件进行透气性能研究 .考察了涂膜液浓度、涂膜压力对膜组件性能的影响 ,发现过高的涂膜压力不利于组件富氧空气通量的提高 .

凝固浴组分对双凝固浴法制备PVDF膜结构和性能的影响

在内外凝胶浴中添加不同含量的溶剂,采用双凝固浴法制备了PVDF/PVP/DMAc中空纤维膜.通过膜形貌扫描电镜(SEM)表征,纯水水通量和牛血清蛋白(BSA)截留率测试实验,分析评价了凝固浴中溶剂含量对PVDF中空纤维膜结构与性能的影响.结果表明,凝固浴中溶剂含量增大会导致皮层孔隙率增多,而对亚层结构的影响各不相同.膜的纯水渗透通量变化无明显规律性,但BSA截留率保持相对稳定.当内外凝固浴中溶剂体积分数分别为30%和70%时,膜内部大孔发育良好,亚层疏松多孔,水通量分别为270L/(m2.h)和548L/(m2.h),显示了良好的渗透性能.

聚乙烯醇-海藻酸钠共混中空纤维复合膜用于异丙醇脱水

制备了以聚砜(PS)中空纤维超滤膜为底膜的聚乙烯醇(PVA)-海藻酸钠(SA)共混复合膜,并用于异丙醇脱水的研究。考察了PVA/SA配比、交联剂种类和浓度以及渗透汽化实验中的操作条件对膜性能的影响。在PVA/SA质量比为4/1、料液温度45℃、料液中异丙醇质量分数为90%时,复合膜的通量和分离因子分别为427g/(m2·h)和1727,并且根据实验数据和Arrhenius经验方程式,计算得出异丙醇渗透活化能为17 42kJ/mol。

PVDF-SiO_2中空纤维复合膜的制备和表征

采用相转化法制备聚偏氟乙烯(PVDF)-二氧化硅(SiO2)中空纤维复合膜,讨论了纳米SiO2粒子对PVDF膜结构和性能的影响。通过扫描电子显微镜、能谱、傅里叶红外光谱、热分析、材料试验、接触角测量和超滤实验分别对不同膜的微观结构、化学组成、热稳定性、机械强度、亲水性以及分离性能、抗污染能力进行了联合表征。结果表明:添加SiO2粒子有利于PVDF由α相向β相转变,复合膜的性能与纯PVDF膜相比有明显改善。当w(SiO2)=3%时,纳米颗粒分散较均匀,膜断裂强度为纯PVDF膜的2.7倍,纯水通量由81.6 L/(h.m2)提高到160.0 L/(h.m2),热稳定性、亲水性和抗污染性显著提高;但过高的SiO2含量(w>3%)会引起纳米颗粒团聚而导致膜的各项指标下降。

壳聚糖/聚砜复合中空纤维膜的制备及其CO_2/N_2分离性能研究

以壳聚糖(CS)为涂层材料,聚砜(PSf)为基膜材料,运用浸渍涂覆的方式制备了壳聚糖/聚砜复合中空纤维膜,考察了壳聚糖质量分数、涂覆时间以及操作温度和压力对CO2、N2的渗透分离性能的影响。结果显示,在聚砜基膜上涂覆壳聚糖材料后,可有效提高CO2/N2分离系数;CO2、N2的渗透速率符合Arrhenius关系式;CO2在复合中空纤维膜中的渗透由溶解-扩散和促进传递两方面主导,而N2的渗透符合溶解-扩散模型。

以无机盐前驱体制备中空纤维担载Al_2O_3/ZrO_2复合膜

以三氯化铝、氧氯化锆为原料,经离子交换溶胶-凝胶法在α-Al2O3中空纤维载体制备了Al2O3/ZrO2膜。应用XRD,SEM,BET等测试手段对膜的热稳定性、形貌、孔径及其分布进行了表征。XRD结果显示,复合膜的热稳定性比单一氧化铝或氧化锆有显著提高,在700℃～1000℃的范围内,复合膜的晶相均为四方相。扫描电镜结果表明,膜表面完整、无缺陷。气体渗透实验表明,担载膜具有一定的气体选择性,在0.1MPa下对H2/N2的分离因子分别为3.08。等温氮气吸附实验显示:700℃热处理后Al2O3/ZrO2复合膜呈双峰分布,在3.65nm和5.30nm处分别出现了极值点,孔容为0.12ml/g,比表面积为91.36m2/g。