Removal of dyes by poly(p-phenylene terephthamide)/polyvinylidene fluoride hollow fiber in-situ blend membranes

In order to obtain the compatible poly(p-phenylene terephthalamide) (PPTA)/polyvinylidene fluoride (PVDF) blend membranes, the casting solution was synthesized via the in situ polycondensation process and flat sheet blend membranes were successfully prepared through the immersion precipitation phase inversion method in our previous study. In this study, the polycondensation solution was directly used as the spinning dope to fabricate PPTA/PVDF hollow fiber in-situ blend membrane by the dry-wet spinning technique. Hollow fiber membranes were employed to remove the dyes including Congo red (CR) and methylene blue (MB) from the dyeing liquor. Effects of operation conditions on dye rejection and membrane water flux were investigated. With the increase of operation pressure, feed concentration and feed temperature, dye rejection rates gradually decreased, but the rejection value of CR and MB still remained above 99.5%. On the contrary, the permeation water flux basically increased. During the continuous dye filtration of 300 min, hollow fiber membrane can maintain high dye rejection rates and stable water flux. The combination method of physical backwashing and chemical cleaning can effectively alleviate membrane fouling and recover membrane water flux. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48569.     

Fabrication of harsh environment-tolerant and robust reinforced poly (tetrafluoroethylene) hollow fiber membranes with optimal heat setting technology

The high-temperature industrial waste oil treatment has put forward new requirements for membrane materials. Poly (tetrafluoroethylene) (PTFE) is regarded as the excellent membrane material for membrane process, due to its excellent properties. Herein, the reinforced PTFE hollow fiber membrane (PTFE-HFM) was prepared by the combination of wrapping and heat setting technology. The objection of this study was focusing on the outstanding chemical and thermal resistance of PTEF-HFM for overcoming harsh waste oil treatment. PTFE-HFM exhibited better chemical resistance in the experiment of acid and alkali compared to PVDF-HFM, which the surface of PVDF-HFM corroded obviously and none of PTFE-HFM. The pore size and porosity were precisely adjusted by heat setting technology. Firstly, the morphologies of PTFE-HFM was investigated by scanning electron microscopy, which exhibited favorable interfacial bonding state between PTFE separation layer and supporting layer. Subsequently, the prepared membranes exhibited high-temperature waste oil permeability of 195 L m⁻² h⁻¹ bar⁻¹with only 3% attenuation in long-term operation. Besides, the rejection of lubricants contained activated carbon also reached to 99%. Overall, the facile preparation and excellent performance of robust reinforced PTFE-HFM highlights its great potential in treating high-temperature waste oil.     

Dual layer composite nanofiltration hollow fiber membranes for low-pressure water softening

Nanofiltration (NF) membrane process has become increasingly attractive due to their unique characteristics to selectively remove specific compounds or ions. The most commonly NF membranes are negatively charged which is unsuitable for hardness removal. Therefore, the development of novel NF membranes with a positively charged skin has become a key issue for low pressure water softening.     

Preparation and performance of braid‐reinforced poly(vinyl chloride) hollow fiber membranes

A novel braid‐reinforced (BR) poly(vinyl chloride) (PVC) hollow fiber membrane was fabricated via dry‐wet spinning process. The mixtures of PVC polymer solutions were uniformly coated on the tubular braid which contained polyester (PET) and polyacrylonitrile (PAN) fibers. The influences of braid composition on structure and performance of BR PVC hollow fiber membranes were investigated. The results showed that the prepared BR PVC hollow fiber membranes were composed of two layers which contained separation layer and tubular braid supported layer when the PET and PET/PAN hybrid tubular braids were used as the reinforcement. But the sandwich structure appeared when the PAN tubular braid was used as the reinforcement, which revealed outer separation layer, tubular braid supported layer and the inner polymer layer. The BR PVC hollow fiber membranes that prepared by PET/PAN hybrid tubular braid had favorable interfacial bonding state compared with the membrane prepared by pure PET or PAN tubular braid. The pure water flux of the BR PVC hollow fiber membranes that prepared by the PET/PAN hybrid tubular braid were lower than that prepared by pure PET or PAN tubular braid, but the rejection of Bovine serum albumin was opposite. The tensile strength of prepared BR PVC hollow fiber membrane was higher than 50 MPa. Both of the tensile strength and elongation at break decreased with the increase of the PAN filaments in the PET/PAN hybrid tubular braid. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45068.     

中空纤维渗透汽化膜分离研究现状与展望

本文综述了中空纤维渗透汽化膜分离的研究进展,包括中空纤维支撑膜的制备、复合膜的制备方法、中空纤维渗透汽化膜的工业应用和中空纤维渗透汽化膜传质特性等几个方面,对这个方面所存在的问题以及今后发展方向进行了展望.     

Insight into fouling behavior of poly(vinylidene fluoride) (PVDF) hollow fiber membranes caused by dextran with different pore size distributions

Membrane fouling is the key problem that occurs in membrane process for water treatment. However, how membrane microstructure influences the fouling behavior is still not clear. In this study, fouling behavior caused by dextran was deeply and systematically investigated by employing four poly(vinylidene fluoride)(PVDF)membranes with different pore sizes, ranging from 24 to 94 nm. The extent of fouling by dextran was accurately characterized by pore reduction, flux decline, and the change of critical flux. The result shows that membrane with the smallest pore size of 24 nm experienced the smallest fouling rate and the lowest fouling extent. As the membrane pore size increased, the critical flux ranges were 105-114, 63-73, 38-44 and 34-43 L·m~(-2)·h~(-1),respectively. The critical flux and fouling resistances indicated that the fouling propensity increases with the increase of membrane pore size. Two pilot membrane modules with mean pore size of 25 nm and 60 nm were applied in membrane filtration of surface water treatment. The results showed that serious irreversible membrane fouling occurred on the membrane with pore size of 60 nm at the permeate flux of40.5 L·m~(-2)·h~(-1).On the other hand, membrane with pore size of 25 nm exhibited much better anti-fouling performance when permeate flux was set to 40.5,48 and 60 L·m~(-2)·h~(-1).     

Characterization of crosslinked hollow fiber membranes

As the applications for polymeric membranes expand, new challenges arise. One of the largest of these challenges is the plasticization caused by strongly swelling penetrants such as carbon dioxide at elevated pressures. A considerable amount of material research has investigated crosslinking of dense film membranes to increase plasticization resistance. This paper extends such materials research to include more practically relevant asymmetric hollow fibers. Crosslinkable polyimide fibers were spun and an ester crosslinking reaction was studied using chemical and spectroscopic techniques to characterize the extent of crosslinking and to relate the effect of the reaction on fiber stability. CO₂ permeance and CO₂/CH₄ selectivity were studied at a variety of pressures and temperatures over time to yield indications of real-world separation performance.     

Poly(vinylidene fluoride) hollow‐fiber membranes containing silver/graphene oxide dope with excellent filtration performance

In this study, an antifouling poly(vinylidene fluoride) (PVDF) hollow‐fiber membrane was fabricated by blending with silver‐loaded graphene oxide via phase inversion through a dry‐jet, wet‐spinning technique. The presence of graphene oxide endowed the blended membrane with a high antifouling ability for organic fouling. The permeation fluxes of the blended membrane was 3.3 and 2.9 times higher than those of a pristine PVDF membrane for filtering feed water containing protein and normal organic matter, respectively. On the other hand, the presence of silver improved the antibiofouling capability of the blended membrane. For the treatment of Escherichia coli suspension, the permeation flux of the blended membranes was 8.2 times as high as that of the pristine PVDF membrane. Additionally, the presented blended membrane improved the hydrophilicity and mechanical strength compared to those of the pristine PVDF membrane, with the water contact angle decreasing from 86.1 to 62.5° and the tensile strength increasing from 1.94 to 2.13 MPa. This study opens an avenue for the fabrication of membranes with high permeabilities and antifouling abilities through the blending of graphene‐based materials for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44713.     

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。     

聚偏氟乙烯中空纤维膜的耐辐射性能研究

研究了较低剂量的γ辐射对聚偏氟乙烯中空纤维膜的结构与性能的影响。在试验中,选用44.57 Gy/min的剂量率,分别采用2,4,6,10 kGy剂量对浸泡在pH=10的氢氧化钠溶液中的中空纤维膜进行辐照。对辐照前后的样品作相关的性能测试,结果表明:随着辐射剂量的增加,透水通量先增大后减小,最大孔径持续减小,最大幅度至14.9%,分离性能增强。在≤10 kGy的剂量内,断裂强力呈现增大趋势,断裂伸长率呈现下降趋势,爆破强度先增大后减小。工艺优化的剂量为2 kGy。微观形貌和红外分析表明,辐射对膜的外表面化学基团及内表面的形貌产生一定的影响。热分析表明,辐照使膜的结晶度有所提高。     

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.     

Hollow fiber microfiltration membranes from poly(ether ether ketone) (PEEK)

A procedure for obtaining high performance large internal diameter (ID; >1 mm) hollow fiber microfiltration membranes from poly(ether ether ketone) (PEEK) is presented. A simple mixture of isomers of diphenylphthalate is a good solvent for employing the thermal‐phase inversion process to obtain PEEK membranes. Obtaining large ID hollow fibers with substantial transmembrane flux requires sufficient melt strength during spinning to prevent excessive draw of the extruding fiber. The use of a second leachable polymer to the blend satisfies the conditions, and polysulphone (PS) is found to provide superior membranes relative to either poly(etherimide) (PEI) or poly(ether sulphone) (PES) as a second polymer. PEEK membranes obtained by this process yield better chemical resistance to a concentrated warm surfactant/oil solution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 175–181, 1999     

对称型复合中空短纤维纺丝生产技术

探讨对称型复合中空纤维纺丝的生产技术。该产品技术利用了2种不同性能的熔体在同样的纺丝外界条件下具有不同的收缩性,从而形成天然永久性的立体三维卷曲。对关键技术如熔体的特性黏度,复合组件,中心吹风参数等进行了探讨。     

Preparation of poly(phthalazinone ether sulfone ketone) hollow fiber membrane for gas separation

Poly(phthalazinone ether sulfone ketone) (PPESK) asymmetric hollow fiber membranes for gas separation were prepared by dry/wet phase inversion technique. The effects of various preparation conditions such as solvent, nonsolvent-additives(NSA), PPESK concentration, and air gap on the membrane performance were studied. The heat resistance of the PPESK hollow fiber membrane was also examined. The hollow fiber membrane prepared from solvent with stronger solubility showed low gas permeation and high O₂/N₂ selectivity due to the denser skin layer. Hollow fiber membrane made from PPESK/DMAc/EtOH/THF system had thicker skin layer than that made from PPESK/DMAc/GBL system with the same ratio of near-to-cloud-point of NSA, which resulted in the higher O₂/N₂ selectivity. Along with the increase of NSA content, the gas permeation increased and the O₂/N₂ selectivity decreased. The O₂/N₂ selectivity of hollow fiber membranes made from PPESK/DMAc/GBL and PPESK/DMAc/EtOH/THF systems were 4.9 and 4.8 respectively, when the membrane forming systems contained appropriate content of NSA. The high polymer concentration resulted in low gas permeation and high O₂/N₂ selectivity. When the air gap was excessively long, the membrane performance dropped because of the damage to the dense skin layer. There was no significant drop on the membrane performance when the operation temperature was elevated to 90°C. The average O₂/N₂ selectivity was higher than 3.0 at 70°C during a long period of 55 days' test time. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Permeate pressure build-up in shellside-fed hollow fiber pervaporation membranes

Pervaporation of water, ethanol and isopropanol through polydimethylsiloxane hollow fiber membranes was studied, with emphasis on elucidating the significance of permeate pressure build-up inside the fibers when the shell-feed mode of operation was used. The differential form of the Hagen-Poiseuille equation was used to describe the permeate pressure profile, and the theoretical predictions of permeate productivity were confirmed by experimental data. A parametric analysis showed that the dimensions of the hollow fiber (inside and outside diameters, and length) significantly affected the overall pervaporation performance of a hollow fiber membrane module, and the fiber dimensions must be optimized in order to achieve high productivity.     

Teflon AF2400/Ultem composite hollow fiber membranes for alcohol dehydration by high‐temperature vapor permeation

High‐temperature vapor permeation has a stringent requirement of membrane stability under harsh feed environments. This work reports the design of Teflon AF2400/Ultem composite hollow fiber (HF) membranes for alcohol dehydration via vapor permeation. Fabrication parameters such as Teflon concentration and coating time were systematically investigated. Interestingly, the fabricated composite HF membranes possess an unusual surface with honeycomb‐like microstructure patterns. Owing to the Teflon protective layer, the newly developed composite HF shows a promising and stable separation performance with a flux of 4265 gm^?2 h^?1 and a separation factor of 383 for 95% isopropanol dehydration at 125°C. The composite HF also performs well under extreme vapor feed compositions from 87 to 99 wt % isopropanol. In addition, it exhibits impressive separation performance for the dehydration of ethanol and n‐butanol. This work may provide useful insights of designing thermal‐stable and high‐performance composite polymeric membranes for vapor permeation. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1747–1757, 2016     

水蒸气在中空纤维复合膜中渗透的微分阻力模型

建立了水蒸气在中空纤维复合膜中渗透的微分阻力模型,用实验验证了模型的可靠性。采用该模型估算出中空纤维膜的结构参数,研究了水蒸气在各层膜中的阻力,并以H2O/C2H2系统为例,考察了膜的结构参数对H2O/C2H2选择性的影响。     

Preparation of ZnO-glass composite hollow fiber and its application in formation of ZIF-8 membrane

The sintering temperature of ZnO ceramic hollow fibers (HFs) is generally up to 1400°C and presents a major challenge to obtain HFs with high permeability and mechanical strength at lower sintering temperature. This work proposed a glass powder-assisted method to reduce the sintering temperature by using their adhesive property. ZnO-glass composite HFs with longer finger-like channels, high permeability (3.12 × 10⁻⁵–9.1 × 10⁻⁶ mol·m⁻²·s⁻¹·Pa⁻¹) and good mechanical strength (42.12–52.75 MPa) were obtained at sintering temperature of 1150°C. More glass powders can generate stronger bonding effect during the ZnO particles, resulting in a decrease in porosity and an increase in the mechanical strength of ZnO-HF. These ZnO-HFs were further applied for inducing ZIF-8 membranes by one-step solvothermal growth. ZnO not only provides the growth and nucleation centers but also acts as transitional bridge to make the ZIF embed into support to improve the bonding force between membrane and support. Therefore, HF-supported-ZIF-8 membrane exhibited both mechanical and thermal robustness by maintaining their gas separation performance during the 30-min sonication treatment and 50-h operation testing at 25–200°C. Furthermore, this membrane provided good reproducibility. This work opens prospects for preparing ceramic HFs at lower sintering temperature and their functional applications as well as the preparation of MOF membranes.     

镍基非对称中空纤维膜用于乙醇自热重整制氢

采用纺丝-烧结技术制备了具有内表面致密皮层的外支撑式金属镍非对称中空纤维膜,并用于乙醇自热重整（EATR）制氢,研究了温度、进料流速、吹扫气流速、水醇比（S/C）以及氧醇比（O₂/C）等操作条件对膜制氢性能的影响。结果表明,金属镍非对称中空纤维膜既具有优异的EATR催化活性,又有良好的透氢性能。在500～1000℃、S/C=4、O₂/C=0.8的条件下乙醇可完全转化,H₂产率和H₂渗透通量可分别达到81.59%和13.99 mmol/（m²·s）,增加进料中氧气含量可显著抑制膜表面积炭,但同时也会降低氢气产率和一氧化碳选择性。