疏水微孔膜的制备与改性

膜蒸馏是一种新兴高效的膜分离技术,具有重要的应用前景。膜蒸馏中所用的膜是多孔的和不被料液润湿的疏水膜。分离膜的制备是应用这一技术的关键。文章对膜蒸馏过程及疏水性微孔膜做了介绍。进一步综述了疏水性微孔膜的制备,成膜方法和膜的改性,最后对膜蒸馏在不同领域中的应用趋势作了分析。     

基于多孔陶瓷膜的脱硫废水负压式膜蒸馏实验

目前采用多孔陶瓷膜进行膜蒸馏的技术已有不少研究,但由于膜本身的亲水特性,需要在使用前进行疏水改性,这增加了工序和成本,且疏水性随着使用过程逐渐减弱。因此,提出一种基于多孔陶瓷膜的脱硫废水负压式膜蒸馏方法,直接采用亲水性多孔陶瓷膜,通过泵的抽吸作用使膜内溶液形成负压,以防溶液渗出膜外。为探究负压式膜蒸馏的传热传质机理,通过实验对比了亲、疏水多孔陶瓷膜在不同工况下的传递特性。实验结果表明：当膜内负压值小于膜孔内溶液毛细力时,亲、疏水多孔陶瓷膜的膜孔内分别为溶液输运和水蒸气输运;当空气流量为22L/min、废水温度和流量分别为50℃和11L/h时,亲水膜的渗透通量在1.9～3.9kg/(m²·h)之间,而疏水膜的渗透通量仅为0.13～0.25kg/(m²·h);亲、疏水多孔陶瓷膜的热效率分别在92%和55%左右,说明亲水性多孔陶瓷膜有着更高的热效率,陶瓷膜的较高热导率有利于提升亲水膜的膜蒸馏性能;脱硫废水流量对热质传递性能影响不大,随着空气流量或者废水温度的增加,膜渗透通量随之增加。     

纳米纤维素膜疏水化改性研究进展

近些年来,以纳米纤维素为原料制备出的柔性透明薄膜,因其优异的机械性能、可再生性、生物相容性等,在新型包装材料、透明电子元器件基底等领域展现出巨大的应用价值。然而在潮湿环境下,纳米纤维素膜如何维持高的机械性能,成为其在高附加值领域应用中一个重要又易被忽视的问题。先阐述了纳米纤维素膜以及天然亲水性对其隔绝和机械性能的影响,接着从化学改性、物理吸附、共混交联三种改性方法入手,综述了近些年来纳米纤维素膜疏水改性的研究与进展,以及不同改性方式对膜材料应用性能的影响。     

膜蒸馏用疏水膜材料的研究进展

主要介绍了膜蒸馏工艺中的膜材料的研究进展.首先简要叙述了膜蒸馏工艺的原理、特点和组件构型等内容;然后介绍了疏水膜和双疏膜在膜蒸馏中应用的现状和制备,最后探讨了膜蒸馏用膜材料目前存在的问题和未来可能的发展方向.     

十八烷基硅烷疏水改性PVDF膜的制备及膜蒸馏抗润湿性能

通过相转化法制备的聚偏氟乙烯(PVDF)膜,因致孔剂等添加剂在膜中的残留,导致膜疏水性有限,在膜蒸馏的长时间运行过程中容易被料液污染,失去分离能力。实验采用十八烷基三甲氧基硅烷(OTMS)对碱处理羟基化的PVDF中空纤维膜进行自组装疏水改性,用于提高膜的膜蒸馏抗润湿的能力。通过控制变量探究了OTMS浓度、OTMS自组装时间、热处理温度三个条件对疏水改性膜性能的影响。经过自组装疏水改性后,膜的接触角达到122.5°;在经过12 h质量分数3.5%的氯化钠(NaCl)溶液,2 h质量分数3.5%的NaCl溶液和0.1 mmol/L的十二烷基硫酸钠(SDS)混合溶液膜蒸馏测试中均表现稳定,通量和电导率保持不变,改性膜具有更好的抗润湿能力。     

疏水石墨烯膜的制备及其用于膜蒸馏脱盐的研究进展

膜蒸馏技术由于理论截盐率高、操作条件温和及对盐浓度灵敏度低等优势,在脱盐领域中展现出巨大潜力。近年来,人们开始关注石墨烯材料在膜蒸馏脱盐领域中的应用。本文首先概述膜蒸馏技术的基本原理及常用膜材料;接着介绍石墨烯的疏水性质和疏水石墨烯膜的制备;再详细综述石墨烯混合基质膜、石墨烯复合膜及石墨烯纯膜这三类疏水石墨烯膜在膜蒸馏脱盐中的应用;最后总结疏水石墨烯用于膜蒸馏脱盐面临的主要挑战及未来研究方向。     

疏水性单管陶瓷膜接触器在SO2吸收中的应用

对平均孔径200 nm的氧化锆陶瓷膜进行疏水改性与表征,并将其组装制成疏水性单管陶瓷膜接触器,采用清水作为低成本吸收液,开展了陶瓷膜接触器在废气脱硫方面应用的研究。比较了亲、疏水陶瓷膜接触器的传质性能,考察了进气流量、吸收液流量、进气浓度和吸收液温度等因素对SO₂脱除率和传质速率的影响,并对陶瓷膜接触器进行了长期稳定性测试。研究表明,疏水改性只改变陶瓷膜的表面性质（接触角达到132°）,对形貌结构影响较小;与未改性的陶瓷膜相比具有更高的脱硫效率和总传质系数。SO₂的脱除率和传质速率随吸收液流量的增加均增加;SO₂的脱除率随进气流量和进气浓度的增加而降低,但传质速率增加;吸收液温度的升高不利于SO₂的吸收;原料气中的CO₂对SO₂的脱除率影响较小。与传统的填料塔相比,陶瓷膜接触器具有更小的传质单元高度（HTU）值。陶瓷膜接触器脱硫效率高,可稳定操作,在废气脱硫方面具有良好的应用前景。     

膜蒸馏用疏水性微孔膜研究进展

从膜蒸馏传质传热方面分析了疏水性微孔膜的最佳性能参数,叙述了近年来适用于膜蒸馏过程的膜材料、制备方法以及超疏水改性方法,分析了不同构型的膜组件优缺点、膜组件内部结构对膜蒸馏性能的影响和一些新膜组件设计形式,介绍了膜蒸馏过程中的难点:膜污染和膜润湿;分析了膜污染和膜润湿的类型和原因和膜污染和膜润湿检测方法,并归纳了常见的预防和恢复措施,探讨了膜蒸馏技术的应用前景和研究发展方向,主要有膜蒸馏过程中膜污染和润湿机理的研究、抗污染润湿膜的开发及其工业化应用、膜蒸馏商用膜组件的设计及优化等。     

膜蒸馏法分离乙醇水溶液的研究

采用改性后的陶瓷膜管,对低浓度乙醇水溶液进行了膜蒸馏的试验研究.重点考察了膜蒸馏过程的操作参数对膜通量和分离因子的影响.试验结果表明,膜通量随着乙醇浓度、膜两侧温差和真空度的增加而增加;而分离因子则随乙醇质量分数、膜两侧温差和真空度增加而减少.     

亲水和疏水改性膜的抗结垢和润湿能力的对比

膜蒸馏过程受料液盐度的影响较小,可以处理高矿化度的矿井水,但膜污染和润湿制约其工业化应用。本文首次全面比较了两种商业化的疏水膜,即平板聚四氟乙烯（PTFE）和聚偏氟乙烯（PVDF）,以及分别进行亲水和疏水表面改性后制备的PVA-PAA/PTFE和Teflon/PVDF两种复合膜,在直接接触式膜蒸馏（DCMD）中浓缩饱和硫酸钙溶液时的结垢和润湿程度。重点分析了两种基膜和复合膜的结垢和润湿机理,探讨它们在矿井水浓缩中的应用潜力和最佳膜结构。实验结果显示,饱和硫酸钙浓缩过程中,膜表面结垢是主要影响因素,PTFE膜和PVDF膜尽管膜微观结构差别巨大,但抗结垢能力接近;Teflon/PVDF复合膜因其表面有滑移特性而表现出完美的抗结垢性能,PVA-PAA/PTFE复合膜尽管有致密的亲水表面,抗结垢能力并不强。     

Poly(vinylidene difluoride) Membrane Assisted by Modified ZnO/ZIF Nanoparticles for Membrane Distillation

Poly(vinylidene difluoride) (PVDF) polymeric membranes incorporated by synthesized hydrophobic agents were applied for membrane distillation. ZnO nanoparticles were modified with a silane coupling agent (n‐octyltriethoxysilane) and coupled by zeolite imidazole framework (ZIF)‐8 crystals. In particular, hydrophobic and porous membranes were prepared with ZIF crystals and modified ZnO/ZIF‐coupled nanoparticles. The influences of feed concentration and temperature of NaCl solution and seawater during filtration were evaluated. The hydrophobic modified membranes showed a higher permeate flux than pure PVDF membranes at different feed concentrations and feed temperatures. After modification, the porosity increased significantly and the contact angle became larger.     

Water Purification by Membrane Distillation Process

Abstract

The demineralization of water by membrane distillation (MD) has been investigated. In the first stage of investigations the tap water or boiled tap water was employed as a feed, and the water recovery coefficient exceeding 75% was achieved. The obtained concentrate was supplied to the second stage of MD installation. The quality of distillate was stable and practically independent of the feed concentration. The produced distillate has the electrical conductivity in the range of 1.4–2.5 µS/cm. The precipitation of salt deposit on the membrane surface was observed during the water demineralisation, especially in the first stage of MD. The membrane morphology and the composition of precipitate layer were studied using scanning electron microscopy coupled with energy dispersion spectrometry. The formed deposit caused clogging of the membrane surface (pores), and resulted in a gradual decline of the module efficiency. Moreover, the formation of the deposit on the membrane surface was the major reason of the partial membrane wettability.     

ACHEMA 2022: Membranes and Membrane Processes

Numerous companies working in the field of membrane development, membrane production, and membrane separation engineering were present at ACHEMA 2022. Compared to the last ACHEMA in 2018, there were fewer attending companies and only few new topics since development has been blocked partially by the pandemic situation and the subsequent restrictions of this years. Nevertheless, some new developments have been identified concerning process design as well as ceramic and polymeric systems.     

陶瓷多层选择膜工艺

综述了制取陶瓷微滤和超滤多层选择膜的6种工艺方法，并指出了膜层的结构特点。     

Hydrophobic Modification and Regeneration of Shirasu Porous Glass Membranes on Membrane Emulsification Performance

The effect of hydrophobic modification and regeneration of Shirasu porous glass (SPG) membranes was systematically investigated on the monodispersity of emulsions. The results showed that the hydrophobic modification and regeneration of SPG membranes had little influence on the monodispersity of emulsions, no matter how many modification and regeneration runs were operated. The emulsification runs affected the emulsification performance to a certain extent when hydrophobically‐modified SPG membranes were used for preparing water‐in‐oil (W/O) emulsions repeatedly. However, they almost did not affect the emulsification performance when regenerated hydrophilic SPG membranes were used for preparing oil‐in‐water (O/W) emulsions. The SPG membranes could be used repeatedly after hydrophobic modification or regeneration with almost the same emulsification performance as fresh or freshly‐modified ones. The results provided some valuable guidance for the repetitive use of SPG membranes to prepare monodisperse O/W and W/O emulsions.     

XDLVO理论在膜蒸馏有机污染机理研究中的进展

膜蒸馏是一种极具前景的水处理工艺,然而膜污染现象很大程度上阻碍了该工艺的广泛应用。从膜面有机污染形成机理的起源、疏水作用的引入、双电层力的修正以及膜面形貌参数的影响等方面,详细介绍了基于XDLVO理论的膜污染机理模型及其优化方法,并针对膜蒸馏系统特有的运行环境,提出了改进膜面形貌重构算法、引入涉及固液气三相的边界条件、分析污染物形态参数的影响、增加其他作用力分项等研究方向建议与展望。     

用于膜蒸馏的膜材料现状

综述了用于膜蒸馏的膜材料及其性能。阐述了聚四氟乙烯膜用于纯水及盐水物系的膜蒸馏性能。膜应用物系的广泛性及其截留性能；介绍了聚偏氟乙烯膜结构的非对称性，不同添加剂和非溶剂对其性能的影响；评述了聚丙烯平板膜及中空纤维膜的研制及应用现状，并比较了3种膜材料的性能及研制方法，同时对膜蒸馏膜材料的研究开发前景进行了展望。     

渗透模式影响纳米涂层修饰陶瓷微滤膜分离性能的研究

研究了膜分离技术处理含油废水存在因油滴变形引起的膜堵塞问题。为减少膜污染,使用在市场上销售氧化铝微滤膜孔道表面制备纳米ZrO2涂层,利用纳米涂层改变微滤膜的表面亲水憎油性,具有良好的效果。考虑其工业应用条件,重点研究了循环模式（模拟大量废水处理）和浓缩模式（模拟少量废水处理）对膜渗透通量的影响。结果表明：循环模式下料液的油浓度为恒定的,纳米涂层能有效提高微滤膜的渗透通量。膜面流速的增加在一定程度上能提高膜渗透通量,但超过一定程度后,增加不明显。当膜面流速为7m／s时,修饰陶瓷膜的最大渗透通量为280L／（m^2·h）,油截留率为96．4％。在浓缩模式下,料液的油浓度随渗透液的排出呈指数性增加,随着油浓度的增加,渗透通量持续衰减,油截留率持续上升。当油浓度达到一定程度后,修饰陶瓷微滤膜不能有效地实现稳定含油废水的油水分离。     

Reproducible Measurement Results in Organic Solvent Nanofiltration with Ceramic Membranes

Ceramic membranes are still quite innovative to organic solvent nanofiltration. Nevertheless, flux and rejection results obtained in filtration measurements seem to depend largely on the experimental procedure, membrane production batch and setup. Therefore, an experimental approach is described, which proved to provide reproducible and reliable results that may be used as data set to derive parameters in model development.     

新型膜分离技术——渗透蒸馏

渗透蒸馏是一种渗透过程与蒸馏过程藕合的新型膜分离技术.本文对渗透蒸馏过程及特点,渗透蒸馏过程的热力学、动力学原理,渗透蒸馏的膜和膜组件及其应用进行了论述.