聚四氟乙烯膜的表面改性研究进展

聚四氟乙烯(PTFE)是一种全氟化聚合物,由四氟乙烯(CF2=CF2)聚合而成,是一种线型热塑性聚合物。C-F键的强键能使其具备优异的化学稳定性、耐腐蚀性、高机械强度。但是,PTFE具有强疏水性。因此,在用PTFE微滤膜进行水处理时,膜污染严重,使其应用受到了极大的限制。为了提高PTFE膜的抗污染性能,使其得到广泛的应用。人们采用了各种改性方法,如化学改性、等离子体辐照、原子层沉积和高温熔化来表面改性PTFE膜,提高其抗污染性能。本文介绍了近年来聚四氟乙烯膜改性技术的研究进展。讨论了聚四氟乙烯改性方法的优缺点,并对聚四氟乙烯多孔膜的应用方向进行了展望。     

真空膜蒸馏海水淡化技术研究进展分析

真空膜蒸馏海水淡化运行压力低、截留率高、设备简单,可充分利用舰船动力系统冷却海水余热,有望用于新型舰船海水淡化装置研制。文中总结了真空膜蒸馏海水淡化主要特征、过程机理,分析真空膜蒸馏海水淡化过程的影响因素:膜疏水性与结构参数、海水温度与流速、操作真空度及膜污染,并在此基础上展望膜蒸馏海水淡化技术的未来研究方向。     

阻垢剂对海水淡化膜蒸馏试验的影响

采用直接接触式膜蒸馏技术进行海水淡化试验研究。在海水温度为55℃,循环水温度为20℃的条件下,考察了不同阻垢剂用量对膜蒸馏海水淡化的影响、工艺连续运行过程中膜通量和产水电导率随时间的变化情况,确定了膜蒸馏过程稳定运行的最优浓缩倍率。结果表明,阻垢剂的加入可明显提高淡水的产水率,产水率可达到85%以上,减少了高盐度海水浓缩液的排放,膜通量稳定,产水水质好,其电导率不超过10μS/cm,膜蒸馏海水淡化具有一定的技术可行性和可操作性。     

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。     

Al2O3平板陶瓷膜的工业化制备与应用展望

平板陶瓷膜作为一种新型膜材料,兼有有机膜和管式陶瓷膜的优点,不但具有很好的物理性能和化学性能,且制造和运行成本低,能够方便快捷的大规模应用。文中介绍了工业化制备的方法,由支撑体的制备和膜的制备两部分组成,制备出最可几孔径为0.11μm、翘曲率低的平板陶瓷膜产品。文中还展望了其在膜生物反应器、海水淡化预处理和饮用水预处理等领域的应用。     

陶瓷膜超疏水改性及其膜蒸馏性能研究

以聚苯乙烯(PS)和四氢呋喃(THF)的混合溶液为铸膜液,无水乙醇(Et OH)为非溶剂,通过非溶剂致相分离(NIPS)法在亲水性陶瓷膜表面构造超疏水性PS微孔膜,得到超疏水性陶瓷膜。考察PS与Et OH比例、浸渍时间对陶瓷膜疏水性和膜结构的影响,并通过浸没式真空膜蒸馏(SVMD)研究超疏水性陶瓷膜的脱盐性能。结果表明,超疏水改性后,PS沉积在陶瓷膜表面,减小了膜的平均孔径;当PS与Et OH的质量比为1:4,浸渍时间为3 min时,改性膜的水接触角达到152°,滚动接触角达到8°,达到超疏水效果,且在SVMD中的渗透通量最高,保持在1.57 kg/(m~2·h)左右,脱盐率高于99.5%。     

面向过程工业的陶瓷膜制备与应用进展

陶瓷膜具有优异的化学稳定性、机械稳定性及分离性能,在过程工业中获得了成功应用,成为我国膜领域中最有国际竞争力的膜品种之一。本文基于面向应用过程的膜材料设计的理论框架,系统概述了陶瓷膜的定量制备技术、面向应用体系的陶瓷膜选择与设计方法以及膜应用过程中污染控制的研究进展,并对未来我国陶瓷膜领域的发展态势进行了分析和研讨。     

太阳能膜蒸馏系统进展与展望

海水淡化技术可有效解决现有的淡水资源短缺等问题,但受限于高成本、高能耗、低热效率等因素,传统海水淡化工艺难以进一步推广。近年来,太阳能海水淡化作为一种高效低廉的海水淡化技术正逐渐进入人们的视野,其中,太阳能膜蒸馏技术更是凭借着适用范围广、蒸发效率高、能耗低、成本低廉等诸多优点为众多学者所青睐。各国学者从宏观的系统结构到微观的光热材料等方面展开了大量的工作。但由于膜蒸馏固有的温度极化以及膜污染等问题,太阳能膜蒸馏技术仍然处于发展瓶颈中。本文按照太阳能引入膜蒸馏装置位置的不同,对现有的诸多太阳能膜蒸馏系统进行分类,并针对各类太阳能膜蒸馏系统的发展现状和技术瓶颈进行详细阐述。探讨了当前太阳能膜蒸馏技术的局限性及未来的挑战,以期为太阳能膜蒸馏系统的进一步发展及应用提供参考。     

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。     

管式蒸馏海水淡化换热管强化技术发展探讨

为进一步提高淡化效率,阐述了管式蒸馏海水淡化系统的基本热质传递机理,叙述了国内外通过优化管型、表面改性(亲水、疏水)等提高换热管热质传递性能的研究进展,并分析了上述方法应用在管式蒸馏海上淡化系统中的优缺点。认为在改变管型的基础上对其进行表面亲水、疏水处理,既可以很大程度提高系统整体的热质传递,还能够避免清洗困难和清洗周期短的现象。随着表面改性技术的不断完善,且与优化管型相结合,在管式蒸馏海水淡化领域必将会拥有良好的应用前景。     

膜蒸馏海水淡化研究进展及发展趋势

海水淡化是解决我国水资源短缺的重要措施之一。膜蒸馏海水淡化技术可以充分利用太阳能等低品位热源，具有成本低、设备简单、操作容易、能耗低等优点，在海水及苦咸水淡化方面应用前景广阔。     

二硫化钼作为海水淡化材料的研究进展

海水淡化是从丰富的海水资源中提取清洁淡水的技术,是解决淡水资源短缺的重要途径。传统的海水淡化技术在实际应用中已经暴露出高成本、高能耗和低效率等缺点,因此开发海水淡化新兴技术及材料成为研究重点。二硫化钼（MoS₂）是典型层状过渡金属硫化物,因其化学稳定、吸光能力优异等优点,在海水淡化领域具有极大的应用前景。作为一种高效环保的海水淡化材料,MoS₂及其复合材料在改善传统脱盐工艺和发展新兴脱盐技术中已得到广泛研究。本文主要论述和分析MoS₂基材料在电容去离子、膜脱盐及太阳能脱盐等海水淡化应用中的研究进展以及在工业化应用中面临的挑战,并展望其今后在脱盐领域的发展方向。     

Distillation vs. membrane filtration: overview of process evolutions in seawater desalination

The worldwide need for fresh water requires more and more plants for the treatment of non-conventional water sources. During the last decades, seawater has become an important source of fresh water in many arid regions. The traditional desalination processes [reverse osmosis (RO), multi stage flash (MSF), multi effect distillation (MED), electrodialysis (ED)] have evoluated to reliable and established processes; current research focuses on process improvements in view of a lower cost and a more environmentally friendly operation. This paper provides an overview of recent process improvements in seawater desalination using RO, MSF, MED and ED. Important topics that are discussed include the use of alternative energy sources (wind energy, solar energy, nuclear energy) for RO or distillation processes, and the impact of the different desalination process on the environment; the implementation of hybrid processes in seawater desalination; pretreatment of desalination plants by pressure driven membrane processes (microfiltration, ultrafiltration and nanofiltration) compared to chemical pretreatment; new materials to prevent corrosion in distillation processes; and the prevention of fouling in reverse osmosis units. These improvements contribute to the cost effectiveness of the desalination process, and ensure a sustainable production of drinking water on long terms in regions with limited reserves of fresh water.     

Highly stable hydrophobic SiNCO nanoparticle‐modified silicon nitride membrane for zero‐discharge water desalination

Membrane distillation water desalination can attain a significantly higher water recovery than reverse osmosis, while the lack of stable hydrophobic membranes limits its commercial applications. This article presents the preparation of a new hydrophobic membrane by modifying a porous Si₃N₄ substrate with vesicular SiNCO nano‐particles. The membrane had a water contact angle of 142°, due to the presence of –Si–CH₃ terminal groups and the high surface roughness. The contact angle remained nearly the same after exposures of the membrane to boiling water, aqueous solutions with pH ranging from 2 to 12, and benzene. The membrane exhibited satisfactory water desalination performance on highly concentrated NaCl solutions and simulated seawater. With the highly stable membrane, it is promising to develop a zero‐discharge water desalination process for simultaneous production of fresh water for daily uses and brine for industrial uses. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1272–1277, 2017     

Utilization of solar energy for direct contact membrane distillation process: An experimental study for desalination of real seawater

Membrane distillation (MD), a non-isothermal membrane separation process, is based on the phenomenon that pure water in its vapor state can be extracted from aqueous solutions by passing vapor through a hydrophobic microporous membrane when a temperature difference is established across it. We used three commercially available hydrophobic microporous membranes (C02, C07 and C12; based on the pore size 0.2, 0.7 and 1.2 μm respectively) for desalination via direct contact MD (DCMD). The effects of operating parameters on permeation flux were studied. In addition, the desalination of seawater by solar assisted DCMD process was experimentally investigated. First, using solar power only short-term (one day), successful desalination of real seawater was achieved without temperature control under the following conditions: feed inlet temperature 65.0 °C, permeate inlet temperature 25.0 °C, and a flow rate of 2.5 L/min. The developed system also worked well in the long-term (150 days) for seawater desalination using both solar and electric power. Long-term test flux was reduced from 28.48 to only 26.50 L/m²hr, indicating system feasibility.     

Recent progress on low-cost ceramic membrane for water and wastewater treatment

Great progress in the development of low-cost ceramic membranes from alternative materials have been achieved recently towards various application especially water and wastewater treatment. However, their significance has not been fully recognized and understood especially in term of their microstructural analysis such as formation of grain growth and microcracks. This review paper summarizes fabrication method, alternative materials, microstructure, wettability, mechanical properties and application of low-cost ceramic membrane. The fabrication method including slip casting, tape casting, extrusion, pressing method and phase inversion technique are described. Alternative materials used in low-cost ceramic membrane fabrication are discussed and categorized into clays, agricultural waste, industrial waste and animal bone waste. The mechanisms of morphology formation, microstructure and wettability properties are analysed. Modification strategies for the surface of low-cost ceramic membrane are discussed, and classified into modification for separation application, modification for photocatalytic application and modification for membrane distillation and membrane contactor system. Modification improves the membrane structure by changing the pore size, porosity and wettability properties of low-cost ceramic membranes. Mechanical properties of low-cost ceramic membranes are also discussed in detail towards several mechanism, like grain growth phenomenon and formation of microcracks which also considered as membrane defects. Grain growth phenomenon can be divided into normal and abnormal grain growth. Meanwhile, formation of microcracks could be occurred in single-phase polycrystalline ceramics that have anisotropic grains or biphasic polycrystalline grains. The application of low-cost ceramic membrane in seawater desalination, oily wastewater treatment, heavy metal adsorption, textile separation and photocatalytic application are reviewed. Finally, some possible opportunities and challenges for further development of low-cost ceramic membrane are pointed out.     

浓海水处理及综合利用技术的新进展

对海水淡化过程产生的浓海水进行再脱盐,可进一步提高淡水回收率,并有效避免优质化学资源的浪费和对海洋生态环境的污染。本文介绍了多效蒸馏、共晶冷冻结晶、电渗析、膜蒸馏、膜结晶等浓海水再脱盐技术的原理、特点、应用实例和新进展,并对比分析了各种技术的优势和存在的不足,对基于多种热膜集成过程的浓海水“零排放”和综合利用技术进展作了重点讨论。最后指出,除相对成熟的多效蒸馏法和电渗析法外,其他多数浓海水再脱盐技术仍处于实验研究阶段,将反渗透与可再生能源驱动的膜蒸馏技术进行耦合发展高效盐化工将是浓海水处理领域的重要方向。     

陶瓷膜在水处理中的发展与应用

介绍了无机陶瓷膜的结构、原理及特性;综述了陶瓷分离膜技术的发展过程及其国内外发展现状;分类介绍了其在给水处理、海水淡化、废水处理等方面的应用研究及进展;最后讨论了陶瓷膜在水处理应用中存在的问题及发展趋势,指出其在水处理中具有良好的应用前景.     

多效膜蒸馏过程用于海水和浓海水的深度浓缩

研究了离子交换法选择性脱钙与多效膜蒸馏相结合用于海水淡化和淡化厂浓水深度浓缩的可行性。海水或浓海水中钙离子能脱除90%以上,可防止高倍数浓缩时海水中硫酸钙沉淀对膜造成污染。本文以膜通量、造水比和馏出液电导率为多效膜蒸馏过程的性能指标,研究了操作条件对过程性能的影响。膜通量最高可达6.07 L/(m2?h),造水比最高可达13.2;当海水浓缩至250 g/L时,馏出液的电导率小于200 μm/cm,膜通量和造水比仍可达3.61 L/(m2?h)和4.96。以除钙后的浓海水为料液,利用两种多效膜蒸馏组件分别进行了持续45天的操作稳定性实验研究,在试验期间膜组件性能没有明显下降。该研究结果表明,多效膜蒸馏结合选择性脱钙是适合于海水深度浓缩及资源综合利用的高效节能技术。     

亲疏水性CuBTC/PVDF复合膜应用于膜蒸馏抗油实验

采用水热法合成亲水性的CuBTC金属有机骨架(MOFs)颗粒，采用聚乙烯醇(PVA)作为黏合剂，用抽滤的方法将CuBTC颗粒附载在聚偏氟乙烯(PVDF)膜上，之后用戊二醛(GA)对PVA进行交联，制备出表层亲水、底层疏水的CuBTC/PVDF复合膜。通过场发射电子显微镜、比表面积及孔径分析仪、接触角测量仪、孔径分析仪、X射线衍射仪等对CuBTC颗粒和不同CuBTC含量的复合膜的表面特征、结构形态和稳定性进行了表征。结果表明，CuBTC颗粒有着较大的比表面积和孔容，CuBTC颗粒可以牢固地抽滤在PVDF膜表面，热稳定性高且有较好的柔韧性。与抽滤前的PVDF膜相比，随着CuBTC颗粒的增多，膜厚度有所增加，孔径和孔隙率有所减小，但对其膜蒸馏膜通量的影响不大，且在CuBTC含量在0.6 g时表现出较好的性能。在以1 g/L原油和35 g/L氯化钠混合溶液为进料液对原膜和复合膜进行直接接触膜蒸馏抗油污实验，发现原膜很快被油污染堵塞毛孔，而复合膜具有良好的抗油污染能力，可以进行长期的膜蒸馏实验。