膜反应器催化技术及膜催化材料的进展与展望

本文着重介绍近年来催化功能高分子膜和多孔金属或合金膜、多孔(金属)陶瓷复合膜、多孔玻璃复合膜、金属负载型复合膜与分子筛膜等选择性渗透无机膜材料的开发研究新进展及其在催化领域中的应用;列举几种典型的催化膜反应器的应用实例;指出膜反应器催化技术与膜材料的发展动向及应用前景;并对加强膜催化高技术领域的科学研究提出几点建议。     

生物功能催化膜定点固定化技术研究进展

介绍了从生物物理学、生物分析化学、化学工程学和分子生物学等学科角度研究开发的基于定点固定化技术的生物功能催化膜。着重阐述了基因定点突变技术、基因融合技术和翻译修饰技术等新兴定点固定化技术的原理、特点和操作。最后,对生物功能催化膜的研究方向进行了展望。     

丙烷脱氢制丙烯技术研究

介绍了催化脱氢、氧化脱氢、膜反应器脱氢等几种丙烷脱氢制丙烯技术，综述了丙烷催化脱氢制丙烯催化剂的研究现状，虽然丙烷催化脱氢生产丙烯已实现了工业化，但其催化剂的性能需进一步提高；对丙烷氧化脱氢制丙烯反应催化剂的研究现状及膜反应器在丙烷脱氢反应上所具有的优越性进行了描述，认为研发具有高稳定性和高透氢性能的氢分离膜，将有望能大幅度提高丙烯的收率。     

催化膜/过硫酸盐氧化技术研究进展

为解决过硫酸盐氧化技术中粉体催化剂的难回收问题及膜技术的局限性，将膜技术与过硫酸盐氧化技术结合降解水体污染物受到广泛关注。介绍了催化膜在过硫酸盐氧化体系的反应机理，系统地综述了催化膜的制备方法在过硫酸盐氧化体系的应用。通过对催化膜的制备过程和性能进行比较，总结了不同制备方法的优缺点及催化膜与其他高级氧化技术的综合利用。简要阐述了当前技术存在的问题与挑战，并展望了未来的研究方向。     

分子筛膜的合成与应用研究进展

介绍了分子筛膜的合成方法,如水热合成法、二次生长法、连续流合成法、微波辅助合成法、杂原子掺杂法、混合基质法等,阐述了分子筛膜在分离和催化中的应用,并对分子筛膜的发展方向进行了展望,认为加强分子筛膜的成膜机理和改性研究,并深入开发分子筛膜在催化及分离中的应用,制备出具有工业应用价值的分子筛膜.     

无机膜催化氧化在环境工程中的进展与应用

介绍了无机膜催化氧化在空气污染控制中的应用;对无机膜材料的种类及制备进行了比较,同时介绍了膜催化技术中催化剂的制备及无机催化膜的应用,以及纳米催化膜的进展,并对无机膜催化氧化在环境工程中的应用进行了展望。     

PEMFC膜电极组成及其性能

质子交换膜燃料电池(PEMFC)的膜电极(MEA)由质子交换膜、催化层、水管理层(WML)和扩散层组成。研究了WML的厚度和聚四氟乙烯(PTFE)的含量对膜电极性能的影响,并采用了两种新型造孔剂(碳酸氢铵和硫酸铵)优化WML的孔结构。采用环境扫描电镜(ESEM)表征了膜电极的表面形貌和孔结构;采用单体PEMFC的电流密度-电压曲线评价了膜电极在外增湿和自增湿方式下的极化特性,结果表明,WML的建立提高了膜电极的水管理能力,使膜电极在自增湿方式下具有良好的极化特性。     

膜分离-电催化氧化耦合处理高含量苯酚废水的研究

采用溶胶凝胶法制备TiO2溶胶,以管式炭膜(TCM)作为基体,通过浸渍法在TCM表面涂覆TiO2催化层,炭化后得到具有催化性能的TCM;将得到的管式催化炭膜作为阳极应用于自制膜反应器,将膜分离和电催化技术耦合处理高含量苯酚废水。X射线衍射(XRD)结果表明TCM表面TiO2属于锐钛矿型,具有较高的催化活性;循环伏安法(CV)表明TCM催化电极对苯酚有明显的催化氧化作用;膜分离-电催化耦合技术相比单纯电催化对苯酚有更好的降解效果,在相同处理时间内可提高约40%的去除率,是一种可行的集成技术。并探讨了膜反应器的优化运行参数。     

LB膜研究的当前状况和应用前景

“分子工程”这门新兴学科的内容是按预定目标设计和组装具有特殊功能的高度有序的分子组合体——“超分子机器”(Supramolecular machines)。分子组装的各种技术中,最早发明并且至今仍然用得最广泛的是Langmuir-Blodgett薄膜(LB膜)技术。这种技术是先在液-气界面形成紧密排列的单分子层(monolayer),然后将单层逐层地转移到固体上,形成LB累积层膜(multilayers)。 LB膜的研究跟分子生物学、分子组合化学和微电子学等学科的发展紧密联系。目前,各国对     

工业废水膜浓缩液的高级氧化技术综述

当前，我国经济快速发展，工业废水排放量也在快速增长，工业废水中往往含有多种有毒、有害物质。通过膜技术处理工业废水是目前比较常用的方法，但膜处理技术在处理过程中会产生大量毒性较强、可生化性较差、有机质浓度较高、含盐量较高的膜浓缩液，因此，如何妥善处理危害性更大的膜浓缩液已经成为当前研究的热点。本文介绍了臭氧工艺、芬顿工艺、紫外催化湿式氧化工艺等常用的高级氧化技术(AOPS)以及膜浓缩液处理已有成果。目前单一技术处理效果有限，一般均采用多项技术结合处理膜浓缩液，如紫外催化湿式氧化工艺与高效脱氮菌结合。     

MFI型沸石膜的渗透分离性能及应用

综述了ＭＦＩ型沸石分子筛的渗透分离性能，探讨了其可能的分离机理，并介绍了包括膜分离与经在内的前沿进展。     

Advanced functional polymer membranes

This feature article provides a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane separation processes for liquid and gaseous mixtures (gas separation, reverse osmosis, pervaporation, nanofiltration, ultrafiltration, microfiltration) and in other important applications of membranes such as biomaterials, catalysis (including fuel cell systems) or lab-on-chip technologies. Important approaches toward this aim include novel processing technologies of polymers for membranes, the synthesis of novel polymers with well-defined structure as ‘designed’ membrane materials, advanced surface functionalizations of membranes, the use of templates for creating ‘tailored’ barrier or surface structures for membranes and the preparation of composite membranes for the synergistic combination of different functions by different (mainly polymeric) materials. Self-assembly of macromolecular structures is one important concept in all of the routes outlined above. These rather diverse approaches are systematically organized and explained by using many examples from the literature and with a particular emphasis on the research of the author's group(s). The structures and functions of these advanced polymer membranes are evaluated with respect to improved or novel performance, and the potential implications of those developments for the future of membrane technology are discussed.     

Recent developments on catalytic membrane for gas cleaning

Catalytic membrane, a novel membrane separation technology that combines catalysis and separation, exhibits significant potential in gas purification such as formaldehyde, toluene and nitrogen oxides(NO_x). The catalytic membrane can remove solid particles through membrane separation and degrade gaseous pollutants to clean gas via a catalytic reaction to achieve green emissions. In this review, we discussed the recent developments of catalytic membranes from two aspects: preparation of catalytic membrane and its application in gas cleaning.Catalytic membranes are divided into organic catalytic membranes and inorganic catalytic membranes depending on the substrate materials. The organic catalytic membranes which are used for low temperature operation(less than 300 °C) are prepared by modifying the polymers or doping catalytic components into the polymers through coating, grafting, or in situ growth of catalysts on polymeric membrane. Inorganic catalytic membranes are used at higher temperature(higher than 500 °C). The catalyst and inorganic membrane can be integrated through conventional deposition methods, such as chemical(physical) vapor deposition and wet chemical deposition. The application progress of catalytic membrane is focused on purifying indoor air and industrial exhaust to remove formaldehyde, toluene, NO_x and PM2.5, which are also summarized. Perspectives on the future developments of the catalytic membranes are provided in terms of material manufacturing and process optimization.     

Recent progress in fluoropolymers for membranes

Fluoropolymers usually have high mechanical strength and excellent chemical stability and thus have been employed for the last several decades as materials for membrane separation processes, typically in water purification and energy applications such as microfiltration (MF), ultrafiltration (UF), fuel cells, battery separators, etc. Recently, new membrane operations such as membrane distillation (MD), membrane crystallization (MCr), membrane emulsification (ME) and membrane contactors (MC) have become popular. A much stronger understanding of the basic properties of the materials utilized is required for adopting the appropriate membrane and for finding the relationship among material properties, membrane morphology and the transport phenomena in the membranes. This review presents the structures and properties of fluoropolymers for membranes, the preparation and modification methods of fluoropolymer membranes, and their applications. Recent progress in the development of novel fluoropolymers for membranes and their fabrication and modification methods are reported as well.     

Ozone Cleaning of Fouled Poly(Vinylidene) Fluoride/Carbon Nanotube Membranes

This research demonstrates for the first time that ozone is an effective cleaning agent for polyvinylidene fluoride (PVDF) membranes fouled by natural organic matter (NOM). Bare PVDF membranes as well as PVDF impregnated with CNTs (pristine (CNTs–P) and oxidized (CNTs–O)) at 0.3% mass membranes were used. Three different methods were investigated for cleaning the fouled membranes including; A: 10-min cleaning by pure water, B: 5-min water followed by 5-min ozonated water, and C: 10-min fully ozonated water. It was found that the application of fully ozonated water for 10 min was very effective to reinstate the flux to almost its original value of unfouled membrane. The CNTs–P/PVDF membrane exhibited the highest fouling with a total fouling ratio of 81%, while for the bare PVDF and the CNTs–O/PVDF membranes, the fouling ratios were 76% and 74%, respectively. The full ozonated water cleaning method gave the highest removal of fouling leaving the lowest irreversible fouling on the membrane as compared to the other cleaning methods. On the other hand, the highest removal of NOM fouling was obtained for CNTs–O/PVDF membranes indicating that fouling on CNTs–O/PVDF membrane was less bound than the other membranes. Contact angle measurements of the fouled membranes showed that all membranes exhibited increased contact angles due to the NOM deposition but after cleaning, particularly with ozonated water, the membrane contact angles returned to almost their original values. FTIR analysis of the membranes corroborated the results obtained.     

Development of ultrafiltration membranes from acrylonitrile co-polymers

Summary Hydrophobic polymer surfaces show higher tendency to protein adsorption and bacteria attachment, thus hydrophobic polymeric membranes foul rapidly in water purification operations. A change in membrane surface properties can reduce fouling; this may be accomplished by increasing the hydrophilicity of the membrane surface, and by using a membrane with smaller pore size. The ultrafiltration membranes were prepared via phase inversion process in our laboratory. Negatively charged hydrophilic ultrafiltration membranes were prepared from acrylonitrile-vinyl acetate (CP16)/Acrylonitrile-vinyl acetate-sodium p-sulfophenyl methallyl ether (CP24). Scanning electron microscopy (SEM) revealed the asymmetric structure of these membranes. The roughness of the surface was measured by atomic force microscopy (AFM). The basic characteristics of these membranes like water permeability, water content and membrane selectivity were also measured. Received: 29 April 2001/Revised version: 14 September 2001/Accepted: 14 September 2001     

Recent advances in nanofiltration,reverse osmosis membranes and their applications in biomedical separation field

In the face of human society's great requirements for health industry, and the much stricter safety and quality standards in the biomedical industry, the demand for advanced membrane separation technologies continues to rapidly grow in the world. Nanofiltration (NF) and reverse osmosis (RO) as the high-efficient, low energy consumption, and environmental friendly membrane separation techniques, show great promise in the application of biomedical separation field. The chemical compositions, microstructures and surface properties of NF/RO membranes determine the separation accuracy, efficiency and operation cost in their applications. Accordingly, recent studies have focused on tuning the structures and tailoring the performance of NF/RO membranes via the design and synthesis of various advanced membrane materials, and exploring universal and convenient membrane preparation strategies, with the objective of promoting the better and faster development of NF/RO membrane separation technology in the biomedical separation field. This paper reviews the recent studies on the NF/RO membranes constructed with various materials, including the polymeric materials, different dimensional inorganic/organic nanomaterials, porous polymeric materials and metal coordination polymers, etc. Moreover, the influence of membrane chemical compositions, interior microstructures, and surface characteristics on the separation performance of NF/RO membranes, are comprehensively discussed. Subsequently, the applications of NF/RO membranes in biomedical separation field are systematically reported. Finally, the perspective for future challenges of NF/RO membrane separation techniques in this field is discussed.     

Sulfonated Polyethersulfone (SPES) – Charged Surface Modifying Macromolecules (cSMMs) Blends as a Cation Selective Membrane for Fuel Cells

Polyethersulfone (PES) was sulfonated by chlorosulfonic acid and concentrated sulfuric acid. The pure sulfonated PES (SPES) and modified SPES membranes were prepared by blending with different charged surface modifying macromolecules (cSMMs) namely, SPES/DEG‐HBS, SPES/PEG‐HBS, and SPES/PPG‐HBS. Membranes were characterized for their morphology, physical properties, and electrochemical properties in order to evaluate these membranes as cation exchange membranes. The blended membranes showed an increase in hydrophilicity, water uptake, and proton conductivity compared to the pure SPES membranes. The highest values of water uptake and proton conductivity were obtained for the SPES/PPG‐HBS blended membrane. Morphological studies revealed that the nodule size and surface roughness also influenced the water uptake, apart from the additional –SO₃H group. Among the modified membranes, the SPES/DEG‐HBS blended membrane exhibited a lower methanol permeability value of 8.895 × 10⁻⁸ cm² s⁻¹ than the corresponding SPES membrane. The other two cSMM blended membranes showed higher methanol permeability values than SPES but still a smaller value than Nafion 117. The highest selectivity ratio (i.e., ratio of proton conductivity to methanol permeability) was obtained with the SPES/DEG‐HBS cSMM blended membrane. These results showed that the SPES/cSMM blended membranes have promise for possible use as a cation exchange membrane in fuel cells and electrolyzer applications.     

Performance of ceramic composite membrane for the separation of VOCs

Zeolite composite membranes were prepared for the separation of VOCs by the pressurized coating method. On the top of the composite membrane, TiO₂, polyimide or polyethersulfone were coated by the same tech-100 nm-sized nique.ZSM-5 coated membranes show higher selectivity for n-hexane in n-hexane/benzene mixture than 500 nm sized ZSM-5 coated membrane. Composite membrane coated with 100 nm zeolite and polymer showed the highest selectivity (44) for n-hexane/benzene.     

Electrochemical characterization and assessment of performance of zirconium phosphate and zinc modified zirconium phosphate membranes in aqueous sodium chloride solutions

Prepared membranes, zinc-zirconium phosphate (M-1 and M-2) and zirconium phosphate (M-3) were electrochemically characterized by membrane potential and membrane conductance measurements using aqueous sodium chloride solution of varying compositions. The data have been used for the estimation of transport number of ions and solvent in the membrane phase in addition to permselectivity and membrane fixed charge density. Membrane conductance data were used to estimate the ionic permeability and verify diffusion controlled criteria endowed with the membrane phase. Solute and co-ion permeabilities were compared and found that their values were comparable. Solute rejection of membranes was examined for limiting and intermediate cases of solute–solvent interaction in the membrane phase along with positional solute rejection. Zirconium phosphate membrane showed considerable polarization index deviation from unity indicates its minor perspective than zinc-zirconium phosphate membrane. Results show that zinc modified zirconium phosphate membranes reflected modified elastic properties than zirconium phosphate membrane. The well-known Teorell–Meyer–Sievers (TMS) theory, which describes the membrane potential for charged membranes, was considered as a frame work.