Water vapor permeation and compressed air dehydration performances of modified polyimide membrane

In this paper, modification of polyimide hollow fiber membrane was carried out by introduction of tetrabutylammonium naphthalenesulfonate (BAN) into the membrane matrix. Permeation performance of modified hollow fibers was investigated helps to compressed air dehydration ability across the membrane. The experimental results showed that water sorption and water vapor permeability obviously increase with increase on BAN content in modified membranes, and air dehydration performance was improved by increasing BAN in membrane and ratio of sweeping gas. Moreover, operational pressure and feed flux also impose on important effect on compressed air dehydration capability.     

Numerical simulation studies on heat and mass transfer using vacuum membrane distillation

A general 2D mathematical model was developed to simulate the purification of water from volatile organic compounds (VOCs) via vacuum membrane distillation (VMD) process in hollow fiber membrane contactors. The model was developed for hydrophobic membrane material conditions, taking into consideration axial and radial diffusion in the tube, membrane and compartments of the contactor and was simplified to the two‐dimensional structure with a single porous membrane wall. The simulation has studied the mass and heat transfer of VMD system in the porous media, in which aqueous volatile organic solution was considered as an incompressible and steady fluid. Effect of the downstream pressure on the removal of 1, 1, 1‐trichloroethane (TCA) was studied to validation of simulation results with experimental data that it was obtained from literature. The temperature, Reynolds number, and total mass flux (convective and diffusive) distribution of TCA are determined in the membrane module. POLYM. ENG. SCI., 54:2553–2559, 2014. © 2013 Society of Plastics Engineers     

陶瓷膜净水技术试验研究

试验利用无机陶瓷膜的截留作用来处理南方某水厂的待滤水,研究了陶瓷膜净水的主要影响因素及变化规律,提出了用陶瓷膜净水工艺替代传统的过滤工艺的水处理系统。考查了不同操作条件对膜通量的影响、陶瓷膜对浊度的去除以及陶瓷膜工艺对水中的溶解性有机污染物的去除效果。试验表明陶瓷膜具有良好的过滤性能。     

纳米纤维膜在空气净化中的应用研究进展

面向空气净化的应用需要,开发高效净化材料已成为研究热点之一,其中具有相互连贯孔结构的纳米纤维膜在高效空气净化领域展示出巨大的应用前景。对于纳米纤维膜对空气净化效果的评估指标通常包括过滤效率和过滤阻力。本文介绍了串珠、蛛网和复合等结构纳米纤维膜的研究进展,分析了驻极式纳米纤维膜在高效除尘方面的应用现状,探讨了银纳米颗粒和半导体金属氧化物改性纳米纤维膜在抗菌和除有机易挥发性气体等多功能性空气净化中的应用可行性,指出了高效低阻、功能化是纳米纤维膜用于空气净化领域的研究重点。并提出今后应高度关注多污染物对纳米纤维空气净化膜性能的影响,深入研究具有多功能协同作用的纳米纤维空气净化膜,以期获得更广泛的应用。     

Removal of natural organic matter in water using functionalised carbon nanotube buckypaper

A simple, surfactant-free assembly process was used to prepare multi-wall carbon nanotube (CNT) buckypapers using a highly efficient purification, sonication, and filtration process. To achieve effective dispersion of CNT into ethanol, a minimum 5-min sonication time was required. Here, we fabricated a buckypaper with pore size of 41 ± 10 nm and porosity of 72.9% with a 10-min sonication. The as-prepared buckypaper was used as a membrane for humic acid (HA) removal from water. During purification process, carboxylic and hydroxylic functional groups were introduced onto the CNT surface. The functional groups increased the hydrophilicity of the CNTs and improved the removal efficiency of HA by the buckypaper. The buckypaper prepared from purified CNTs exhibited excellent removal of HA (>93%) and a long lifetime for filtration.     

膜分离技术处理航天废水

采用膜分离技术对航天废水进行深度净化,整机净化流程为多段梯度过滤,预处理为微米级砂滤及臭氧曝气,经氧化沉淀后的水再经过超滤（UF）处理,此时的出水已可回用于一般冲洗用途;随后,在反渗透（RO）装置中将UF系统的出水再进行深度净化,水质中化学需氧量（COD）、氨氮和偏二甲基肼浓度分别为：< 10mg/L、4.4mg/L和<0.5mg/L,可回用于较高用途。废水深度净化后,污染物被吸附于膜表面,RO膜出现压差不断增加、产水量减少、产水电导略微上升的现象。膜清洗选用0.8mol/L的NaOH和0.5%的84消毒液的混合液作为清洗剂,浸泡28h后清洗效果最佳。实验结果表明膜分离深度净化航天废水工艺的技术可行,经济效益可观,绿色环保,实现了循环经济,可降低航天废水对环境的污染。     

Biofuel purification in GME zeolitic–imidazolate frameworks: From ab initio calculations to molecular simulations

A multiscale modeling study is reported on the adsorption of ethanol/water in five zeolitic–imidazolate frameworks (ZIFs) for biofuel purification. The ZIFs (ZIF‐68, ?69, ?78, ?79, and ?81) have isoreticular Gmelinite topology but differ in organic linkers. The simulated adsorption isotherms of ethanol and water in ZIF‐68 agree fairly well with experimental data. At a low pressure, ZIF‐78 exhibits the highest uptake due to strong hydrogen‐bonding between ?NO₂ groups and adsorbates. The heats of adsorption at infinite dilution largely follow the trend of binding energies estimated from ab initio calculations. At a high pressure, the uptake is governed primarily by free volume but also affected by hydrogen‐bonding. Among the five ZIFs, ZIF‐79 with hydrophobic ?CH₃ groups shows the highest adsorptive selectivity for ethanol/water mixtures. This study provides microscopic insights into the adsorption and separation of ethanol/water in ZIFs, and would facilitate the development of new ZIFs for biofuel purification. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2763–2775, 2015     

麦芽糖醇纳滤浓缩过程中膜的污染和清洗再生

采用纳滤方法对麦芽糖醇进行提纯和浓缩,可以节约大量的能耗。文中系统研究了该纳滤过程中操作条件对膜污染的影响,并对膜的清洗和再生效果进行了考察。实验结果表明,膜的污染程度随操作压差和原料液质量分数的增大而加剧,随循环流量和操作温度的升高而减轻。另外,采用常压、循环流量为100—120 L/h,40℃左右的去离子水冲洗30 m in,可达到满意的效果,再将被污染的膜浸泡36 h,基本能使膜纯水通量恢复到使用前的状态。     

室内空气中三氯乙烯在TiO_2/AC上的光催化氧化反应动力学

采用具有多层结构的蜂窝状整体式光催化净化块为催化材料 ,设计了室内空气净化光催化反应器 ,以三氯乙烯 (TCE)为模拟污染物 ,在 2 5℃、常压下 ,进行水、TCE的吸附等温线的测试和 TCE的光催化降解反应动力学研究。水与 TCE的平衡吸附采用 L angmuir吸附等温线表示 ;TCE在 Ti O2 表面的光催化反应采用简单的 L- H速率方程来表征 ;并进行了模型值与实验值的比较 ,结果令人满意     

Separation of liquid mixtures by using polymer membranes. I. Water–alcohol separation by pervaporation through PVA-g-MMA/MA membrane

A membrane was designed for the separation of a water–alcohol mixture by pervaporation on the basis of the difference in hydrogen-bonding interaction between two components of the membrane. Two kinds of poly(vinyl alcohol)-g-maleic anhydride/methyl methacrylate membrane were prepared by different methods: (1) A homogeneous membrane was formed by casting from dimethyl sulfoxide solution after purification. (2) A porous membrane was obtained directly by casting from the reaction solution, and then was purified. It is found that water was permeated through a homogeneous membrane preferentially in all ranges of feed compositions. Moreover, the flux was found to decrease with increasing PVA content in the membrane. The porous membrane after heat treatment has selective permeability for methanol. Pervaporation of water was investigated with respect to the feed concentration and also to the operating conditions. The effect of the molecular size of the permeating species on both permeation and separation is also discussed.     

Enhanced antipressure ability through graphene oxide membrane by intercalating g-C3N4 nanosheets for water purification

Graphene oxide (GO) membranes have shown great potential for water purification, but their permeability and antipressure ability are poor, which limits their practical applications. In this study, two-dimensional graphitic carbon nitride (g-C₃N₄) nanosheet-intercalated GO (GOCN) membranes were developed to improve the separation performance of GO membranes, especially under high operating pressure. After incorporation of the g-C₃N₄ nanosheets, the amount of permeable nanochannels (wrinkles or corrugation) in the membrane increased; hence, the water permeance was effectively improved (twice as high as that of GO membranes). Moreover, the antipressure performance of the GOCN membranes was significantly enhanced (even below 0.5 MPa pressure) as the nanochannels in the composite membranes become stable and rigid due to the support of the pressure-resistant g-C₃N₄ nanosheets. The good separation performance demonstrates that the intercalation of g-C₃N₄ is an effective strategy to improve the GO-based membrane properties, which can promote their application in water purification.     

Generation of Coarse Bubbles and Flow Instability Control by Means of a Bubble Generator

A previously studied bubble generator was tested under new operating conditions to provide for millimeter‐sized bubbles. The basic element of the generator is a vortex chamber with water supplied through tangential ducts while gas (air) is introduced in the radial direction. Bubbles with average diameter of 0.5–2.2 mm were produced and registered by high‐speed photography. The correlation between the water‐air flow rate ratio and the characteristic bubble diameter was established and described by a relationship. Pressure oscillations in the exit section of the device were captured for two‐phase flows with fine and coarse bubbles. With a view to applications in membrane filtration and water treatment, the effect of a pin installed in the exit section of the vortex chamber on the pressure oscillations was studied. The pin results in a drastic increase in pressure amplitude, both in the flow without bubbles and in the case of gas supply.     

Bench-Scale Aerosol Filtration Test System and Evaluation of an Acoustic Bioaerosol Removal Device for Indoor Air Streams

It is important to have well-defined, reproducible methods to evaluate and compare newly developed air filtration equipment. To facilitate accurate assessment of air purification devices at the bench scale, an experimental system was designed, built, and documented to evaluate particulate removal efficiency (PRE) of air filtration devices based on principles used in ASHRAE standards. The system was then carefully characterized and used to evaluate PRE and total energy consumption of a novel acoustically enhanced impaction (AEI) air purification device. The AEI device demonstrated 99.998% PRE of 0.5–1.5 μm diameter KCl particles while causing a 120 Pa pressure drop and requiring a total of 3.0 W/l of air treated at indoor ambient conditions. A single element of the AEI device operated in a biological safety level 2 facility was then used to evaluate PRE of bioaerosol consisting of Bacillus cereus (BC) spores. PRE of BC was 99.86 ± 0.05% at indoor ambient temperature and pressure. This research describes the use of the Bench-scale Air Purification Testing and Evaluation Chamber (BAP-TEC) to experimentally evaluate and compare PRE and total energy requirements of novel air purification devices at the bench scale (280–1400 alpm). Further, an AEI device containing a fibrous filter media and high intensity sound field in the same control volume is evaluated using the BAP-TEC. Temporally resolved PRE of a bioaerosol by the AEI is also presented.

Copyright 2013 American Association for Aerosol Research     

A thermodynamic benchmark for assessing an emergency drinking water device based on forward osmosis

Following the creation of the first reverse osmosis (RO) membrane in the 1960s, the technique has been widely used for the purposes of both small scale and municipal seawater desalination. Forward osmosis (FO) is now also emerging as a possible contender, with the potential for much lower energy consumption. In this study, we have developed a thermodynamic benchmark for use in assessing the suitability of a potable water system for purifying small amounts of brackish water in emergency situations. The light, portable and re-usable purification system is driven by FO. A pouch is filled with draw solution and immersed in brackish water; the pouch incorporates a traditional RO membrane. The ‘draw solution’ contains digestible salts and/or sugars to provide an osmotic pressure difference across the membrane, thus drawing in purified water across the membrane. Three such draw solutions were produced and tested, allowing the osmotic potential of the solution to be determined over a succession of dilutions. The results could be fitted with a power law function. In order to take account of the solution non-ideality and the non-linearity of flux rates, a thermodynamic relationship was used in conjunction with a membrane transport model to develop a benchmark which describes the ideal behaviour of a FO water system. This benchmark, in conjunction with the power law function, showed that such a system could be used in an emergency to provide safe, potable water in a reasonable time interval and without the need for a power source. The study has also suggested the possibility of a continuous water purification system based upon this principle, and has drawn attention to the benefits of novel draw solutes in such a system.     

Review on structural control and modification of graphene oxide-based membranes in water treatment: From separation performance to robust operation

Membrane separation has become an important technology to deal with the global water crisis. The polymerbased membrane technology is currently in the forefront of water purification and desalination but is plagued with some bottlenecks. Laminated graphene oxide(GO) membranes exhibit excellent advantages in water purification and desalination due to the single atomic layer structure, hydrophilic property, rich oxygen-containing groups for modification, mechanical and chemical robust, anti-fouling properties, facile and large-scale production, etc. Thus the GO-based membrane technology is believed to offer huge opportunities for efficient and practical water treatment. This review systematically summarizes the current progress on the water flux and selectivity intensification, stability improvement, anti-fouling and anti-biofouling ability enhancement by structural control and modification. To improve the performance of the laminated GO membrane, interlayer spacing tunability and surface modification are mainly used to enhance its water flux and selectivity. It is found that the stability and biofouling also block the service life of the GO membrane. The crosslinking method is found to effectively solve the stability of GO membrane in aqueous environment. Introducing nanoparticles is a widely used method to improve the membrane biofouling ability. Overall, we believe that this review could provide benefit to researchers in the area of GO-based membrane technology for water treatment.     

Preparation of antifouling ultrafiltration membranes from copolymers of polysulfone and zwitterionic poly(arylene ether sulfone)s

The past few decades have witnessed rapid gains in our demands of antifouling membranes such as water purification membranes and hemodialysis membranes. A variety of methodologies have been proposed for improving the antifouling performance and the hemocompatibility of the membranes. In this study, a series of copolymers (PSF-PESSB) containing polysulfone (PSF) and poly(arylene ether sulfone) bearing pendant zwitterionic sulfobetaine groups (PESSB) were prepared via one-pot polycondensation. Subsequently, the ultrafiltration (UF) membranes were prepared from different zwitterion-containing copolymers. The prepared membranes showed high thermal stability and mechanical properties. Besides, it also displayed attractive antifouling performance and blood compatibility. Compared with the original PSF membrane, the amount of protein absorption on the modified membrane was reduced; the flux recovery ratio and the resistance to blood cells were significantly improved. The results of this work suggest that PSF-PESSB membranes are expected to be applied in blood purification. The introduction of zwitterion-containing polymers to membranes paves ways for developing advanced hemodialysis technologies for crucial process.     

Pure hydrogen generation in a fluidized-bed membrane reactor: Experimental findings

A pilot-scale fluidized-bed membrane reactor was tested for the production of hydrogen. The prototype reactor operated under steam methane reforming (SMR) and autothermal reforming (ATR) conditions, without membranes and with membranes of different total areas. Heat was added either externally or via direct air addition. Hydrogen permeate purity of up to 99.995+% as well as a pure-H₂-to-natural-gas yield of 2.07 were achieved with only half of the full complement of membrane panels active under SMR conditions. A permeate-H₂-to reactor natural gas feed molar ratio >3 was achieved when all of the membrane panels were installed under SMR conditions. Experimental tests investigated the influence of such parameters as reactor pressure, hydrogen permeate pressure (vacuum vs atmospheric pressure), air top/bottom split, feed flowrate and membrane area. Reactor performance was strongly dependent on the active membrane surface area.     

Preparation of a modified crosslinked chitosan/polyvinyl alcohol blended affinity membrane for purification of His-tagged protein

Based on a crosslinked chitosan (CS)/polyvinyl alcohol (PVA) matrix membrane, an immobilized metal ion affinity membrane (IMAM) using Cu²⁺ and Ni²⁺ ions as affinity ligands was prepared for purification of the His-tagged recombinant protein. The affinity membrane possessed a favorable membrane structure including 1.39 μm average pore size and 0.33 mL·cm⁻²·s⁻¹ water flux under 0.08 MPa pressure at 25 °C. The Cu²⁺ and Ni²⁺ ions capacities immobilized on the IMAM were 155.6 and 137.3 μmol·disk⁻¹, respectively. The IMAM had an excellent specific affinity to His-tagged protein. About 10-fold purification factor for the model protein was obtained in a batch adsorption, and serine hydroxymethyl transferase could be purified to a single band in sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis from its crude extract solution with an affinity membrane cartridge by a dynamic purification process. This work provides a promising IMAM for the purification of His-tagged recombinant proteins. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47347.     

膜气提法去除水体中甲基叔丁基醚的实验研究

对采用聚丙烯中空纤维膜组件运用膜气提法去除水体中甲基叔丁基醚(MTBE)进行了初步研究,着重考 察了温度、气体流速、液体流速及气体压力等因素对去除效果的影响.结果表明,膜气提法是一种比较有效地去除水中MTBE的技术,去除率98%左右;温度、气体流速和液体流速对去除率有显著影响:去除率随水温的升高而增大,随气体流速和液体流速的增加而升高;而气体压力对去除率的影响则不明显.