Plasma modification of aromatic polyamide reverse osmosis composite membrane surface

The surface of aromatic polyamide reverse osmosis composite membrane was modified by oxygen and argon plasma. The water permeability of oxygen-plasma-modified membrane increases, and the chlorine resistance of argon-plasma-modified membrane increases. The spectra of the attenuated total reflection-Fourier transform infrared and X-ray photoelectron spectroscopy and the contact angle of the water were analyzed to explain the improvement of the two performances of the composite membrane. The carboxyl groups were introduced when modified by oxygen plasma, and cross-linking occurred when modified by argon plasma. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1923–1926, 1997     

Effect of surface properties of polysulfone support on the performance of thin film composite polyamide reverse osmosis membranes

In this work, influence of initial conditions and surface characteristics of porous support layer on structure and performance of a thin film composite (TFC) polyamide reverse osmosis (RO) membrane was investigated. The phase inversion method was used for casting of polysulfone (PSf) supports and interfacial polymerization was used for coating of polyamide layer over the substrates. The effect of PSf concentrations that varied between 16 wt % and 21 wt %, and kind of the solvent (DMF and NMP) used for preparation of initial casting solution were investigated on the properties of the final RO membranes. SEM imaging, surface porosity, mean pore radius, and pure water flux analysis were applied for characterization of the supports. The substrate of the membrane, which synthesized with 18 wt % of PSf showed the most porosity and the synthesized RO membrane had the lowest salt rejection. In case of the solvents, the membranes synthesized with DMF presented better separation performance that can be attributed to their lower thickness and sponge‐like structure. The best composition of support for TFC RO membranes reached 16 wt % PSf in DMF solvent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44444.     

Chlorine-resistance of reverse osmosis (RO) polyamide membranes

Polyamide (PA) reverse osmosis (RO) membranes suffer performance decay when exposed to oxidizing species, limiting their lifetime and increasing operation costs. This article aims at reviewing the effect of chlorine species on the performance and characteristics of PA-membranes. Experimental evidence supporting different competing mechanisms for chlorine-polymer interaction will be presented, together with the influence of operational parameters. Additionally, an overview of different modification methods that exist to render PA-membranes more chlorine-resistant is given.     

介质阻挡放电等离子体处理芳纶的表面性能研究

采用介质阻挡放电(DBD)装置对芳纶1414表面进行改性处理,探讨低温等离子体处理对纤维表面性能的影响。结果表明:经过DBD等离子体处理后,芳纶1414纤维表面粗糙程度加剧,粘结性能和浸润性能有了明显的改善;当DBD等离子体处理功率为200～300 W,时间为60 s,氩气流量为2～3 L/min时,芳纶1414的界面剪切强度从处理前的11.9 MPa上升到14.2 MPa,接触角由处理前的85.0°下降到了60.6°。     

Some transport characteristics of aromatic polyamide membranes in reverse osmosis

The effects of solute concentration in the range of 0.0013 to 1.051 molality in the feed solution and operating pressure in the range of 100 to 900 psig on solute transport parameter D_AM/Kδ in reverse osmosis have been studied for a class of laboratory-made aromatic polyamide membranes and aqueous sodium chloride feed solutions. The results showed that D_AM/Kδ for NaCl increased both with increase in operating pressure and solute concentration in the concentrated boundary solution on the high-pressure side of the membrane. A general expression for D_AM/Kδ for NaCl including the effects of both the above operating variables is given. These results are different from the corresponding results obtained for cellulose acetate membranes.     

Long-lasting ceramic composites for surface dielectric barrier discharge plasma actuators

The developed research presents a novel experimental study of the cost-effective MgO-Al₂O₃, MgO-CaZrO₃ perovskite, and thermally stable YSZ ceramic composites for DBD plasma actuators in aerospace applications. This study focuses on the implementation of ceramic DBD plasma actuators for aerodynamic flow control and ice creation mitigation. For this purpose, electrical power consumption analysis, induced flow velocities assessment, and mechanical and thermal characterization were performed. MgO-Al₂O₃ presented higher induced velocities than its zirconia-based counterparts of up to 3.3 m/s, and lower heat dissipation, achieving a ceiling temperature of 46 ºC, being thereby the best-suited candidate for active flow control mechanisms. In contrast, YSZ had very high-power consumption translated into a maximum surface temperature of 155.4 ºC, establishing itself for ice mitigation. This extensive research evinces that the strategic combination of the developed ceramics' thermomechanical, thermoelectric, and electromechanical properties allows them to be a promising breakthrough material for DBD plasma actuators.     

介质阻挡放电等离子体改性碳基材料研究进展

介质阻挡放电等离子体因其高效、经济和易操作等优点, 使得其在材料表面改性方面得到了广泛的应用, 同时表现出良好的应用前景。碳基材料由于其许多良好的物化性能, 使得其在很多领域都得到了很好的应用。而经DBD改性后的碳基材料表现出更好的物化性能, 应用更加广泛。主要综述了DBD在改性碳基材料方面的研究现状, 包括活性基团的引入, DBD改性对碳基材料界面结合能、吸附性能、物理结构及其对负载组分分散度的影响。指出改性过程中仍然存在的许多不够完善之处, 提出许多需要进一步深入研究的问题, 如DBD改性对碳基材料物化性能影响的机理研究, 并展望了DBD改性碳基材料技术未来的发展前景。     

介质阻挡放电在芳纶表面改性中的应用

综述了介质阻挡放电应用于芳纶表面改性研究的最新进展;介绍了介质阻挡放电的机理、特点以及国内主要的介质阻挡放电等离子体的设备;阐述了介质阻挡放电对芳纶亲水性能和粘结性能等表面性能的改善。指出芳纶等离子体表面改性的时间效应限制了其广泛应用,应进一步加强纤维表面等离子体改性的机理研究。     

Catalysis assisted plasma decomposition of benzene using dielectric barrier discharge

Atmospheric non‐thermal plasma generated by dielectric barrier discharge was applied to decompose benzene with a sheet type catalyst of platinum supported by alumina. The experimental results indicated that an enhancement of the decomposition by the catalyst was achieved at low concentration of benzene. Ozone produced in the plasma seemed not to contribute to the decomposition. The deactivation of the catalyst was also observed due to decomposition products such as CO and a solid deposit. However a heating treatment could regenerate the catalyst. The results suggested the plasma‐catalyst hybrid reactor was the effective method to solve volatile organic compound (VOCs) problem.     

介质阻挡放电等离子体反应器降解盐酸四环素

采用介质阻挡放电等离子体反应器降解盐酸四环素（TC）,研究了输入功率、放电间距、气体流量、初始浓度等参数对盐酸四环素降解效果的影响,结果表明当输入功率为1.3 W,放电间距为2.5 mm,气体流量为150 ml·min^-1,初始浓度为100 mg·L^-1时降解效果最好,放电处理30 min盐酸四环素的降解率达到92%。动力学研究表明盐酸四环素的降解过程符合拟二级动力学方程。检测了降解过程中生成的中间产物,提出了盐酸四环素的降解路径与机理。     

介质阻挡放电技术处理挥发性有机物的研究进展

介质阻挡放电技术在处理低浓度挥发性有机物（VOCs）过程中具有反应快速、工艺简单及适应范围广等优点而受到广泛关注。本文从介质阻挡放电单独使用和介质阻挡放电协同催化两方面进行了概括总结。首先,简述了介质阻挡放电处理VOCs所用的驱动电源和等离子体发生器的研究现状及气体性质对VOCs降解性能的影响;其次,介绍了介质阻挡放电协同催化的两种方式（内置式和后置式）及各自情况下采用不同催化剂强化VOCs去除性能、提高能量效率、抑制副产物生成的过程机理;最后,分析了介质阻挡放电技术处理低浓度VOCs过程中存在的关键问题,并提出了未来的重要研究方向为：等离子体催化体系中VOCs的界面反应机理;催化剂的抗积碳性能的提高;适用于多组分VOCs的高效催化剂的开发。     

新型两级介质阻挡放电降解甲基橙的机理研究

采用新型两级介质阻挡放电(DBD)等离子体反应器对甲基橙废水进行降解处理,考察了甲基橙的p H值、电导率、降解率、化学需氧量(COD)随停留时间的变化。采用紫外光谱、红外光谱、液质联用对处理前后的甲基橙废水进行检测,并推测甲基橙降解机理。结果表明:甲基橙废水的p H值随着停留时间的增长而减小,电导率和降解率均随停留时间的增长而增大,甲基橙的COD值随停留时间的增长呈现先减小再升高最后降低趋于平稳的规律;经过表征分析,处理160 min后的甲基橙降废水中含有NO_3~-,HOOCCH_2CH_2CH_2CH_2CH_2SO_3~-,(CH_3)_2NCH_2CH_2CH_2CH_2CH_2COOH等。     

Surface treatment of sol-gel bioglass using dielectric barrier discharge plasma to enhance growth of hydroxyapatite

Surface treatment of sol-gel bioglass is required to increase its biomedical applications. In this study, a dielectric barrier discharge (DBD) plasma treatment in atmospheric pressure was performed on the surface of [SiO₂-CaO-P₂O₅-B₂O₃] sol-gel derived glass. The obtained bioglass was treated by plasma using discharge current 12mA with an exposure period for 30 min. The type of discharge can be characterized by measuring the discharge current and applied potential waveform and the power dissipation. Apatite formation on the surface of the DBD-treated and untreated samples after soaking in simulated body fluid (SBF) at 37 °C is characterized by Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), inductively coupled plasma (ICP-OES) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). We observed a marked increase in the amount of apatite deposited on the surface of the treated plasma samples than those of the untreated ones, indicating that DBD plasma treatment is an efficient method and capable of modifying the surface of glass beside effectively transforming it into highly bioactive materials.     

Some experimental parameters affecting performance of composite reverse osmosis membranes produced by plasma polymerization

Reverse osmosis (RO) composite polymer membranes were prepared from the organic monomers 3-butenenitrile, propyleneimine, 4-vinylpyridine, and allylamine by plasma polymerization in a radio-frequency discharge. RO performance data (water flux and salt rejection) were obtained as a function of discharge power and deposition time. Membranes were subject to RO testing at 45°C for up to 150 hr to investigate membrane deterioration. No appreciable degradation was observed. Water flux increased significantly with time at 45°C, and improved salt rejection at 45°C was observed in most cases.     

优化聚酰胺分离层制备高选择透过性反渗透膜

反渗透(RO)膜分离技术由于具有高效、低耗和产水水质高等优点,已成为现阶段解决水资源短缺的有效手段。进一步提高RO膜的选择透过性能有利于降低产水成本和提高产水质量,因此制备高选择透过性能的RO膜一直是膜领域研究的重点。从优化界面聚合工艺、优化基膜及开发新型制膜工艺三方面对近年来改善RO膜选择透过性能的研究进行了综述。通过优化界面聚合工艺和开发新型制膜工艺可以直接改变分离层的结构和性质,通过调节基膜的孔径、孔隙率及亲疏水性可以影响分离层的结构,从而改善RO膜的性能。最后对制备高选择透过性能的反渗透膜的研究方向与发展前景进行了总结与展望。     

Oxidative degradation of polyamide reverse osmosis membranes: Studies of molecular model compounds and selected membranes

Selected aromatic amides were used to model the chemical reactivity of aromatic polyamides found in thin‐film composite reverse osmosis (RO) membranes. Chlorination and possible amide bond cleavage of aromatic amides upon exposure to aqueous chlorine, which can lead to membrane failure, were investigated. Correlations are made of the available chlorine concentration, pH, and exposure time with chemical changes in the model compounds. From the observed reactivity trends, insights are obtained into the mechanism of RO membrane performance loss upon chlorine exposure. Two chemical pathways for degradation are shown, one at constant pH and another that is pH‐history dependent. An alternative strategy is presented for the design of chlorine‐resistant RO membranes, and an initial performance study of RO membranes incorporating this strategy is reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1173–1184, 2003     

A novel method of surface modification on thin-film composite reverse osmosis membrane by grafting poly(ethylene glycol)

A novel method of surface modification by grafting hydrophilic poly(ethylene glycol) (PEG) chains onto the surface of a thin-film composite (TFC) polyamide reverse osmosis (RO) membrane was performed. Aminopolyethylene glycol monomethylether (MPEG-NH₂) was used as grafting monomer. The membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The changes in chemical composition and morphology of the membranes' surface indicated the successful grafting process. Furthermore, a preliminary experiment confirmed that the grafting of PEG chains improved membrane antifouling property.     

Structure of porous cellulose acetate membranes and a method for improving their performance in reverse osmosis

Experimental data support the hypothesis that the surface layer of the asymmetric Loeb-Sourirajan type porous cellulose acetate membranes has a heterogeneous microporous structure. A general method is proposed for improving the performance of the above membranes in reverse osmosis, by which product rates are increased without decreasing solute separation. The method consists in pumping pure water past the back side of the membrane under just enough pressure for a sufficiently prolonged period of time; after such pretreatment, the membrane is used in the reverse osmosis experiments in the normal manner with the surface layer facing the feed solution. Back-pressure treatment at 400 psig for 85 hr on preshrunk and normally pressure-treated membranes increases the product rate by over 20% without decreasing solute separation in reverse osmosis experiments at 600 psig with the use of 0.5 wt-% NaCl–H₂O feed solutions; with a different sequence of back-pressure treatment, similar results have been obtained in reverse osmosis experiments at 1500 psig also. The compaction effect of a normal membrane and that of a back pressure treated membrane are the same during continuous reverse osmosis operation under 600 psig; the effects of back-pressure treatment on a normal membrane and a compacted membrane are also the same. The pure water permeability data obtained in cyclic experiments show that the smaller pores on the surface layer are opened more than the bigger ones during the back side operation. The probable structural changes taking place in the film during back-pressure treatment are discussed.     

Study of the structure and transport of asymmetric polyamide membranes for reverse osmosis using the electron spin resonance (ESR) method

The electron spin resonance technique (ESR) was used to study the structure and transport of asymmetric aromatic polyamide membranes. TEMPO (2,2,6,6-tetramethyl-1-piperridinyloxy free radical) was used as a spin probe that was brought into the membrane either by (a) immersion ofthe membranes in aqueous TEMPO solutions, (b) reverse osmosis (RO) experiments with feed solutions involving TEMPO or (c) blending TEMPO in casting solutions. The membranes were further tested for the separation of sodium chloride and TEMPO from water by RO. It was concluded that aromatic polyamide membranes contain water channels in the polymer matrix like cellulose acetate membranes. The presence of such water channels allows aromatic polyamide membranes to be used as RO membranes. The diffusion of organic solutes through the water channels seems much slower in aromatic polyamide membranes than in cellular acetate membranes, which probably causes a higher separation of organic solutes by aromatic polyamide membranes than cellulose acetate membranes. A comparison was made with other RO membranes (cellulose acetate, CA) and ultrafiltration membranes (polyethersulphone, PES). It was observed that the ESR technique can be used to study the structure of OF and RO membranes. The presence of water channels in the polymer matrix seems indispensable for the RO membrane.