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1.
The results of investigations on new polymer materials suitable for reverse osmosis are reported. The studies particularly concerned polypiperazinamides derived from differently structured bicarboxylic acids. Such polyamides show a water permeability that may vary from 0.09 μg cm?1 sec?1 to 2.3 μg cm?1 sec ?1 depending on the structure.The results obtained from reverse osmosis tests on dense and homogeneous films are described. Anisotropic membranes were prepared from poly(trans-2,5-dimethyl-piperazin-thiofurazanamide). Their properties very closely approach those of the corresponding cellulose acetate membranes. The anisotropic structure of the membranes has been evidenced by stereoscan electron microscope analysis.  相似文献   

2.
Performance of cellulose acetate membranes in reverse osmosis varies with the conditions under which they are cast. By varying casting solution composition and holding time in a systematic way, improvement in water flux at a given level of salt rejection has been obtained. Statistically designed experiments have been helpful in optimizing these two variables. A phase diagram of the cellulose acetateformamide-acetone casting system has been determined which gives the region of natural solubility of this three component system.  相似文献   

3.
郝丹宇 《工业水处理》2002,22(11):56-58
介绍了反渗透设备在应用中遇到的膜污染问题、清洗方案的制定及实施清洗后取得的良好效果。  相似文献   

4.
Polar (αp) and nonpolar (αn) parameters to characterize a variety of cellulosic and noncellulosic polymers have been developed from liquid chromatographic data on retention times for selected reference solutes in aqueous solutions. The above parameters give relative quantitative measures for the hydrogen bonding and nonpolar (hydrophobic) forces inherent in the chemical structure of the polymer molecule. Unique correlations are also shown to exist between the above parameters and Hansen's solubility parameters δh and δd for the polymers. These parameters and correlations offer significant guidelines for the choice of membrane material for reverse osmosis.  相似文献   

5.
Novel ultra-thin film (UTF) composite reverse osmosis (RO) membranes were fabricated in situ by the interfacial polymerization of poly-2-vinylimidazoline (PVI) precursors and aromatic acid chloride crosslinking agents. The syntheses of three different forms of PVI, which were used as precursors, are described. 3-(Chlorosulphonyl)benzoyl chloride, 3,5-di(chlorosulphonyl)benzoyl chloride and 1,3-benzenedicarbonyl dichloride were used as crosslinking agents. Both flat-sheet and tubular membranes were fabricated and tested for their salt retentions and permeate fluxes. The RO performances of the two sets of tubular membranes PVI I and PVI II crosslinked with 3-(chlorosulphonyl)benzoyl chloride, prepared according to optimized fabrication formulations, were recorded. These were 97.1 ± 0.1% retention; 730 ± 24 lmd flux and 98.2 ± 0.7% retention; 560 ± 150 L/m2/day (lmd) flux, respectively. The RO performances of initial tubular membranes made from PVI III and 3-(chlorosulphonyl)benzoyl chloride was 97.0 ± 1.1% retention and 643 ± 74 lmd flux.  相似文献   

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Two new series of thin-film composite reverse osmosis membranes have been developed and fabricated into spiral wound modules. The NTR-7100 series membrane is able to desalt sea and brackish water. The NTR-7250 membrane is designed for use at pressures below 20 kg/cm2. The membrane has a very high water permeability and is resistant to chemical and microbiological attack. In particular, the membrane is stable to chlorine, as shown by long-term reverse osmosis tests with tap water containing about 1 ppm of residual chlorine. The membrane has an unusual pattern of solute rejection. Salts containing divalent anions, such as sodium sulphate or magnesium sulfate, are rejected more than 98%; while salts with monovalent anions and bivalent cations, such as magnesium chloride, are rejected about 90% and salts with monovalent anions and cations, such as sodium chloride, are rejected 30–50%. Neutral solutes have relatively high rejection; for example, glucose, 90% and sucrose, <99%.  相似文献   

8.
Polyamide thin film composite membranes have dominated current reverse osmosis market on account of their excellent separation performances compared to the integrally skinned counterparts. Despite their very promising separation performance, chlorine-induced degradation resulted from the susceptibility of polyamide toward chlorine attack has been regarded as the Achilles’s heel of polyamide thin film composite. The free chlorine species present during chlorine treatment can impair membrane performance through chlorination and depolymerization of the polyamide selective layer. From material point of view, a chemically stable membrane is crucial for the sustainable application of membrane separation process as it warrants a longer membrane lifespan and reduces the cost involved in membrane replacement. Various strategies, particularly those involved membrane material optimization and surface modifications, have been established to address this issue. This review discusses membrane degradation by free chlorine attack and its correlation with the surface chemistry of polyamide. The advancement in the development of chlorine resistant polyamide thin film composite membranes is reviewed based on the state-of-the-art surface modifications and tailoring approaches which include the in situ and post-fabrication membrane modifications using a broad range of functional materials. The challenges and future directions in this field are also highlighted.  相似文献   

9.
Interfacial properties such as the thickness of interfacial water layer, the distribution coefficient of solute between interfacial and bulk water phases, and the volume of interfacial water per unit mass of polymer material have been identified as relevant physicochemical quantities governing reverse osmosis transport and determined by gas and liquid chromatography methods with respect to different polymeric membrane materials. They are further split into the contribution from the structural component of polymer repeating unit. Force constants A and D for sodium chloride, representing the repulsive force working between membrane surface and solute, have been calculated on the basis of inter-facial properties obtained above. Using these force constants, the pore sizes required to achieve 99.9% of sodium chloride separation are obtained for different polymeric membrane materials. Furthermore, the prediction procedure for the effect of preferentially adsorbed organic molecules on the separation of sodium chloride and product rate is illustrated as a model for “fouling” in the desalination process by reverse osmosis.  相似文献   

10.
H.K. Lonsdale 《Desalination》1973,13(3):317-332
A review is presented of the developments of the past several years in the area of reverse osmosis membranes. These developments have occurred along two lines: new membrane materials and new membrane fabrication methods. Among the new materials can be cited aromatic polyamides, polybenzimidazole, polyphenylene oxide, hydrated metal oxides, crosslinked and blended cellulose acetates, crosslinked polyvinylpyrrolidone, crosslinked polyethylenimine, and derivatives of several of these materials. The water and salt permeabilities of many of these materials and of the cellulose acetates are compared.Important developments in the area of fabrication methods include the extension of asymmetric membrane techniques to new materials, supported ultra-thin films, hollow fibers and asymmetric hollow fibers, and dynamically formed membranes. A comparison of these materials and fabrication methods requires some kind of figure of merit and one such parameter is discussed.  相似文献   

11.
Small colloidal particles intermediate in size between suspended solids, and true dissolved solids have been causing serious problems to many reverse osmosis systems throughout the world.These tiny negatively charged particles become concentrated at the surface of the membrane during the R.O. process and begin to coagulate, plugging the membrane. If this fouling is allowed to go on unchecked, the quantity and quality of the product water will begin to deteriorate until the membranes will eventually need to be replaced.In order to prevent this from happening, it is suggested that the R.O. pretreatment system be designed properly. If the pretreatment is not adequate, it can lead to high maintenance costs and an increase in membrane replacements.  相似文献   

12.
A new group of asymmetric non-cellulosic membranes having a performance intermediate between that of a conventional RO membrane and an ultrafilter has been developed. Its main characteristics are high fluxes (4–10 m3/m2 day) at low pressures (6–10 at) and moderate rejections for various salts. From 200 mg/l solutions of NaNO3, Na2SO4 and KH2PO4 rejections up to 40%, 70% and 90%, respectively, were obtained. The new membranes can withstand large variations in pH (1 to 13) and have excellent chemical and biological stability. The membranes have been tested in a mobile SUF pilot plant operating on oxidation pond effluent. High rejections for BOD, COD, bacteria and suspended solids as well as a 20% reduction in salinity have been obtained.  相似文献   

13.
A composite reverse-osmosis membrane has been developed for seawater desalination having a 400-Å semipermeable barrier. The membrane is prepared by directly forming a very thin film of a polymer, generally cellulose triacetate, upon the finely porous surface of a supporting membrane. The composite membrane, capable of desalinating seawater in a single pass, has demonstrated improved flux stability at high pressures over modified membranes currently used to desalinate brackish water.  相似文献   

14.
Copolyamides were prepared from mixed diamine components of 3,3′‐ or 4,4′‐diaminodiphenylsulfone, piperazine, and dichlorides such as isophthaloyl or terephthaloyl. The obtained copolyamides are random copolymers, which have good solubilities in organic solvents and good mechanical properties, even in water. The asymmetric membranes prepared from the copolyamides [ex: 4I‐PIP(20)] not only have more excellent reverse osmosis performance, but also higher chlorine resistance than NOMEX‐type aromatic polyamide. New membrane materials with excellent reverse osmosis performance and higher chlorine resistance than the NOMEX‐type aromatic polyamide could be demonstrated successfully. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1357–1364, 2000  相似文献   

15.
综述了近年来反渗透膜有机污染控制方法的研究进展,其中进水预处理、优化操作条件、添加阻垢剂、膜表面改性和清洗对反渗透膜的有机污染均能进行有效的控制,提出了反渗透膜有机污染控制方法的研究方向。  相似文献   

16.
Membranes of graft copolymers of polyethylene with poly(sodium styrene sulfonate), poly(4-vinylpyridinium methyl bromide), and poly(sodium acrylate) were prepared by using the technique of peroxide grafting. The reverse osmosis characteristics of the membranes were examined as a function of grafting yield. In these membranes, the grafting can be considered as a process of introducing ionic sites, and it depends on the conditions of the grafting reaction, such as monomer concentration and temperature. However, the overall reverse osmosis characteristic is not only dependent on the number of ionic sites introduced but also on the swelling capability of the membrane. Consequently, the salt rejection of grafted membrane of a fixed graft yield depends on the conditions of the grafting reaction. All grafted membranes which have grafting yields above a certain value behave as normal ionic polymer membranes, and their interrelationship of salt rejection and water permeability follow the general dependence found for ionic polymer membranes.  相似文献   

17.
Dynamic formation of Polyacrylamide membranes on a Millipore filter in the reverse osmosis was optimised concerning rejection of a standard NaCl water solution.Optimised membranes were tested under 70 bars with selected salts in single-solute water solutions.Exclusion of salts with alcali cations depend on the kind of anion and is in the order SO2-4 > F- > HCO-3 > Cl- > NO-3 > J-.Rejection of salts with alkaline earth cations is generally lower than corresponding salts with alcali cations.Especially concentration dependence of rejection of SO2-4 and NO-3 through these membranes was tested using different cations.Remarkable is the relatively high rejection of Na2SO4, which is 93,6% for a 5 g/l water solution under a flux of 820 l/m2· d.Dynamic PAA membranes are not useful for sea water desalination but they could be used for treatment of water with higher SO2-4 content.  相似文献   

18.
A mathematical model predicting flux decline of reverse osmosis membranes due to colloidal fouling has been verified. This mathema- tical model is based on the theory of cake or gel filtration and the Modified Fouling Index (MFI). Research was conducted using artificial colloidal solutions and a pilot plant equipped with ultrafiltration membranes. Polystyrene latex spheres, having a size of about 0.05-0.08 μm were used as a foulant.The result of this research was, that the measured and calculated values of flux decline of the ultrafiltration membranes as a function of time agree reasonably well. The difference between the measured and calculated values may be explained by the assumption, that initially blocking filtration occurs instead of cake or gel filtration.  相似文献   

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