活性染料染色废水反渗透膜法处理试验研究

采用芳香聚酰胺/聚砜反渗透复合膜进行染色废水深度处理试验.结果表明,反渗透膜法可有效实现对活性染料(活性蓝MB-R)染色废水的深度处理和浓缩,膜对废水的脱色率接近100%,时废水中无机盐的脱除率大于95%,渗透液均为无色.膜面流速、跨膜压差,进液pH等工艺参数对反渗透膜法处理染色废水的性能影响较大,尤其是对平衡渗透通量的影响最明显.     

非均相催化氧化处理对苯二甲酸工业废水

采用非均相催化氧化法处理对苯二甲酸工业废水,研究了反应时间、氧化剂投加量、废水pH和废水起始浓度对CODCr去除率的影响.结果表明,以二氧化氯、次氯酸钠和双氧水作氧化剂,均可使废水的CODCr大幅度下降.采用不同的氧化剂时,废水的pH对CODCr去除率有明显的影响.在酸性条件下,用二氧化氯和次氯酸钠的CODCr去除率较高;而在中性条件下,采用双氧水的CODCr去除率较高.     

多巴胺改性的聚酰胺低压反渗透膜性能优化研究

研究了界面聚合中多巴胺对聚酰胺低压反渗透复合膜性能的影响,对影响膜性能的其他重要参数,如水相溶液组份浓度、p H、有机相溶液组份浓度,进行了优化研究。采用全反射红外光谱和X射线光电子能谱仪对低压反渗透膜表面化学结构组成进行了分析;扫描电子显微镜和原子力显微镜则对膜表面微观形貌结构做了表征;此外对膜片的表面亲水性和荷电性也做了测试;分析了膜表面微观结构和脱盐性能之间的构效关系。     

聚酰胺复合反渗透膜表面亲水化改性及性能影响

以丁二醇二缩水甘油醚、聚乙烯醇为单体,通过在聚酰胺复合反渗透膜表面进行交联亲水化改性处理,得到亲水性聚酰胺复合反渗透膜。考察了交联亲水化改性对聚酰胺反渗透膜形貌结构及性能的影响。以2000mg/L NaCl溶液作为进料液,在225psi压力下测试了反渗透膜片的选择渗透性能,同时在1000mg/L NaCl、150mg/L十二烷基磺酸钠(SLS)、1000mg/L牛血清蛋白料液条件下评价了膜片的抗污染性能。研究结果显示,通过对聚酰胺复合反渗透膜表面进行亲水化改性处理,膜片表面微观形貌结构出现明显变化,膜表面的粗糙度降低、亲水性增强,膜片的分离性能和抗污染性能得到明显的提升。     

苦咸水反渗透膜脱硼性能研究

对商业化的苦咸水反渗透膜片的脱硼性能进行研究,考察了进水pH值、压力、温度、NaCl浓度、硼浓度以及膜表面流速等对苦咸水膜脱硼性能的影响.结果表明:不同测试条件下苦咸水反渗透膜元件和膜片脱硼性能影响基本一致.在各种影响因素中,进水pH值影响最明显,脱硼率随着pH值的增加而大幅增大.在pH值小于10的条件下,脱硼率随进水...     

化学氧化法用于黄姜皂素废水生化处理出水的脱色研究

研究了化学氧化法处理黄姜皂素废水生化处理出水的脱色效果,考察氧化剂种类、投加量、pH值及接触氧化时间对脱色效果的影响。结果表明：常温时处理后出水色度指标均可达到国家行业标准,且最佳条件下次氯酸钠较双氧水具有更好的脱色效果,次氯酸钠处理成本也相对较低。     

为什么反渗透膜的性能会下降?如何处理?

正反渗透膜的性能下降主要原因是由于膜表面受到了污染,如表面结垢、膜面堵塞;或是由膜本身的物理化学变化而引起的。物理变化主要是由于压实效应引起膜的透水率下降;化学变化主要是由于pH的波动而引起的,如使醋酸纤维素膜水解、游离氯也会使芳香聚酰胺膜性能恶化。反渗透膜污染堵塞的主要原因是由于膜面沉积和微生物的滋长而引起的。其中微生物不仅堵塞膜,并对醋酸纤维素有侵蚀损害     

Desalination文摘 Vol.48 №1

控制浓度和pH,测量了商业反渗透膜对于臭氧和卤素消毒剂的敏感性,它是随膜聚合物类型、化学消毒剂和溶液pH的不同而变化。把卤素加到聚合物内的芳香环上,芳香聚酰胺膜被破坏,这一过程符合动力学效应。聚合物粘度的变化随膜损坏程度的增加而变化。对于反渗透装置,在考虑消毒作用的对策时,本研究结果将是很有用的。     

部分嵌入式静电自组装改性聚酰胺反渗透膜

针对聚酰胺反渗透膜(RO)抗阳离子表面活性剂污染能力差的难点,提出改变反渗透膜表面荷电性方法,以聚乙烯亚胺(PEI)的乙醇溶液为电解质溶液,利用部分嵌入式静电自组装法对聚酰胺反渗透膜进行改性。采用场发射扫描电子显微镜(FE-SEM)、X射线光电子能谱(XPS)、接触角和固体表面Zeta电位对改性反渗透膜的结构和性能进行表征。结果表明,FE-SEM图像显示膜表面形态没有发生变化;XPS元素分峰和含量分析证明了PEI成功组装在反渗透膜上;接触角验证了改性后膜的亲水性增加,Zeta电位证实了改性后膜的荷负电性减小。改性后膜通量和脱盐性能均增加,抗污染性能得到显著改善,并具有耐酸碱稳定性(pH 2～11)。     

氯化处理对高交联聚酰胺反渗透复合膜的影响

为了探讨氯化处理对高交联聚酰胺材料反渗透膜的影响,采用傅里叶变换红外吸收光谱分析、X射线光电子能谱以及SEM电镜扫描对氯化高交联芳香聚酰胺膜进行光谱分析。结果表明,1 690 cm-1和1 540 cm-1处有吸收,分别为酰胺吸收带I和酰胺吸收带II特征峰,经活性氯处理后,交联芳香聚酰胺在1 690 cm-1和1 540 cm-1处的吸收峰减小;同时在760 cm-1处出现C-Cl吸收峰。经pH=6.8、36 h活性氯化处理后,反渗透膜皮层外表面出现了塌陷的孔洞,内表面出现了较大的孔洞,孔洞直径约为800 nm左右;随着氯化处理强度的增大,孔洞直径增大。经150 h活性氯处理后,皮层内表面孔洞直径增至1 500 nm左右,复合膜分离层出现了明显的皮层与支撑层脱落的现象。     

芳香聚酰胺纳滤膜的制备及性能研究

以芳香聚酰胺为原料,采用相转化法制备了芳香聚酰胺纳滤膜,通过正交试验确定了最佳制膜工艺.详细讨论了纳滤膜的分离特性,并对纳滤膜的耐溶剂及抗污染性能进行了初步研究.实验结果表明,所制芳香聚酰胺纳滤膜对无机盐及小分子有机物具有较好的选择分离性能.操作压力为0.4MPa时,该膜对蔗糖的截留率为63.74%,对葡萄糖的截留率为54.36%.膜具有很好的耐溶剂性和抗污染性.     

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.     

Permselectivities of 2,2′‐dimethyl‐4,4′‐bis(aminophenoxyl)biphenyl diphenyl methane–based aromatic polyamide membranes for aqueous alcohol mixtures in pervaporation and evapomeation

The separation of aqueous alcohol mixtures was carried out by use of a series of novel aromatic polyamide membranes. The aromatic polyamides were prepared by the direct polycondensation of 2,2′‐dimethyl‐4,4′‐bis(aminophenoxyl)biphenyl (DBAPB) with various aromatic diacids, such as terephthalic acid (TPAc), 5‐tert‐butylisophthalic acid (TBPAc), and 4,4′‐hexafluoroisopropylidenedibenzoic acid (FDAc). The pervaporation and evapomeation performance of these novel aromatic polyamide membranes for dehydrating aqueous alcohol solution were investigated. The solubility of ethanol in the aromatic polyamide membranes is higher than that of water, but the diffusivity of water through the membrane is higher than that of ethanol. The effect of diffusion selectivity on the membrane separation performances plays an important role in the evapomeation process. Compared with pervaporation, evapomeation effectively increases the permselectivity of water. Moreover, the effect of aromatic diacids on the polymer chain packing density, pervaporation, and evapomeation performance were investigated. It was found that the permeation rate could be increased by introduction of a bulky group into the polymer backbone. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2688–2697, 2003     

Characterization of composite membranes by their non-equilibrium thermodynamic transport parameters

Composite reverse osmosis membranes were prepared by interfacially polymerizing aromatic polyamide discriminating layers on the inside surface of microporous polyethersulfone hollow fibers and on the surface of flat sheet polysulfone ultrafilters. The salt rejection and flux of these membranes were measured at various feed pressures. From these measurements, the membrane reflection coefficients, salt permeances and hydraulic permeances were estimated. Neither the polysulfone ultrafilters nor the microporous polyethersulfone hollow fibers possessed any inherent salt rejecting capability. Both had a hydraulic permeance at least two orders of magnitude greater than that of the respective composite membranes. Consequently, it was concluded that the estimated transport parameters for both composite membranes were characteristics exclusively of thier polyamide discriminating layers. Comparison of these transport parameters generated insight into structural and functional aspects of the membrane that could not be visualized by scanning electron microscopy.     

Preparation and characterization of thermally crosslinked chlorine resistant thin film composite polyamide membranes for reverse osmosis

Currently, polyamide reverse osmosis membranes are highly effective for desalination, industrial process water, and home drinking water. However, they have poor resistance to strong oxidants especially chlorine due to chain cleavage of aromatic polyamide. In general, aromatic polyamide RO membranes are essentially random copolymers consisting of the linear and crosslinked structures. The amide ring is sensitive to attack by chlorine because it is an electron-rich region. Therefore, the activated carbon or sulfite addition processes are essential to remove the chlorine in the separation processes. Many research groups have studied to improve the chlorine-resistance RO membrane having hydrophilic groups (− SO₃H and − COOH) or nitro groups (− NO₂) such as electron acceptors. In this study, thin film composite polyamide RO membranes were prepared by interfacial polymerization method including cross-linking agents having hydroxyl groups to improve the chlorine-resistance. The chlorine-resistance of polyamide RO membrane was influenced by the thermal cross-linking conditions (temperature and time) and cross-linking density of polyamide membranes.     

Surface Modification of Commercial Aromatic Polyamide Reverse Osmosis Membranes by Crosslinking Treatments

Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance. The crosslinking agents including 1,6-hexanediol diglycidyl ether, adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments. Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments. It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide II groups, which is confirmed by surface charge measurements. Based on contact angle measurements, crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface. With increasing amount of crosslinking agent molecules connected to membrane surface, the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity. The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane. Since the active sites (N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments, the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.     

Permselectivities of aromatic polyamide membranes for aqueous alcohol mixtures in pervaporation

The separation of water/alcohol mixtures was carried out using a series of fluorine-containing aromatic polyamide membranes. Aromatic polyamides were prepared by direct polycondensation of fluorine-containing diamine (2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, BAPPH) and various aromatic diacids. The separation factor toward water increased when the feed ethanol concentration was increased. The solubility of ethanol in aromatic polyamide membrane is higher than that of the water, but the diffusivity of water across the membrane is higher than that of alcohols. A separation factor of 83 and a permeation rate of 262 g/m²h with a 90 wt% feed ethanol concentration at 25 °C was obtained.     

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     

The effect of low molecular weight additives on the properties of aromatic polyamide membranes

Salts contained in aromatic polyamide solutions were found to have a considerable effect on the performance and structure of reverse osmosis membrannes cast from these solutions. As in cellulose acetate membranes, certain salts greatly increase membrane fluxes without a detrimental effect on rejection. Highly dissociated salts such as LiClO₄ or Mg(ClO₄)₂ exert a stronger influence than the commonly used LiCl. With mixtures of different salts, stronger effects may be obtained than with a single additive. Many experimental facts indicate that the “salt effect” in aromatic polyamide membranes is due to a general effect on solvent activity and thus on the kinetics and equilibria associated with evaporation and coagulation process.     

CONCENTRATION POLARIZATION OCCURRING INSIDE THE MEMBRANE DURING STEADY STATE PERVAPORATION

Experimental profiles of a single penetrant (water) across the membrane have been established at different downstream pressures during steady state pervaporation. The profiles ofacetic acid-water binary penetrant system across the membrane were also measured at different downstream pressures, temperatures and compositions during steady state pervaporation. A stack of identical pre-characterized symmetric aromatic polyamide membranes was used for the profile study. The theoretical prediction of concentration polarization from mathematical equations has been confirmed by the experimental profile data for a binary penetrant system.