PVDF中空纤维膜辐射接枝和交联及其对力学性能的影响

采用Co^60辐射引发丙烯酸接枝和PVDF中空纤维膜自交联,用IR谱图证实了丙烯酸接枝到中空纤维膜上.由SEM显示,低辐射剂量率有利于接枝链在膜表面的均匀分布,接枝率随辐射剂量率增加而下降,随单体浓度增加先上升,单体体积分数达到20%左右后接枝率反而下降;接枝膜的拉伸断裂强度随接枝率的增加而提高,但是辐射自交联无法显著提高膜的力学性能.     

Preparation and characterization of polyacrylonitrile-based membranes: Effects of internal coagulant on poly(acrylonitrileco-malefic acid) ultrafiltration hollow fiber membranes

Ultrafiltration hollow-fiber membranes (UHFMs) ofpoly(acrylonitrile-co-malefic acid) (PANCMA) were prepared by a dry-wet phase inversion process. The morphologies of inner surface and cross section for these hollow fibers were inspected with scanning electron microscopy. It was found that, by increasing the amount of solvent DMSO in internal coagulant, the number and size of macrovoid underneath the inner surface decreased. The water flux of the UHFMs also decreased while the bovine serum albumin rejection increased minutely. These results were interpreted based on the ternary phase diagrams for the PANCMA/DMSO/(H₂O+DMSO) system, which was obtained from the experimental cloud point measurements and empirical linearized cloud point relation. It was envisaged that the membrane surface could be further modified by the reaction of acid groups with poly(ethylene glycol).     

膜生物反应器研究进展

本文概括分析了膜生物反应器的特征、类型和功能,对其在发酵、动植物细胞培养帮生物催化等过程中的应用和发展做了介绍和讨论。     

The effects of spinning conditions on asymmetric 6FDA/6FDAM polyimide hollow fibers for air separation

We have found that the chemistries of inner and external coagulants, gelation bath temperature, and air gap distance have profound effects on 6FDA-polyimde hollow-fiber morphology and performance. This 6FDA-polyimide is made of 50 mol % 2,2′-bis(3,4′-dicarboxyphenyl) hexafluoro propane dianhydride (6FDA) and 50 mol % 2,2′-bis(3-aminophenyl) hexafluoro propane (4,4′ 6F-diamine) (6FDAM). An increase in air gap distance tends to induce three-dimensional open-cell pore formation. Raising bath temperature has a similar effect. Multilayer finger-void structure can be completely eliminated if one properly chooses a bore-fluid flow rate and a gelation bath temperature. Experimental data demonstrate that the location of the dense layer can be shifted from the inner skin to the outer skin based on the chemistry (solubility parameter) of coagulants. The location of finger voids is also dependent on the chemistry of coagulants, and the dense layer location may shift from the inner surface to the external surface or appear in both surfaces dependent on the differences in solubility and coagulation rate. A defect-free 6FDA/6FDAM polyimide fiber with a selectivity of 4.73 and a permeance of 38.1 GPU is produced. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1555–1569, 1997     

CMF系统处理生活污水厂二级出水

研究了连续微滤技术(CMF)在深度处理城市污水厂二级排放水中的应用前景,以某污水厂SBR(sequenting batch reactor)工艺二级出水为原水,着重考虑了CMF系统对水中OoD、SS、浊度等指标的去除效果,试验结果表明:CMF系统对水中COD有30%左右的去除率,出水浊度低于0.5 NTU.采用扫描电镜及能谱分析对膜污染物分析,得知膜表面的污染物以微生物和有机物为主.     

氨基酸中空纤维膜分配色谱模型

以色氨酸为例,考虑氨基酸解离和在中空纤维膜内扩散传质建立了氨基酸中空纤维膜分配色谱理论模型.该模型采用完全独立的模型参数,模拟结果与实验数据吻合较好,验证了模型的可靠性.理论计算表明流动相的pH值与局部氨基酸浓度密切相关;理论和实验结果表明,流动相离子强度对氨基酸的保留行为有很大影响,采用梯度洗脱的方式可以改善洗脱峰形,提高色谱柱的分离度.     

凝固浴温度对相转化聚醚砜中空纤维膜结构与性能的影响

以聚醚砜为膜材料、N,N-二甲基乙酰胺为溶剂、PVP为添加剂配成稳定溶液,使用水为凝固浴,采用干／湿法溶液相转化制备聚醚砜中空纤维膜．研究了凝固浴温度及空气间隙距离对膜的表面孔结构、断面结构和其它性能的影响．发现升高凝固浴温度的同时,增大空气间隙,可以有效地增大膜外表面的孔径,膜断面近外皮层下结构由指状孔向海绵状孔转化．     

Studies on the Extraction—Simultaneous Back-Extraction of Alkali Metal Picrates Using 1,3 Bis-Benzo-Crown-6-Calix[4] Arene in Hollow-Fiber Contactors

Abstract

An extraction and simultaneous back-extraction process with two hollow-fiber membrane contactors is evaluated for the continuous recovery of alkali metals and 1,3 bis-benzo-crown-6-calix[4]arene. The results show that this configuration operates as a “liquid membrane” (permeable only with alkali picrate) and order of the recovery yields is in agreement with the Donnan equilibrium. It is higher for the rubidium (75.8%) than for the cesium (68.1%) while it is only 11% for the potassium. This is a case where the high affinity of cesium picrate for the 1,3 bis-benzo-crown-6-calix[4]arene cannot be neglected and, as a consequence, its release in the back-extraction aqueous phase is more difficult. The effect of the alkali metal and the initial concentration on the system behavior shows that the concentration gradient controls the mass transfer. The kinetics are similar for the cesium and the rubidium whereas the mass-transfer resistance increases for the potassium. A high mass transfer in the first module can slow down the global-transport kinetics.     

Selective binding of docosahexaenoic acid ethyl ester to a silver-ion-loaded porous hollow-fiber membrane

Silver ions were loaded at a density of 1 mmol/g onto a sulfonic acid group-containing porous hollow-fiber membrane prepared by radiation-induced graft polymerization of an epoxy group-containing monomer with subsequent modification by reaction with sodium sulfite. The permeability (i.e., permeation flow rate per inside surface area of the hollow fiber) of 4.6% wt/vol bonito oil ethyl ester solution in water/ethanol (7.5:92.5, vol/vol) was 1.7 m/h at a permeation pressure of 0.1 MPa. Breakthrough curves (i.e., concentration changes of the effluent with increasing effluent volume) obtained with docosahexaenoic acid ethyl ester (DHA-Et) overlapped, irrespective of the permeation flow rate. This indicates that a higher rate of DHA-Et adsorption onto the silver ions on the membrane was attained with increasing permeation flow rate. DHA-Et, which was selectively bound to the membrane, was quantitatively eluted with acetonitrile as an eluent. The adsorption characteristics (i.e., binding rate, selectivity and durability for repeated use) of DHA-Et using the silver ion loaded porous hollow-fiber membrane were demonstrated. Feasibility studies will enable comparison of the purification cost of DHA-Et among the other purification techniques.     

聚偏氟乙烯中空纤维膜的改性研究

采用化学接枝方法对聚偏氟乙烯(PVDF)中空纤维膜进行亲水改性，采用红外光谱、X射线光电子能谱和扫描电子显微镜等对接枝层进行测试、表征，实验结果表明，PVDF中空纤维膜与2-丙烯酰胺-2-甲基丙磺酸发生了接枝反应，接枝物可有效提高PVDF中空纤维膜的亲水性；改性后PVDF中空纤维膜含水率提高至112．3％；pH值和溶液离子浓度对改性的PVDF中空纤维膜的通量有较为明显的影响。