Preparation of zeolite A membranes by microwave heating

Molecular sieve membranes consisting of NaA zeolite crystals have been successfully synthesized on symbol -Al₂O₃ substrate by means of microwave heating. In this way, the reaction time is greatly reduced to only 15–20 min and the membranes obtained are very stable and dense. Moreover, the thickness of the membranes can be easily controlled by varying the amount of the reaction mixture. To study the formation process of the membranes, the samples in various reaction stages have been characterized by field emission scanning electron microscopy and X-ray diffraction.     

氯霉素分子印迹复合膜的制备及其吸附性能研究

利用分子印迹原位聚合法,在紫外光引发下,以氯霉素为模板分子,以甲基丙烯酸二乙基氨基乙酯为功能单体,以乙二醇二甲基丙烯酸酯为交联剂,以偶氮二异丁腈为引发剂,以尼龙微孔滤膜为载体,制备了具有选择识别性的氯霉素印迹聚合物复合膜;采用紫外光谱分析研究了模板分子和功能单体之间的作用,并对印迹聚合物复合膜进行了平衡吸附和特异性吸附实验,以研究其识别能力。结果表明,氯霉素和甲基丙烯酸二乙基氨基乙酯之间形成了非共价键;合成的印迹复合膜对氯霉素分子表现出了高度的识别能力和良好的特异吸附性,吸附结合量达到1.753 g/cm2。     

The effects of performance and cleaning cycles of new tubular ceramic microfiltration membrane fouled with a model yeast suspension

The efficiency of crossflow microfiltration processes is limited by membrane fouling and concentration polarization leading to permeate flux decline during operation. The experiments that were carried out in the laboratory were conducted to determine and investigate the performance, behaviour and the fouling susceptibility of new ceramic tubular microfiltration membranes during the crossflow filtration of yeast suspensions. The tubular membranes of nominal pore size 0.5 microns were fouled over a varied range of concentration, temperatures, pH, crossflow velocities and system pressures. The typical filtration conditions were at a temperature of 25°C, a system pressure of 1.5 bar and a concentration of 0.03 g/L yeast suspension. These parameters varied during subsequent investigations. After each experiment, the membrane and the rig were cleaned using a three stage cleaning process and was reused in order to replicate industrial filtration conditions. The effects of repeated fouling and cleaning cycles upon membrane flux over time and cleaning efficiency are investigated and their influence over time is also documented. For every experiment, the flux data was recorded over a 50 min period and the membrane was changed after the PWF declined considerably due to excessive fouling over time. Chemical cleaning consisted of a sequential application of a 1% caustic solution through the rig followed by a 2% hypochlorite solution and a 2% nitric solution, all at 50°C. The permeate flux was shown to decrease with filtration time during the development of the fouling layer. Once the fouling layer was developed and established, there appeared to be a leveling of permeate flux. The experimental results are presented in the report and the flux values at different conditions are presented.     

聚丙烯腈/聚砜共混膜的制备及其结构表征

采用粘度法和红外光谱法研究聚丙烯腈(PAN)/聚砜(PS)的相容性,研究聚合物组成,共混物浓度,添加剂,凝胶浴等对PAN/PS共混膜的水通量和截留率的影响.采用扫描电镜分析PAN/PS共混膜的显微结构.结果表明:PAN/PS共混膜与PAN膜具有相似的化学稳定性,但较PAN膜具有更好的分离和透过特性.     

乳状液膜法提取Cr3+内相界面反应的研究

文章对乳状液膜法提取Cr3+内相界面的反萃取反应进行了研究。选择NaOH为反萃剂,H2O2为氧化剂,研究了内水相pH值、反应温度、搅拌速率、原料配比对反萃反应的影响,同时研究了反萃反应的反应方程式、反应的热力学性质。实验表明,反萃反应达平衡时的分配比随内相水溶液pH值及搅拌速度的升高而降低,随反应温度的升高而升高,随NaOH与[CrHn-mL(O)]2+摩尔比的增加先降低后升高;通过斜率法确定反萃反应为氧化-还原反应,并得到了反应的表观平衡常数k;计算了反萃反应的热焓ΔH,自由能ΔG和熵变ΔS。     

木粉对缓释化肥包膜透过能力的调控

采用48μm和150μm木粉为填料制备了聚苯乙烯/木粉复合膜,考察了木粉含量、复合膜厚、木粉粒径对复合膜透过性能的影响。结果表明,木粉可以很有效地调控聚苯乙烯膜对尿素的透过能力,复合膜对尿素的透过速度明显大于纯聚苯乙烯膜的透过速度;随着木粉含量的增加,复合膜对尿素的透过速度增加。光学显微镜观察发现,木粉中纤维状结构明显,复合膜在水中浸泡后其中木粉吸水溶胀,成为复合膜中尿素透过快速通道。     

共混氧氮分离膜的研究进展

列举了无机、有机氧氮分离膜的研究进展,重点介绍了有机无机共混氧氮分离膜的研究现状、共混膜存在的问题和解决方法以及用于预测共混膜渗透性质的Maxwell模型和其改进形式,并提出了共混氧氮分离膜未来的发展方向.     

正交实验法优化制备复合荷电镶嵌膜

以聚醚砜为基膜,以聚环氧氟丙烷胺及2,5-二胺基苯磺酸混合水溶液(无机相)与三酰氯的正己烷溶液(有机相)通过界面聚合反应,制备了一种新型的复合荷电镶嵌膜.采用正交设计实验方法,研究了界面聚合条件如界面聚合单体的浓度及界面聚合反应时间对膜性能的影响.结果表明:三酰氯的浓度对膜性能的影响最为显著,其次是界面聚合时间,而聚环氧氟丙烷胺的浓度对膜性能的影响最小.优化后所制备的复合膜对盐类的截留率较低(均低于40%).膜能截留低相对分子质量有机物而透过盐,说明该膜可用于盐类与有机物的分离.     

Synthesis and reactive features of a terpolymer: Poly(N‐vinyl‐2‐pyrrolidone‐co‐vinyl acetate‐co‐glycidyl methacrylate)

A polyvinyl pyrrolidone terpolymer system is described that can be chemically cross‐linked at moderate, 70–100°C, temperatures. The system has significant potential for development of durable long‐lasting pyrrolidone coatings in a wide range of applications, particularly in water filtration membrane construction where leaching is an unresolved, serious problem. The synthesis of the terpolymer, poly(N‐vinyl‐2‐pyrrolidone‐co‐vinyl acetate‐co‐glycidyl methacrylate), by free radical polymerization is described. The reactive features of this terpolymer are presented in the context of acidic anhydride curing. In a polar aprotic solvent, the terpolymer is reacted with poly(methyl vinyl ether‐co‐maleic acid) and cured thermally. Key aspects of the terpolymer synthesis and the acid anhydride cross‐linking reaction using DSC, rheology, FTIR, and a small molecule model system to study the cross‐linking chemistry are presented. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Investigating the membrane morphology of water/solvent/nylon 6 systems

In this study, nylon 6 membranes were prepared in a water coagulation bath with two types of solvents, CaCl₂–methanol (CaClMe) and formic acid (FA). The morphology of the membranes, which was controlled by the phase behavior of their solutions, were connected to the mechanism of demixing, including liquid–liquid and liquid‐crystallization. Ternary phase diagrams showed that the CaClMe system coagulated significantly faster than the FA system. As observed by scanning electron microscopy, the CaClMe membrane had a porous, interconnected pore structure with macrovoids, whereas the FA membrane had a dense, spherulitic surface with a closed cell morphology. The high reaction surface of the CaClMe membrane with dye molecules provided outstanding dye rejection. Also, thermal analysis by differential scanning calorimetry showed that the slow coagulation of the FA system facilitated the formation of stable α‐form crystals rather than a metastable γ‐form structure. The results show that the phase‐separation mechanism was switched from liquid–liquid to liquid‐crystallization through a change in the solvent type from CaClMe to FA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013