Charged membrane ultrafiltration of heavy metal salts: Application to metal recovery and water reuse

An experimental investigation is presented of the thin-channel ultrafiltration of 0.6 × 10^?3 M to 15.0 × 10^?3 M aqueous solutions of Cu²⁺, Ni²⁺, or Zn²⁺ sulfate or chloride salts through a negatively-charged, non-cellulosic membrane. Multi-salt solutions and the actual rinse water from a Watts-type-nickel-plating process are also ultrafiltered. The membrane provides a Ni²⁺ rejection of 0.83 and water flux of 1.0 × 10³ cm/sec (23 gal/ft² day) at a transmembrane pressure difference of 4.0 × 10⁵ N/m² (3.9 atm). The membrane rejection and water flux data are utilized in a computer simulation procedure for scale-up to a multi-module, two-staged process for the closed-loop operation of a plating plant.     

Charged polyacrylonitrile membranes having amphiphilic quaternized ammonium groups for ultrafiltration

Four types of positively charged polyacrylonitriles having quaternized N,N-dimethylaminoethyl methacrylate (DAMA) were synthesized and were used to prepare ultrafiltration membranes by a phase-inversion method. The effect of aliphatic ethyl, octyl, and stearyl groups and the benzyl group, which covalently bind to the quaternary ammonium group, on filtration properties was studied by ultrafiltration under an applied pressure of 760 mmH₂O. Water permeability through the resultant membranes increased as the aliphatic chain length on the quaternary ammonium group increased. For a copolymer membrane having a benzyl group on the quaternary ammonium group, water permeability was lower than that for the ethyl type of copolymer membrane. The membrane permeability and pore size for the molecular size-exclusion effect were studied at various NaCl concentrations in the 0–0.15M region. The membranes having octyl and stearyl groups showed stable filtration behavior by increase of the NaCl concentration, while the membranes having an ethyl group and a benzyl group on the quaternary ammonium group showed a change of the water permeability due to a pore-size increase for the membrane by NaCl addition. Measurements of membrane potential indicated the shielding of positively charged sites of the membranes by salt addition. Further, the copolymer membranes showed a separation ability for water/2-butanol of low water content. The separation ability was attributed to the chemical structure of the membranes having different interaction characteristics with the mixture components. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1821–1828, 1998     

Charged membranes for ultrafiltration treatment of synthetic waste water containing peptone

Continuous ultrafiltration of synthetic waste water containing peptone was carried out by using positively and negatively charged polyacrylonitrile membranes. The filtration experiments were operated in cross-flow mode under 10 kPa of applied pressure. The filtration properties of the charged membranes were compared with those of uncharged polyacrylonitrile ultrafiltration membranes having similar molecular sieve characteristics and membrane structure to the charged ultrafiltration membranes. During the continuous filtration, the filtration rate decreased and the operation pressure increased because of the formation of a peptone gel layer on the membrane surface. It was found that, for the positively charged membrane, the decrease in the filtration rate of the charged membranes was smaller than that of the uncharged membrane. In addition, the positively charged membrane maintained the initial operation pressure during the filtration. The reduction of fouling in the positively charged membrane was discussed by analyzing the gel components on the membrane surface.     

Charged modified tight ceramic ultrafiltration membranes for treatment of cationic dye wastewater

Tight ceramic uitrafiltration membranes have been proven to exhibit good rejection performance for reactive dye wastewater at high temperatures because of their high thermal and chemical resistance.However,the application of ceramic membranes for the treatment of cationic dye wastewater is chal-lenging because of their surface charge.In this study,a ceramic membrane is modified by grafting aminosilane (KH-551) to enhance the positive charge of the membrane surface.The rejection perfor-mance of the charged modified ceramic membrane toward the methylene blue solution is significantly improved.The modification substance is bonded to the ceramic membrane surface via covalent bonding,which imparts good thermal stability.The modified ceramic membrane exhibits stable separation perfor-mance toward the methylene blue solution.Overall,this study provides valuable guidance for the adjust-ment of the ceramic membrane surface charge for treating industrial cationic dye wastewater.     

Determination of membrane areas for ultrafiltration processes

For batch mode ultrafiltration processes a numerical method for calculating membrane area has been devised with flux predicted from Flemmer's model. Erythromycin broth filtrate was used as a model fluid. Experiments at a 20 dm³ scale were used to estimate the parameters involved in Flemmer's equation, from which membrane areas appropriate for operations of 80 metric tons were calculated. Factors such as rejection, concentration ratio, etc, which affect the membrane size for batch operation, are discussed. The calculated results were consistent with experimental data at the 100 dm³ scale. For continuous operation equations for calculating membrane areas have also been established. The minimum membrane area was calculated at the optimum concentration ratios of each stage, usually their values were different at each stages. Comparison between batch and continuous mode in the context of the membrane area required is also discussed. The method could be applicable to other ultrafiltration operations. © 2001 Society of Chemical Industry     

聚醚砜超滤膜乳化法制备乳化柴油

采用平均孔径为25 nm的聚醚砜超滤(UF)膜,以去离子水为分散相,以0#柴油为连续相,分别以Tween-20和Span-80为分散相及连续相的乳化剂,采用膜乳化法制备W/O型乳化柴油。UF膜乳化法制备的乳液比传统乳化方法稳定时间提高2～2.5倍,而相同条件下乳化剂用量减少了50%～65%。此外,考察了UF膜法制备乳化柴油过程中的各工艺参数对乳液液滴大小、分布及稳定性的影响规律,结果表明:当乳化剂质量分数高于0.5%,连续相流速在2.0～5.0 m/s范围内,跨膜压差为0.02 MPa时,乳液分散系数α达到0.12～0.3,液滴尺寸为30～65 nm。     

超滤膜技术概述

当今社会,超滤作为一种新型膜分离技术,应用的领域十分广泛,而且也获得了良好的效果。本文首先介绍了超滤技术的原理、四大有机高分子膜材料和相转化制膜中常用的浸没沉淀法和溶剂蒸发法,然后简述了超滤膜的优点、四大领域的应用、三大污染物质及防治措施,并把超滤膜技术多年后的研究方向和未来前景总结出来。指出超滤膜具有在水处理净化、食品提纯和中药分离等方面的诸多优势,接下来在广泛总结颗粒物、有机物和微生物污染的基础上,通过针对性的污染类别,遴选出高效的处理措施,并且能够显著提升超滤膜的抗菌抗污染性能,从而为超滤膜发展和实践运用提供可能。文中提出：今后研究的重点将是制备高性能、低成本、绿色化的超滤膜,并与其他膜分离技术协同作用于生产生活。     

平板超滤膜元件的微分方程模型

以平板超滤膜元件的理想结构及传递过程的平衡方程为基础,建立了超滤膜元件运行的微分方程数学模型。在分析元件运行参数基础上确认了微分方程的边界条件,使微分方程组具有唯一解。膜元件微分方程模型的建立为超滤膜元件结构及运行分析提供了理论参考,并为超滤系统运行模拟软件的编制建立了数学基础。     

抗菌超滤膜的研究进展

为了改善超滤膜的使用寿命,其抗菌性能研究已成为近几年研究的热点。主要从膜表面改性和膜材料改性2个方面综述了抗菌超滤膜的制备方法,重点介绍了表面涂覆、表面接枝和共混法这3种常用改性方法的特点以及改性后膜的抗菌效果,并指出制备抗菌超滤膜所存在的问题,以及今后的发展方向。     

Polyacrylonitrile ultrafiltration membranes containing negatively charged groups for permeation and separation of dextran and dextransulfate

Ultrafiltration membranes of poly(acrylonitrile-co-sodium styrenesulfonate) [P(AN-co-SSS)] were prepared by casting the copolymer solution into water. The ultrafiltration rate of P(AN-co-SSS) membranes was controlled by adding poly(ethylene glycol) (PEG) of various molecular weights to the casting solution. The effect of the PEG addition on the membrane properties was examined. By using the P(AN-co-SSS) membranes, which possess various molecular weight cutoff (MWCO) properties, the permeation behaviors of dextran (D) and dextransulfate (DS) were compared. The P(AN-co-SSS) membranes markedly restricted the permeation of DS, owing to electrostatic barrier of the negatively charged groups in the membrane. The electrostatic sieve separation of DS and D, each having similar molecular size, with the membranes was also investigated. The membrane having negatively charged groups effectively rejected to DS with a high permselectivity. © 1994 John Wiley & Sons, Inc.     

A rational asymmetric hollow fiber membrane for oxygen permeation

A typical oxygen permeation hollow fiber membrane fabricated by phase inversion-based extrusion process demonstrates heterogeneous porous microstructures, in which the surface layer with relatively low porosity is used as a separation layer after sintering. It is usually not convenient to control the thickness of separation layer. And a high sintering temperature is needed to densify the separation layer, which in turn could destroy the desired porous microstructures in other portion. This paper studies a novel process to fabricate multilayer asymmetric hollow fiber membrane with a rational design using 67 vol. % Gd_0.2Ce_0.8O_2−δ−33 vol. % La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (GDC-LSCF) as a model material system. The phase inversion-based extrusion process in open literature is employed to fabricate a hollow fiber substrate featuring radially well-aligned microchannels open at the inner surface. Built upon the hollow fiber substrate, a thin dense separation layer and porous surface catalyst layer at shell side are then fabricated through dip-coating and sintering process alternatively. The oxygen permeation flux of the fabricated hollow fiber membrane reaches 2.68 mL/cm²/min at 900°C under Ar/air gradient, the highest performance of the membranes with GDC-LSCF material system in open literature. The innovative fabrication process is able to readily control the thickness of functional layers while decreasing sintering temperatures.     

一种基于膜污染指数的超滤膜污染评价方法

利用浸没式中空纤维膜小试系统,基于膜污染指数（FI）建立超滤膜污染的评价和试验方法。通过试验考察超滤膜污染变化规律,以及运行周期对膜污染指数计算的影响,并确定计算膜污染指数的运行周期;并对膜污染指数评价方法的可重复性进行检验：对化学清洗前后膜污染指数进行比较。试验表明,在过滤初期,滤饼污染和吸附污染并存,所以初期水力不可逆膜污染指数（HIFI）增长较快;中期超滤膜的吸附能力不断减弱,膜污染主要是滤饼污染,所以膜污染较为稳定：后期跨膜压力过大,压缩滤饼层,减小滤饼孔隙率,增加滤饼阻力,所以HIFI有所增加。同时短期的膜污染试验可以用来反映长期的膜污染情况,该超滤膜污染的评价方法重复性好,污染后的超滤膜经过化学清洗后。可以重复利用。     

超滤膜组件细菌截留性能测试方法研究

本文回顾了国内外在超滤膜细菌截留试验领域的研究成果,对中空纤维超滤膜组件的细菌截留检测进行了实验研究,以期为开展超滤膜组件细菌截留性能评价测试提供实验依据。     

Surface modification of polyacrylonitrile based ultrafiltration membrane

Ultrafiltration membrane based on polyacrylonitrile prepared by phase inversion method using zinc chloride as an additive showed more than 90% rejection for BSA and 90–110 lm^?2 h^?1 water flux. The surface modification of this membrane was studied using ethanolamine, triethylamine, sodium hydroxide, and potassium hydroxide solutions. The effect of base treatment time and temperature on water flux and rejection was investigated. The membranes exhibited swelling by NaOH treatment followed by deswelling by HCl post‐treatment, similar to pH responsive membranes. The treatment by organic as well as inorganic bases improved water flux with a slight lowering in BSA rejection by dead‐end mode type treatment. A 230% increase in water flux was achieved by sodium hydroxide treatment in crossflow mode without a noticeable pore swelling by SEM. The contact angle of the modified membranes was decreased as compared to the unmodified one indicating appreciable surface modification. As the treatment time or temperature increased, the ESCA analysis showed increased population of Na‐carboxylate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4378–4385, 2006     

N-乙酰化壳聚糖超滤膜的物理机械性能

以DMAc、乙酸酐、乙酰氯为乙酰化试剂对壳聚糖超滤膜进行乙酰化改性。结果表明，乙酰化壳聚糖超滤膜耐酸碱性均较好，乙酰化后膜的弯曲强度、湿状态下的拉伸强度、柔软性等物理机械性能均有明显提高，其中加入乙酰氯的壳聚糖膜湿态下的拉伸强度提高程度最大。     

N-乙酰化壳聚糖超滤膜的分离性能

采用DMAc、乙酸酐和乙酰氯为乙酰化试剂对壳聚糖超滤膜进行乙酰化改性，研究了乙酰化壳聚糖超滤膜对酸性红B的分离效率。结果表明，随着乙酰化试剂用量的提高，壳聚糖膜的截留率增大，而渗透通量则逐渐降低，其中加入乙酰氯后截留率提高程度最大，截留率可达99%以上，而渗透通量的降低程度最小。     

电渗析-超滤耦合技术研究进展

电渗析-超滤耦合技术（EDUF）是一项用于分离带电有机物的新型技术,用超滤膜替换一部分离子交换膜,或将超滤膜嵌入到传统电渗析器中,从而形成一种超滤与电渗析内部结合的新型分离技术。该技术一方面利用超滤膜的孔径差异性分离不同分子量的带电有机物,另一方面利用电驱动原理克服压力驱动式超滤膜的膜污染问题,在营养食品、生物制药等领域用于分离提纯活性有机物组分,展示出了良好的应用优势。本文聚焦于电渗析-超滤耦合技术的产生和发展,详细介绍了该技术的技术原理及应用优势,重点阐述了影响其分离效率的主要因素,包括pH、超滤膜切割分子量（MWCO）、电场强度、膜对结构等。最后,从提高分离效率、降低系统能耗、超滤膜材质、水解液预处理、系统泄漏等角度提出了未来的研究方向,为该技术的研究和应用提供指导。     

Separation of proteins by charged ultrafiltration membranes

The separation of a protein mixture by charged ultrafiltration membranes was studied. A negatively charged polymer was obtained by sulfonation of polysulfone, and a positively charged polymer was synthesized by chloromethylation of polysulfone and then by quaternization of the amino group. Then, the negatively and positively charged ultrafiltration membranes were cast from solutions of charged polymer/NMP(or DMF)/lithium nitrate. The molecular weight cut-off of the membranes were controlled by the changing casting conditions.

Single protein solutions were ultrafiltrated at the isoelectric point and at another pH level by the use of charged membranes. At the isoelectric point, rejection of the protein was low, while it was high at the pH level which gave the protein the same sign of charge as that of the membrane.

A protein mixture of myoglobin and cytochrome C was separated by the charged ultrafiltration membranes at the isoelectric point of one of the proteins. At the isoelectric point of cytochrome C, myoglobin has a negative charge. Thus myoglobin was rejected with a rejection of about 80% by the negatively charged membrane. At the same time, cytochrome C permeated completely through the membrane. Conversely, at the isoelectric point of myoglobin, cytochrome C has a positive charge and thus it was rejected with a rejection of about 20% by the positively charged membrane. The rejection of myoglobin here was almost zero.     

Application of ultrafiltration hybrid membrane processes for reuse of secondary effluent

This study evaluates the factors affecting pretreatment conditions for hybrid UF membrane processes for reuse of secondary effluent from the sewage treatment plant. The experimental results obtained from the ultrafiltration (UF) membrane process showed that the particles of the size range between 0.2 and 1.2 μm caused a significant impact on membrane fouling in all cases even with or without the coagulation process. As pretreatment of UF membrane process, the coagulation significantly improved the permeate flux. Optimal flux improvement was seen at an alum dose of 50 mg/L. In addition, it was found that the permeate flux was least declined under the coagulation condition of charge neutralization (pH 5.0). Also, the powdered activated carbon (PAC) adsorption enhanced the permeate flux. Application of the direct filtration as a pretreatment of UF membrane process was also very effective in reducing the UF membrane fouling.