膜分离技术在重金属废水处理中的应用研究进展

膜技术作为一种新型分离技术,在水处理领域得到了广泛的应用。文章综述了电渗析、液膜、反渗透、纳滤、沉淀-微滤、胶束增强超滤和聚合物强化超滤等各种膜分离技术的分离原理、特点,在重金属废水处理中的应用以及目前存在的问题。最后展望了膜技术在重金属废水处理领域的应用前景。     

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。     

投加粉末活性炭对超滤膜去除海水中有机物的影响

超滤膜的有机污染问题是膜法海水预处理技术在海水淡化工程应用面临的重要挑战,粉末活性炭吸附是目前常用的膜前预处理手段之一。本文对比分析了直接超滤和投加粉末活性炭后对海水中有机物的截留能力,利用三维荧光光谱分析了投加粉末活性炭对超滤膜截留有机物的影响机制,并考察了海水超滤过程中通量变化及膜污染情况。研究结果表明,投加粉末活性炭能够强化超滤膜对海水浊度和有机物的去除,当粉末活性炭投量为200mg/L时,整个系统对海水中DOC去除率从直接超滤时的55.1%提高到77.6%。利用粉末活性炭的吸附作用及其在超滤膜表面形成的疏松滤饼层能够显著提高超滤系统对海水中腐植酸类有机物的去除能力。与直接超滤相比,粉末活性炭-超滤系统对改善膜通量的作用有限,但粉末活性炭形成的滤饼层能够避免超滤膜与有机物直接接触,可显著减缓超滤膜的不可逆污染。     

新型膜分离技术的研究进展

膜分离技术是一项新兴的高效、快速、节能的新型分离技术。作为一种新型分离技术,在多种领域得到了广泛的应用。综述了反渗透、电渗析、纳滤、微滤、超滤、气体分离、渗透汽化和膜反应器等各种膜分离技术的分离原理、特点,在工业中的应用以及目前存在的问题。最后展望了膜技术的应用前景。     

电渗析过程传质模型的研究进展

电渗析是一种利用离子交换膜和电势差从溶液及其他不带电组分中分离出离子的物质分离过程,该技术具有适应性强、预处理简单、能耗低、环境污染小等优点,被广泛应用于化工、生物等领域的分离纯化过程。本文主要介绍了用于电渗析分离过程的6种传质模型,总结了各模型的优势及存在的问题,指出限制电渗析技术进一步发展的主要原因是对包含物质传递、浓差极化、流体流动行为、电解质溶液-膜平衡等复杂现象的电渗析过程进行理论和实验研究难度大,而传质模型化为电渗析分离过程的物质传递研究提供了一条有效途径,有助于深入研究电渗析过程中物质的传递机理,准确预测分离性能并导向性优化电渗析结构设计和操作工艺。并且提出未来电渗析传质模型的研究方向是结合经验方程或传质系数进一步优化传质模型,并采用仿真工具模拟传质过程,提高模型的准确性和普适性。     

膜分离技术原理及在水处理行业中的应用

介绍了近年来新型材料即膜分离设备的工艺技术特点、应用范围及其分离介质类型。详细、准确阐述了超滤膜、微滤膜、纳滤膜、反渗透膜、电渗析膜等设备的工作原理、技术特点和应用范围。     

基于膜技术分离纯化乳清蛋白的研究进展

乳清废水有机负荷高,若直接排放将引起严重的环境污染,且造成蛋白质资源的浪费。因此,乳清废水资源化利用日益受到人们的关注。本文简要介绍了乳清蛋白组成、特性及其应用,归纳了近年来膜技术在乳清资源化利用方面的应用。首先介绍了压力驱动膜技术中超滤和荷电超滤在乳清蛋白分离和浓缩方面的应用,此后重点介绍了电驱动膜过程中电超滤（EUF）和电渗析耦合超滤体系（EDUF）在乳清蛋白以及活性肽分离回收领域的应用最新进展,并针对乳清蛋白分离过程中的膜污染现象进行了分析,提出膜污染过程的影响因素及控制措施,以期为乳清的资源化利用提供有益参考。最后指出了膜技术在单个乳清蛋白的分离回收方面以及工业化放大等方面仍存在一定局限性,并对此提出了解决方案及其未来的发展方向。     

新型电渗析工艺的技术发展与应用

传统电渗析工艺在去除有害离子和脱盐领域虽具有明显的技术优势却也存在一定的技术限制。近年来,研究者相继开发了可原位产酸碱的双极膜电渗析、利用膜特性进行离子选择性分离的选择性电渗析、具有重组和浓缩离子能力的复分解电渗析、将化学差势能转化为电势差发电的逆电渗析等新型电渗析技术,同时又将光电池引入装置缓解了能耗问题。综述了各种新型电渗析技术的最新研究和应用领域,以期推动电渗析技术的应用发展。     

超滤膜分离技术在中药制剂生产中的应用

超滤作为典型的膜分离技术在中药制剂的生产中具有重要的应用价值。本文围绕超滤膜分离技术的原理、可行性、应用实例、存在的问题 ,以及发展趋势等方面进行了简要介绍和评述 ,指出基于筛分机理的超滤膜过程在中药有效部位和有效成分的提取分离中具有显著的技术优势 ,膜技术在中药制剂生产中应用的关键问题 ,包括设计制造适于中药工业化生产的专用膜装置、制定膜工艺和产品的质控标准和找到在中药生产流程中的最佳切入点     

PVDF超滤膜用于城市污水深度处理的试验研究

采用混凝沉淀-超滤组合工艺进行了城市二级出水深度处理的试验。结果表明,超滤膜对浊度、UV254、COD、PO43--P的平均去除率分别为100%、21.2%、28.36%、31.5%,超滤膜分离系统的产水率为84.6%。超滤前加混凝沉淀预处理,可以提高水中有机物的去除率,同时减轻了膜污染。     

Effect of solution flow velocity and electric field strength on chitosan oligomer electromigration kinetics and their separation in an electrodialysis with ultrafiltration membrane (EDUF) system

The aim of the present work was to study the effect of solution flow velocity and electric field strength applied to an electrodialysis with ultrafiltration membrane (EDUF) cell on chitosan oligomer electromigration kinetics and on chitosan oligomer mixture fractionation. It was shown that the effect of solution flow velocity was not significant, while the electric field strength showed a significant effect on each chitosan oligomer electromigration rate. The effect of the electric field strength was also significant on the separation possibility of the studied oligomers. It was shown that by using electric field strength of 2.5 V/cm, it was possible to obtain a solution composed only of the dimer and trimer until an operating time of 2 h. By increasing the electric field up to 5 and 10 V/cm, it was no more possible to separate the chitosan oligomers. Chitosan oligomer transport numbers were measured. It was found that they contribute to about 7% of total electric current carrying, while about 93% of the total electric current could be carried by the electrolytes. The system performance was also evaluated through electric field intensity measurement and membrane integrity evaluation. It was found that the membranes kept their integrity and no significant fouling was detected. EDUF appeared consequently as a very interesting and innovative technology for the separation at a large scale of oligosaccharide.     

Hemicelluloses separation from caustic-containing process stream by ultrafiltration

The present work aimed to study the performance of ultrafiltration (UF) membranes for hemicelluloses separation, from a caustic-containing highly alkaline, cellulose purification solvent stream of viscose rayon production process, and to understand the membrane behaviour, effect of multiple use cycle, identify potential performance drawbacks and propose possible solutions. Screening experiments showed that an UF membrane with a nominal molecular weight cut-off value of 3 kDa can be used to separate hemicelluloses from alkaline process stream. UF membrane was found to be prone to performance deterioration with time due to fouling. Higher feed temperature helped in improving the membrane flux values while maintaining hemicelluloses retention.     

A convenient method for the determination of molecular weight cut-off of ultrafiltration membranes

With the rapid increase of water contamination,membrane separation technology and their corresponding molecular weight cut-off (MWCO) evaluation method become more necessary.In this study,Panax notoginseng saponins was used as a new standard marker to determinate ultrafiltration (UF) membrane MWCOs,series of Millipore membranes were selected as control group to analyze and calculate the relationship between retention rate and MWCOs with exponential or logarithmic equation.A new and convenient method was provided for determining the membrane MWCO by modeling analysis retention rate with MWCOs,and the regression coefficients ≥0.990.The feasibility and practicability of established method was verified by different manufactures' membrane and dextrans.In the detection progress,as the main ingredient of Panax notoginseng saponins,Notoginsenoside R1,Ginsenoside Rg1,Ginsenoside Rb1and Ginsenoside Rd with different surface activity,the MWCO range of UF membranes can be divided into two zones mainly due to the retention rate difference among Notoginsenoside R1,Ginsenoside Rg1,Ginsenoside Rb1 and Ginsenoside Rd.Zone Ⅰ,1000-10000;and Zone Ⅱ,10000-100000.Thus,the new method would be helpful to improve the applicability of UF membrane in separation technology.     

陶瓷膜超滤薏苡仁混合油脱胶

研究了陶瓷膜在薏苡仁混合油脱胶中的应用。研究了不同截留相对分子质量陶瓷膜的脱胶效果以及过膜压力、料液温度和运行时间对膜通量的影响,并对陶瓷膜清洗工艺进行探索。选择截留相对分子质量15 000的超滤膜,在50 ℃和0.5 MPa下能够去除混合油中90%磷脂。用碱洗和次氯酸钠清洗能够彻底去除膜污染,恢复膜通量。     

电场强化制备荷电聚砜超滤膜及其性能

采用高压电场强化技术,结合相转化法制备荷电超滤膜。添加剂、溶剂与膜材料分别为聚乙烯吡咯烷酮(PVP K30)、N–甲基–2–吡咯烷酮(NMP)与聚砜(PSF),主要对膜分离性能受到高分子聚合物质量分数、凝固浴温度、电场强度等因素的影响进行了研究与分析。结果表明,高压电场强化不会改变膜的微观结构,但会影响膜的分离性能。实验得到最佳制膜条件:PSF质量分数为20%,PVP K30含量为6%,凝固浴温度为30℃,高压电场强化时间为40 s,电场强度为3 kV,此时,膜的分离性能达到最佳,膜的水通量为166 L/(m²·h),截留率为93.3%。     

电泳膜接触器研究进展

电泳膜接触器（EMC）是在传统电渗析器中引入多孔膜,或用多孔膜代替部分离子交换膜的一种新型膜分离技术,其中多孔膜作为两液流的接触界面,提供传质的场所,垂直于液流方向的电场是唯一的驱动力。本文介绍了EMC的工作原理,并简要概述了EMC的膜堆构型及运行模式。详细分析了进料液pH值、电场强度等操作参数、多孔膜的材质和截留相对分子质量等对EMC过程传质的影响,且对EMC运行过程中多孔膜的污染状况进行了探讨,并展望了EMC在生物大分子分离和纯化中的应用潜力。EMC中多孔膜的引入,使得EMC可以用于相对分子质量大于500 Da的生物分子的分离与纯化,进一步拓宽了电渗析的应用领域,而外加电场的作用能够有效减轻多孔膜的污染,因此,EMC在生物分子的分离与纯化方面具有广阔的应用前景。     

Nano SiO2 and TiO2 embedded polyacrylonitrile/polyvinylidene fluoride ultrafiltration membranes: Improvement in flux and antifouling properties

Polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) ultrafiltration (UF) membranes are widely used in drinking water and wastewater applications. These membranes are prone to fouling and membrane efficiency decreases with time under constant operation. Significant improvements/modifications are necessary to apply these polymers as sustainable membrane materials. In this study, PVDF and PAN UF membranes were modified through incorporation of nanoparticles (NPs) namely SiO₂ and TiO₂. PVDF and PAN UF membranes were prepared by phase inversion method from polymer solutions having dispersed SiO₂ and TiO₂ NPs in it. Membrane surface hydrophilicity, charge, roughness, and morphology were studied. Equilibrium water content and molecular weight cut-off of the membranes were also measured. Addition of NPs increased membrane surface hydrophilicity, equilibrium water content, and surface potential. NPs modified membranes exhibited better membrane flux (35–79% higher) and antifouling properties (flux recovery ratio values 28–41% higher) than the virgin membranes.     

Effect of Conditioning Ultrafiltration Membranes on their Performances in Electrodialysis with Ultrafiltration Membrane

Abstract

A recent alternative method based on ultrafiltration membrane stacked in an electrodialysis cell was recently used for the separation of bio‐active high added value charged molecules, such as peptides and polyphenols. However, the ultrafiltration membranes which are uncharged membranes present lower electrical conductivity, in comparison with conventional ion‐exchange membranes. The purpose of this study was to evaluate the effect of conditioning ultrafiltration membranes of different molecular weight cut‐off (MWCO) (10, 20, 50, and 100 kDa) in solution with different ionic strength (distilled water and 0.1 M NaCl_(aq)) on their electrodialytic properties. It appeared that the conditioning solution could have a major impact on the electrical conductivity value of an ultrafiltration membrane and that the final conductivity value after soaking increased with an increase in molecular weight cut‐off. However, the soaking period and solution had no effect on membrane thickness. Furthermore, the electrical conductivity of the membrane was increased after an electrodialysis with ultrafiltration membranes process of a salt solution.     

膜分离技术在低分子量生物产品分离纯化中的应用

介绍了膜分离技术在低分子量生产产品分离纯化中的应用。以压力差为推动力的膜分离技术包括微滤、超滤、纳滤、反渗透等，其分离性能通常由透过通量和截留率表征，而操作模式则分为浓缩和渗滤两种。本文将低分子量生物产品划分为氨基酸和多肽、抗生素、乳酸及低聚糖等，综述了膜分离技术在上述产品的回收、分离、纯化和浓缩过程中的研究与应用进展。     

Comparative analysis of the processes of collagen concentration by ultrafiltration using different types of membranes

Tangential flow filtration of the collagen protein solutions with a molecular weight 12, 14, and 24 kDa is investigated using flat sheet membranes. The effects of tangential ultrafiltration (UF) on the permeate properties using two regenerated celluloses (RCs) and two polyethersulfone (PES) membranes with molecular weight cut-off (MWCO) of 5 and 10 kDa are reported. The permeate and concentrate obtained in the UF experiments are characterized from a physical–chemical point of view by determining the temperature, pH, electrical conductivity, nitrogen content, and protein concentration. In addition, the experimental data are modeled using Hermia's model. The UF experiments demonstrated that permeate flux declined with increasing molecular weight of collagen at constant concentration (1%). Regardless of the molecular weight of collagen, the rejections decrease in the following order: PES 5 kDa > RC5kDa > RC10kDa > PES10kDa. In case of membrane with higher MWCO, the clogging phenomenon is mainly due to the blockage of the internal pores of the membrane than the formation of a polarization layer. Morphologies and characteristics of the membranes are characterized using scanning electron microscopy.