焦化生化出水电渗析脱盐研究

采用电渗析技术对焦化生化出水如曝气生物滤池出水及反渗透浓水进行脱盐,考察不同废水中的离子迁移、废水脱盐及离子交换膜污染情况。结果表明:2种焦化废水采用电渗析处理具有较好的脱盐效果,其中不同离子的迁移脱除与其浓度、离子半径等密切相关。膜电阻测试表明,不同焦化废水电渗析体系中不同离子交换膜的污染存在差别。扫描电镜和红外分析表明,曝气生物滤池出水主要由有机物造成阴离子交换膜污染,而反渗透浓水主要在电渗析浓室侧的膜表面形成颗粒状的无机污染,且阳膜浓室侧比阴膜浓室侧更显著。     

阴离子交换膜改性及抗污染性能研究进展

电渗析技术应用于工业废水脱盐时,废水中有机物及其它杂质组分等会造成膜污染,进而影响脱盐性能。电渗析膜污染防治对促进电渗析在工业废水处理中的应用有重要意义。相比于阳离子交换膜,阴离子交换膜更易形成有机污染,且更严重。阴离子交换膜污染主要由腐殖酸、牛血清蛋白、阴离子表面活性剂等有机物造成,污染过程主要受静电作用、亲和作用和几何因素的影响。膜改性提高阴离子交换膜的抗污染性能是电渗析膜污染防治的有效方法,目前已有许多有关膜改性提高阴离子交换膜抗污染性能的报道。膜改性方法主要有化学改性法、等离子体改性法、表面涂覆改性法、电沉积改性法、自聚合改性法及改进基膜结构法等。本工作对阴离子交换膜改性及抗污染性能的研究进展进行了综述,对不同改性方法的优缺点进行了分析和评价。这些改性方法能提高阴膜表面的负电荷密度和亲水性、降低膜表面粗糙度和基膜含水率等,因此可以改善阴离子交换膜的抗污染性能。然而,目前研究获得的改性阴离子交换膜仍存在修饰层不稳定、抗污染性能不理想和性能测试不系统等缺点,需进一步优化改性方法、改性工艺、组分修饰及性能测试等,以获得抗污染性能稳定且效果良好的改性阴离子交换膜。     

腐殖酸聚集体对膜蒸馏过程膜污染的作用机理

膜污染是膜蒸馏过程应用于工业水处理中遇到的主要问题之一。选取水体中具有代表性的有机物（腐殖酸）、微溶无机盐（碳酸钙）作为典型污染物,研究有机腐殖酸聚集体对于膜蒸馏过程膜污染进程的影响规律,探讨天然有机物-无机微溶盐混合水体中腐殖酸聚集体对于无机盐结晶过程的控制机理。结果表明：膜蒸馏通量的衰减大致可分为由滤饼层的形成造成的不可恢复部分以及由浓差极化、膜孔“半润湿”而造成的可部分恢复的通量降低。Ca²⁺通过加速腐殖酸分子的聚集过程,使表面负电性降低的腐殖酸聚集体率先吸附在聚偏氟乙烯中空纤维膜内表面,形成有机基质污染层;碳酸钙在有机腐殖酸聚集体的诱导下在膜内表面异相成核,最终成长为稳定的晶体。腐殖酸聚集体为无机盐晶体在疏水性膜内表面的生长提供了异相成核的基础。可通过控制污染水体中有机物的含量控制微溶碳酸钙在膜内表面成核及生长,实现控制其在膜内表面附着进而诱发疏水膜发生亲水化的过程。     

SiO2/PVDF离子膜的选择透过性

高分子有机聚合物聚偏氟乙烯(PVDF)以其优良的物理化学性能而倍受青睐。但由于PVDF膜的疏水性,应用在水处理中时容易产生污染,使其应用受到了限制。制备了有机无机SiO2/PVDF离子膜。通过测试膜浓差电势,确定膜对离子的选择透过率和膜表面电荷密度。结果表明,添加纳米SiO2能提高PVDF膜对离子的选择透过率,但只有加入SiO2质量分数为0.21%时,离子膜的选择透过率和表面电荷密度才适宜。SiO2/PVDF-0.21离子膜电渗析对不同离子的去除效果试验表明,该电渗析对多组分离子溶液体系的离子总去除率达到了93.7%。     

电渗析法处理高含盐有机废水中有机物迁移研究进展与发展方向

综述了高含盐有机废水电渗析处理过程中小分子有机物迁移机制的研究进展,分析了不同无机盐体系中电流、电压、有机物初始浓度以及pH等因素对有机物分离及去除效果的影响,梳理了电渗析过程中有机物膜污染趋势,并展望了电渗析处理高含盐废水的发展方向。     

碟管式纳滤膜在生活用水处理中的膜污染特性

采用碟管式纳滤膜对生活用水进行深度处理,研究了不同操作条件对元件分离性能及产水水质的影响,得到最佳运行条件为运行压力1MPa、进水温度为25℃以上、最小浓水流量300L/h。对原水水质进行分析,有效预测了污染物成分及膜污染情况,提出了预处理系统的设计及清洗方案。运用扫描电镜、EDS能谱、红外光谱及三维荧光光谱分析出,从进水端至出水端膜污染逐渐加剧,污染物成分主要以有机污染为主,并且含有难溶盐析出结晶的无机污垢及一定程度的生物污染。对碟管式纳滤膜在生活用水处理中膜污染特性的研究,分析污染成因为难溶盐随浓度增加在膜表面析出形成无机结垢,大量有机物在膜表面吸附形成有机污泥层,而水中微生物或细菌等在膜表面滋生造成生物污染,污染形成顺序为有机污染率先在膜表面形成,随后形成无机污垢,并且会发生相互作用,其结果导致膜通量下降、产水水质变差。本研究借助中试试验探究了碟管式纳滤膜元件的污染特性,为这种新型膜元件在实际生产中如何高效使用及有效控制纳滤膜污染提供依据。     

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。     

电渗析水处理的基本知识 第三讲 电渗析器的调试和操作运行

沉淀结垢,是危及电渗析器安全运行的主要问题。膜表面的浓差极化,是产生沉淀结垢的主要原因。电渗析器运行时,在直流电塌的作用下,水中的阴、阳护离子分别在膜间进行定向移动,各自传递着一定数量的电荷,形成电渗析器内的操作电流。当操作电流过大(或隔室内水流状态不佳     

钢铁废水溶解性有机物解析及其对反渗透膜的污染行为

针对钢铁废水深度处理工艺中超滤-反渗透处理单元反渗透膜元件有机污染问题,采用大孔吸附树脂分离法,将反渗透进水中的溶解性有机物进行分离,得到分别含疏水碱性有机物、疏水酸性有机物、疏水中性有机物和亲水性有机物的4个组分,对其进行组成分析并探究其对反渗透膜的污染行为。其中,亲水性有机物含量最高、疏水中性有机物含量最低。与亲水性有机物相比,疏水性有机物分子中含有更丰富的芳香结构或其他共轭结构,疏水酸性有机物芳香化程度最高。疏水中性有机物与膜表面疏水-疏水相互作用导致其易于在膜表面吸附,造成的通量衰减率最高,且水力清洗通量恢复率最低。含亲水性有机物组分造成的通量衰减率仅次于疏水中性有机物组分,因其有机物浓度较高、含亲水性有机物亲水性基团与膜表面氢键作用易于导致膜污染,而膜表面水力剪切作用有利于降低亲水性有机物污染层厚度和透水阻力。因此,疏水中性有机物和亲水性有机物是造成膜污染主要的溶解性有机物。可通过优化反渗透系统进水预处理工艺,强化去除疏水中性有机物和亲水性有机物,有望更高效地减轻反渗透膜污染。     

电渗析中的膜污染及其控制方法研究进展

电渗析作为一种膜分离技术,因其不消耗药品、无废液产生已被广泛用于盐溶液脱盐及环境和生物技术工业领域,但膜污染始终是限制电渗析技术应用的主要因素.从引起电渗析过程中膜污染的物质、膜及料液性质、操作条件等方面分析了膜污染的成因和污染后果,并对电渗析过程中膜污染的分析方法及防治措施进行了较为详细的综述.     

Effects of silica sol on ion exchange membranes: Electrochemical characterization of anion exchange membranes in electrodialysis of silica sol containing-solutions

The fouling potential of the negatively charged silica sol in electrodialysis (ED) by adsorption on the surface of an anion exchange membrane was investigated. Since the fouling potential is related to the physical and electrochemical properties of the silica sol and anion exchange membranes, it is important to characterize the properties of silica sol and membranes. The surface charge of silica sol was investigated by the electrophoretic mobility and its isoelectric point was determined as pH 3. The commercial anion exchange membranes were characterized in terms of exchange capacity, water content, the zeta potential and the electrochemical properties of the membranes using impedance spectroscopy to predict the effects on the electrodialysis performances. Among the characterized properties, exchange capacity and some electrochemical properties of the anion exchange membranes were rather improved after ED experiments. In the electrodialysis of solution containing silica sol, deposition of the silica sol did not decrease the desalting performance of the anion exchange membranes because of loosely packed cake layer on the membrane surface.     

Characterization of anion exchange membranes with natural organic matter (NOM) during electrodialysis

Natural organic matter (NOM) is thought to be a major source of fouling during membrane filtration of natural waters. The organic matter present in surface waters was characterized in terms of its molecular weight distribution, acidity and electrokinetic properties. The fouling potentials of anion exchange membranes were predicted by the characterization. Changes in the physicochemical properties of anion exchange membranes were also examined during electrodialysis (ED) process of solutions containing NOM. The ED performances were evaluated for the three anion exchange membranes (AMX, AM-1 and ACM) in the presence of NOM. Fouling phenomena in terms of current efficiency and NaCl flux were in good agreement with the fouling potentials predicted by the characterization results. Observations of the molecular weight distribution and the constituents of NOM revealed that the hydrophobic NOM fraction with high molecular weights deposited mainly on the membrane surface, providing fouling effects on the anion exchange membrane.     

A study on fouling mitigation using pulsing electric fields in electrodialysis of lactate containing BSA

Fouling tendency in electrodialysis was investigated using the electrochemical and physical properties of the foulants and ion exchange membranes. It was found that bovine serum albumin (BSA), a large molecular weight protein, fouled the AMX membrane irreversibly by deposition on the membrane surface. Electrodialysis experiments of lactate with 1.0 wt% of BSA were performed using the square wave powers at different frequencies to examine the pulsing power influences as a fouling mitigation method, and the results were compared with the data obtained using the DC power. Reduced fouling potentials were observed when the square wave powers were used in the electrodialysis of lactate and confirmed the membrane fouling index for electrodialysis (EDMFI). The pulsing electric fields enhanced the mobility of the charged particles in the fouling layer and decreased the electric resistance of the electrodialysis cell. It was clearly observed that the pulsing electric fields with different frequencies reduced the fouling potentials, and consequently the power consumption was reduced significantly as a fouling mitigation method.     

Fouling mitigation in the repeated batch runs of electrodialysis with humate foulant

Since membrane fouling is one of the important considerations in electrodialysis, many approaches have been considered in order to minimize fouling of the process. In this study, square wave powers having pulsing effects were employed to investigate the effects of the frequencies on the fouling mitigation during fouling experiments of humate, forming a loosely packed fouling layer on the anion exchange membrane surface. It was shown that a pulsing electric field with determined optimal frequency reduced the fouling potential of an already fouled system in repeated batch runs at a significant level. It was suggested through electrodialysis experiments of humate that the pulsation of the electric field affected the electromigration of the charged particles deposited in the fouling layer, thus decreasing fouling potentials.     

Membrane fouling in electrodialysis: a model and experiments

Membrane fouling is a common cause for poor performance in electrodialysis systems, usually because it reduces the limiting current. Fouling may be caused by deposits of either neutral matter or colloidal matter with ion exchange properties. In the present paper a model for membrane fouling is developed and expressions are derived for the reduction in limiting current caused by both neutral fouling films and films having ion exchange properties. The effect of fouling is shown to depend not only on the properties of the fouling film, but also on the hydrodynamic conditions in the channels and in the case of ion exchange fouling films on the salt concentration in the dialysate channel. Ion exchange fouling films are shown to be much more effective in reducing the limiting current than neutral films. Some experimental data are presented which confirm the trend of the theory for fouling with ion exchange films.     

Removal of hardness in fermentation broth by electrodialysis

Lysine fermentation broth was desalinated by electrodialysis to reduce hardness concentrations as a pretreatment procedure for the purification and recovery of amino acids. Electrodialysis performance was investigated in terms of the rate of reduction in conductivity in dilute solutions and electrodialysis cell resistance for different ion exchange membranes at a constant current density. Among the membranes investigated in this study, membranes with high water content showed the better performance for hardness removal. Fouling experiments revealed that organics gave rise to fouling effects on the anion exchange membrane during demineralization of the lysine fermentation broth. The pulsed electric field with the half‐wave power enhanced the electrodialysis performances by mitigating membrane fouling in desalination of the lysine fermentation broth. This study successfully demonstrated the potential use of pulse power as an effective cleaning‐in‐place (CIP) method during electrodialysis of fermentation broth. © 2002 Society of Chemical Industry     

The effect of oilfield polymer-flooding wastewater on anion-exchange membrane performance

Polymer-flooding process is one of tertiary oil extraction technologies. It has stepped into industrialization application period in Daqing Oilfield (China) in recent years. It plays an increasingly important role in the oil exploitation, but around 60 million ton polymer-flooding wastewater is produced per day with oil extraction together. Therefore, the treatment and reuse of wastewater becomes very significant. Experiments show that the polymer-flooding wastewater can replace freshwater to be reused to confect polymer solution after removing total dissolved solids (TDS) by electrodialysis technology. This treatment technology can not only decrease environmental pollution resulted by wastewater discharge, but also achieve closed-circuit of polymer-flooding wastewater during crude oil extraction. It has significant effect for protecting environment and saving water resource. After carrying out lots of experiments in the lab, the pilot-test electrodialysis operation has been applied to treating polymer-flooding wastewater and received better economic effect. But serious ion-exchange membrane fouling (especially for anion membrane) is the main problem that holds back this technology's further application. The emphasis of this research is to study the effect of polymer-flooding wastewater on anion membrane performance. Oilfield wastewater is a kind of multiphase system that containing solid suspend, liquid suspend, and dissolved salt. A small-scale 5-compartment electrodialysis was developed to study the effect of main fouling substances of polymer-flooding wastewater (solid suspension, crude oil and polymer) on the performance and apparent characteristics of anion membrane from microcosmic (membrane surface resistance, average current, desalination rate, etc.) and macroscopical (scanning electron microscope and atomic force microscope, AFM) views, respectively. The concentration of cations is measured with atom absorbing spectrum (PERKIN-ELMER 703), the concentration of anions is measured with ion chromatogram (DLONEX 4500i) and the sum amount of ionic concentration is TDS. The experimental results show that fractional solid suspension congregated on the surface of, or inside, anion membrane and fouled membrane. Crude oil formed a compact oil film after being absorbed, which affects ions to get through ion-exchange membrane. The polymer may congregate on the surface of anion membrane, and had some influence for permeation of anion membrane. The membrane fouling changes little with time going on.     

Macroreticular anion exchange membranes for electrodialysis in the presence of surface water foulants

In this work two new types of anion exchange membranes having pore sizes of macro dimensions are described. Static and dynamic fouling resistance to common large anions found in surface waters is evaluated. Improvements over conventional microporous anion membrane types are discussed with respect to electrodialysis.