双极膜的制备

在双极膜制备中，通过添加适当的催化介质如多级胺类，金属氧化物和氢氧化物可有效的改善双极膜的性能。在本研究工作中通过添加催化介质和控制双极膜介面层清析度，制得性能良好的双极膜。工作电压在１００ｍＡ／ｃｍ＾２时，用１．０Ｎ ＮａＳＯ４测试膜电压降为１．５￣２．５Ｖ。     

纳米SiO2改性海藻酸钠/壳聚糖双极膜的制备与表征

在壳聚糖(CS)阴离子交换膜层中添加纳米SiO2,制备了PVA-SA/SiO2-CS双极膜(其中,PVA:聚乙烯醇;SA:海藻酸钠),并用扫描电镜、热重、电子万能试验机、接触角测定仪、J-V关系和交流阻抗谱等对其进行了表征。研究结果表明,双极膜经纳米SiO2改性后,亲水性得以提高,壳聚糖膜的接触角从104.01°下降到78.39°。膜亲水性的提高增强了膜与水分子间的作用,减弱了水的键合力,促进了中间界面层水的解离,降低了双极膜电阻压降(IR降)和槽电压,当电流密度为45 mA.cm.2时,槽电压从9.0 V下降到6.2 V。此外,添加纳米SiO2还可提高双极膜热稳定性和机械性能,双极膜的断裂伸长率从81.29%提高到87.67%,杨氏模量从30.68 MPa提高到79.59 MPa。     

双极膜和水电渗离解过程简介

本文介绍了双极膜（ＢＰＭ）和水电渗离解（ＥＨ）的一些基本知识，包括对双极膜的要求，ＥＨ的工艺过程，膜堆，主要工艺参数和应用范围等，同时指出了双极膜技术在酸，碱生产，ｐＨ调节，无机物和有机物制备以及废水治理和回用等领域应用的优越性。     

纳米二氧化钛-氧化锌改性双极膜制备与表征

在壳聚糖(CS)阴离子交换膜层中添加纳米二氧化钛-氧化锌复合半导体材料,制备了PVA-SA/TiO2-ZnO-CS双极膜(其中:PVA为聚乙烯醇;SA为海藻酸钠),并用热重分析等对其进行了表征。研究结果表明,纳米二氧化钛-氧化锌复合半导体材料较纳米氧化锌或纳米二氧化钛单一半导体材料具有更强的光催化双极膜中间界面层水解离能力,能大大降低双极膜的膜阻抗和膜电阻压降(IR降)。当电流密度为60 mA/cm2时,在高压汞灯照射下,PVA-SA/TiO2-ZnO-CS双极膜的槽电压较没有高压汞灯照射时下降了1.0 V;而PVA-SA/TiO2-CS双极膜和PVA-SA/ZnO-CS双极膜仅分别下降了0.7 V和0.6 V。此外,添加纳米二氧化钛-氧化锌复合半导体材料可提高双极膜的亲水性、热稳定性和机械性能。     

双极膜制酸制碱电流效率的测定

双极膜制酸碱的电流效率是反映双极膜性能的重要参数，它主要取决于双极膜阴，阳膜层对离子的选择性。本文设计了测试双极膜阴、阳膜层对离子的选择性和制酸制碱电流效率的简单、可靠方法，并用该方法完成了自制双极膜和上海产异相双极膜电流效率的测试实验。     

具有不同取代基数量铁酞菁衍生物改性双极膜的性能研究

分别用具有不同取代基数量铁酞菁衍生物加入羧甲基纤维素钠(CMC)阳离子交换膜中,制备改性的CMC/CS双极膜(BPM,CS∶壳聚糖)。结果表明,经铁酞菁改性后,阳膜的离子交换容量、亲水性和双极膜的机械性能均获得提高,双极膜的溶胀度下降。此外,改性后,铁酞菁衍生物可在双极膜中间界面层形成高荷电区,促进水解离,降低膜阻抗和槽电压。当电流密度为60 mA/cm2时,Fe2Pc2(COONa)12-CMC/CS BPM,FePc(COONa)8-C MC/CS BPM,FePc(COONa)4-CMC/CS BPM和CMC/CS BPM的膜电压分别为5.6,6.2,6.5,8.9 V。     

离子膜氯碱电解槽电压的影响因素

引言离子交换膜（ＩＥＭ）氯碱电解槽的槽电压是考核氯碱装置运行性能的一个重要指标,槽电压的高低直接影响到氯碱产品的成本及其市场竞争力。电解槽硬件、电解液和膜是影响槽电压的主要可控制因素,就这些因素对槽电压的影响程度进行概要分析。１电槽硬件的影响１１阳...     

双极膜制酸碱的实验

本文报导了自制双极膜的工作性能，利用双极膜水解离效应将盐转化成相应的酸和碱，对此工艺及操作方式进行了探索，研究了各种工艺参数如电流密度，膜电压降、电流效率之间的关系。     

电去离子过程的实验研究

通过对反渗透后接电去离子过程的实验研究,考察了不同操作条件对ＥＤＩ过程产水水质的影响,探讨了ＥＤＩ过程去的最佳操作参数,同时还考察了ＥＤＩ产水过程的稳定性。实验表明,ＥＤＩ过程可以长时间连续运行,并能获得高质量的纯水。同时还发现,提高ＥＤＩ膜堆的操作电流可以得到高质量的纯水;进入ＥＤＩ膜堆的原水电导率越低,ＥＤＩ的产水水质就越好;适当提高ＥＤＩ膜堆水回收率可以得到纯度较高的产水;适当提高ＥＤＩ原水     

纳米Fe~(3+)-TiO_2改性双极膜的制备、表征及其在海水中一、二价阳离子分离的应用

采用溶胶-凝胶法制备了Fe3+掺杂TiO2光催化剂。分析表明,制备的Fe3+-TiO2为锐钛矿型,其禁带宽度低于TiO2。将Fe3+-TiO2添加到聚乙烯醇-壳聚糖(PVA-CS)阴离子交换膜中,制备了PVA-CMC/Fe3+-TiO2-PVA-CS双极膜(BPM),(CMC:羧甲基纤维素钠)。研究结果表明,Fe3+-TiO2较TiO2具有更强的光催化双极膜中间界面层水解离能力,在太阳光照射下能大大提高水解离效率,降低双极膜膜阻抗和跨膜电压降。当电流密度为60 mA·cm-2时,PVA-CMC/Fe3+-TiO2-PVA-CS双极膜槽电压下降了0.8 V。此外,通过Fe3+-TiO2改性,CS膜亲水性和双极膜机械性能均获得提高。将改性后的双极膜用于分离模拟海水中一、二价阳离子,在太阳光照射下,K+离子和Na+离子双极膜透过率较无光照时有明显提高,电渗析2 h,K+离子和Na+离子的透过率分别为90.31%和82.93%,而二价阳离子的透过率均小于1.0%。     

影响双极膜电学性能的几个关键问题的讨论

从化学动力学角度讨论了双极膜中间层催化剂的选择,双极膜中间层水的补充问题是双极膜的性能至关重要,导出阴阳膜匹配的阻抗公式,说明其电阻不是简单的阴阳膜电阻之和。     

Preparation of bipolar membranes. II

The bipolar multilayer membrane was prepared by a new technique. The interfacial layer and cation layer were formed by only one step. The anion and cation layers were made from the same material from which chloromethylated polysulfone was used as a basic material. The bipolar membranes were composed of a solvent‐resistant anion layer with crosslinking matrix by the reaction of chloromethylated polysulfone in DMF with diamine; an ultrathin interfacial layer from chloromethylated polysulfone solution in DMF, containing cation‐exchange resin and both quaternary and nonquaternary amine groups; and a cation layer from chloromethylated polysulfone dispersing cation resin powder. The prepared bipolar membrane exhibits a lower voltage drop over 100 mA/cm² and stable performances at a long‐term operation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1733–1738, 2001     

A simple model to determine the trends of electric-field-enhanced water dissociation in a bipolar membrane. II. Consideration of water electrotransport and monolayer asymmetry

This work elucidates the mechanism of electric-field-enhanced water dissociation. Particular attention has been given to the influences of water electrotransport and monolayer asymmetry on the water dissociation process. A simple model was proposed with consideration of these two factors and mathematically analyzed in term of thickness ratio, fixed group concentration ratio and water diffusivity ratio of the anion selective layer to the cation selective layer on typical current density curves of bipolar membranes. The results suggest that for practical applications, an asymmetric bipolar membrane with proper ion-exchange capacity and high permeability to water is more effective than a symmetric one. Theoretical simulation values were compared with both the theoretically calculated data by a model without consideration of water electrotransport and the experimental current voltage curves. It is shown that the calculated potential across a bipolar membrane is higher at given current density, which permits a more precise prediction of experimental I–V curves for the case of a bipolar membrane with high water permeability. However, for a bipolar membrane with poorer water permeability, it seems that the calculated value with the model without consideration of water electrotransport is closer to the experimental values, but the model with consideration of water electrotransport can effectively predict the over-limiting current density.     

Preparation of bipolar membranes (I)

The bipolar membranes were prepared by charged material of polysulfone as a base. The bipolar membranes were composed of a solvent‐resistant anion exchange layer with a crosslinking matrix prepared by the reaction of chloromethylated polysulfone in DMF with diamine, an interfacial layer made from chloromethylated polysulfone solution in DMF containing cation exchange resin and amine, and a cation exchange layer made from sulfonated polysulfone dispersing cation resin powder. The prepared bipolar membrane can exhibit lower voltage drop over 100 mA/cm². The critical requirement for producing bipolar membranes of low potential drop is the creation of a thin interfacial region with a low electrical resistance and a suitable chemical structure, which act to catalyze water splitting. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1658–1663, 2001     

Modelling the mode of operation of PEMFC electrodes at the particle level: influence of ohmic drop within the active layer on electrode performance

Numerical modelling of charge transfer using the finite element method within the whole active layer of proton exchange membrane fuel cell (PEMFC) electrodes is proposed in order to study the electrocatalyst utilization as characterized by the effectiveness factor. In this way, two modified approaches based on the thin film and agglomerate models are developed for studying ionic ohmic drop effects in the active layer at both the electrolyte layer and electrocatalyst particles scales. The catalyst phase is considered to be a network of spherical nanoparticles instead of the classical representation as a uniform distribution over a surface (thin film model) or in a volume (agglomerate model). Simulations point out unexpected effects at the local level due to the discrete distribution of the catalyst phase as nanoparticles. Finally, the results are applied to the practical case of oxygen reduction and hydrogen oxidation.     

Application of Ni-free high nitrogen stainless steel for bipolar plates of proton exchange membrane fuel cells

Ni-free 23Cr-1N stainless steel was examined as bipolar plates for proton exchange membrane fuel cells. Corrosion resistance of the 23Cr-1N stainless steel was better relative to 22Cr stainless steel in the simulated cathodic environments. As confirmed by X-ray photoelectron spectroscopy, the polarized 22Cr and 23Cr-1N stainless steels at pH 2.3 presented predominantly chromium oxide in the outer passive layers. At pH 4.3, the passive layer of the polarized 22Cr stainless steel changed to iron oxides dominant. Interestingly, on the other hand, the polarized 23Cr-1N stainless steel preserved chromium oxide rich outer passive layer, which provides good corrosion resistance. As a result, although the initial cell voltage was slightly lower (∼40 mV), the 23Cr-1N stainless steel bipolar plates employing cell showed better cell voltage stability up to 1000 h, compared with the 22Cr stainless steel employing cell. The operation voltage became further higher through a surface modification of the 23Cr-1N stainless steel with TiN nanoparticles. It seems that the corrosion resistive Ni-free 23Cr-1N is possible to apply for bipolar plates of proton exchange membrane fuel cells.     

光催化双极膜的制备及应用

以聚乙烯醇（PVA）和羧甲基纤维素钠（CMC）混合制成阳膜层材料,以聚乙烯醇和壳聚糖（CS）混合制成阴膜层材料。分别用氯化铬、戊二醛对阳膜、阴膜进行交联改性,并在阴阳膜层间加入具有光催化活性的纳米二氧化钛,得mCMC/TiO2/mCS双极膜。该双极膜在紫外光照射下,具有高的水解离效率,优良的亲水性能,双极膜阻抗小,工作电压低,并将该膜应用于合成乙醛酸和丁二酸体系中。     

电场增强条件下双极膜水解离的简化模型

This work is concentrated on elucidating the mechanism of the electric field enhanced water dissociation.A simple model was established for the theoretical current-voltage characteristics in water dissociation process on a bipolar membrane based on the existence of a depletion layer and Onsager‘s theory. Particular attention was given to the influence of applied voltage on depletion thickness and the dissociation constant. The factors on the water splitting process, such as water ditfusivity, water content, ion exchange capacity, temperature, relative permittivity,etc. were adequately analysed based on the derived model equations and several suggestions were proposed for decreasing the applied voltage in practical operation. The water dissociation tests were conducted and compared with both the theoretical calculation and the measured current-voltage curves reported in the literature, which showed a very good prediction to practical current-voltage behavior of a bipolar membrane at high current densities when the splitting of water actually commenced.     

双极膜制备及改性研究进展

双极膜作为一种新型复合离子交换膜,以其独特的优点,为化工、环境科学和能源利用等领域中存在已久的诸多技术难题提供了新的思路和解决办法。目前,国内外关于双极膜的研究主要集中于通过对膜材料和中间层的改性以促进双极膜的水解离,提高双极膜离子交换能力和降低能耗等方面。本文介绍了热压成型法、黏合成型法、流延成型法,含浸法等双极膜制备方法的原理、特点、应用实例和新进展,并对比分析了各种方法的优势和存在的不足。同时,从膜材料改性和中间层改性两个方面对近年来双极膜的改性研究进行了重点讨论。最后指出,国内多数双极膜的制备仍处于实验研究阶段,将接枝、共混、离子辐射等膜材料改性方法应用于双极膜的制备中,同时寻找亲水性好、耐高温性能好的基膜材料将是双极膜制备领域的重要方向。     

Properties of a cation-exchange membrane adsorbed or ion-exchanged with hexadecylpyridinium chloride

Some electrochemical properties of a cation-exchange membrane that had been adsorbed or ion-exchanged with hexadecylpyridinium chloride were observed. Two observations were made: (1) current/voltage curves (2) electric resistance of the membrane during the electrodialysis, and current efficiency of cations.Adsorption of or ion-exchange with hexadecylpyridinium chloride was carried out by immersion of the membrane in an aqueous solution of hexadecylpyridinium chloride for a given period.As the period of immersion of the membrane in the solution of hexadecylpyridinium chloride increased, the voltage of current/voltage curves remarkably increased at low cd. The current/voltage curve of the membrane immersed more than 16 h was different from that immersed less than 16 h. When the membrane which had been adsorbed or ion-exchanged with hexadecylpyridinium chloride was used in electrodialysis, the electric resistance of the membrane increased remarkably, and showed a maximum value during the electrodialysis as the immersion period increased. These phenomena are attributable to the transformation of the cation-exchange membrane to the bipolar type ion-exchange membrane and then the transformation of the bipolar type to the amphoteric type because hexadecylpyridinium ion, in the membrane's structure, functions as fixed ion-exchange group.