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     

Use of bipolar membranes for ion exchange resin regenerant production

The utilisation of electrodialysis bipolar membranes to prepare hydrochloric acid and sodium hydroxide from a sodium chloride solution was tested at West Thurrock Power Station. The product chemicals were then used to regenerate full scale ion exchange units on the site and the results compared to normal operation with commercial regenerants. The large scale pilot plant was found to operate satisfactorily and the quality of produced chemicals was in line with predictions. The adoption of on-site, on-demand production of regenerants could offer immediate advantages for remote installations which would otherwise be dependent on the transport of dangerous chemicals over long distances. In the longer term further advances in the selectivity of commercially available membranes and the prevailing cost of commercial regenerants are considered the key factors governing the future rate of implementation of this novel process.     

BPM2型双极膜电渗析装置的研制

目前国内能正式应用的双极膜电渗析装置比较缺乏,根据双极膜装置的特点与要求,参考国内外先进的电渗析装置的有关技术,研制出适合双极膜电渗析过程的装置.该装置具有耐腐蚀(耐强酸、强碱、有机溶剂)、膜堆体积小(隔板厚度为0.6mm),有效膜面积比率大、密封效果好、防漏电,防内漏、阻力小、电流效率高、使用寿命长、可以多次反复拆装等特点.本文介绍了装置的主要构成、特性及测试情况,并对几种典型的双极膜过程进行陛能测试,发现其各种性能比文献报道的装置均有所改进,从而为我国双极膜的推广应用提供成型的装置以及为理论研究提供研究平台.     

双极膜电渗析技术的研究进展

双极膜电渗析技术(BMED)是利用直流电场作用下双极膜界面层内发生水解离生成H+和OH-这一电化学特性,通过将双极膜与阴、阳离子交换膜适当组合,可实现不同的特种分离功能。与传统工艺相比,BMED具有高效节能、环境友好、操作便捷等突出技术优势。本文介绍了3种不同的BMED工作模型以及BMED在有机酸生产、水除盐、蛋白分离、超纯水制备等领域的最新研究进展,对BMED技术的进一步研究与发展进行了展望。     

Extraction of amphoteric amino acids by an electromembrane process. pH and electrical state control by electrodialysis with bipolar membranes

Electrodialysis (ED) with bipolar membranes (BPM) was applied for the extraction of amino acids in an electrically neutral form. Under voltage, BPM split water, generating hydroxyl ions at the anodic side and protons at the cathodic side. The use of these membranes represents a newer method to convert neutral species into electrically charged species that are able to cross homopolar ED membranes. The ED operations were performed using a laboratory cell with a membrane area of 50 cm². A mixture containing five amino acids (Gly, Ser, Ala, Val, Phe) was examined. The concentration of each amino acid was 100 mmol dm⁻³. The current density and pH in the feed and receiver compartments were varied. Extraction degrees and current efficiencies were calculated and compared under different experimental conditions. © 1998 Society of Chemical Industry     

含哌啶阳离子侧长链型一/二价阴离子选择性分离膜的制备

基于超酸催化聚合机理制备了含咔唑片段的聚合物主链结构,并通过调控季铵化反应中N-甲基哌啶单体的用量,得到了不同哌啶离子含量的阴离子选择性分离膜。通过核磁共振氢谱证明了聚合反应和季铵化反应顺利进行。热重和动态机械分析的测试结果表明膜具有优异的热稳定性和力学性能。通过电渗析 （ED） 测试膜的阴离子分离性能,结果显示离子通量和选择性均优于商业膜Neosepta ACS。在NaCl/Na₂SO₄体系中,QPC-Pip-60的Cl^-通量可达3.24 mol·m^-2·h^-1,选择性可达11.6。在NaOH/Na₂WO₄碱回收体系下,良好的微相分离结构使得OH^-通量可达3.59 mol·m^-2·h^-1,选择性最高为70。长时间稳定性测试和碱稳定性测试结果表明所制备的系列膜具有优异的循环稳定性和耐碱性能。     

含哌啶阳离子侧长链型一/二价阴离子选择性分离膜的制备

基于超酸催化聚合机理制备了含咔唑片段的聚合物主链结构,并通过调控季铵化反应中N-甲基哌啶单体的用量,得到了不同哌啶离子含量的阴离子选择性分离膜。通过核磁共振氢谱证明了聚合反应和季铵化反应顺利进行。热重和动态机械分析的测试结果表明膜具有优异的热稳定性和力学性能。通过电渗析 （ED） 测试膜的阴离子分离性能,结果显示离子通量和选择性均优于商业膜Neosepta ACS。在NaCl/Na₂SO₄体系中,QPC-Pip-60的Cl^-通量可达3.24 mol·m^-2·h^-1,选择性可达11.6。在NaOH/Na₂WO₄碱回收体系下,良好的微相分离结构使得OH^-通量可达3.59 mol·m^-2·h^-1,选择性最高为70。长时间稳定性测试和碱稳定性测试结果表明所制备的系列膜具有优异的循环稳定性和耐碱性能。     

双极膜电渗析法制备1,5-戊二胺

1,5-戊二胺(C5H14N2)是生物法制备尼龙材料的重要原料,具有广泛应用前景。利用双极膜电渗析产碱技术可将盐溶液中的1,5-戊二胺盐转换为1,5-戊二胺,实现生物发酵液中1,5-戊二胺的无害化提取过程。本工作用1,5-戊二胺硫酸盐模拟生物发酵液的主要成分,探究了不同电流模式、电流密度、盐室初始浓度及杂质离子对1,5-戊二胺制备过程指标产生的影响,分析了双极膜在长时间运行后膜表面的损伤和污染情况。结果表明,料液中的硫酸根离子可以有效地被分离,在电流为3.6 A的恒流模式下,1,5-戊二胺回收率可达到97.5%以上;在电压为29 V的恒压模式下,1,5-戊二胺回收率可达到90%以上。高至3.45 kWh/kg双极膜在反复使用35次左右后,其阳离子交换层表面出现损伤的迹象,阴离子交换层表面黏附微量固体污染物。     

Electrodialytic transport properties of heterogeneous cation‐exchange membranes prepared by gelation and solvent evaporation methods

The heterogeneous cation‐exchange membranes were prepared by employing two different methods: immersing the cation‐exchange resin‐loaded membranes in gelation bath; evaporating the solvent upon casting a uniform solution of cation‐exchange resin on a glass plate. The effect of resin loading on the electrochemical properties of the membranes was evaluated. The permselectivity of these heterogeneous membranes and transport number of calcium ions relative to sodium ions was evaluated with respect to the extent of resin loading and the methods of preparation. It is found that the membrane potential, transport number, permselectivity, and relative transport number are prominently high in the solvent evaporation method compared with the gelation method. The transport number of calcium ions relative to sodium ions in the solvent evaporation method increased monotonously with increasing resin loading. However, the increase of resin loading did not influence much on the relative transport numbers in the gelation method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 198–207, 2006     

Characterization of cation‐exchange membrane fouling during bipolar membrane electrodialysis of monosodium glutamate isoelectric supernatant

BACKGROUND: A novel procedure that involved regeneration and recycling of ammonia and sulfuric acid from monosodium glutamate isoelectric supernatant with bipolar membrane electrodialysis (BMED) was proposed. As the performance of the membranes deteriorated during the batch runs, fouling of the cation‐exchange membrane (CEM) in contact with the base cell was studied. RESULTS: During ten consecutive batches of BMED, some operating parameters deteriorated gradually. Using scanning electron microscopy observations, fouling deposits were found on the CEM surface on the base cell side. Using Fourier transform infrared spectroscopy and reversed‐phase high‐performance liquid chromatography (RP‐HPLC), the organic fouling fraction of the CEM foulants was found to contain eight amino acids. Using X‐ray energy‐dispersive analysis, the mineral fouling fraction was shown to be mainly O and Ca elements, and a little Mg. Using X‐ray diffraction, the inorganic foulant was identified as CaCO₃, mainly in the form of calcite and a little aragonite. CONCLUSION: The CEM was subject to membrane fouling consisting of an organic fouling fraction and a mineral fraction. The organic fraction occurred as ions with some positive charges from the isoelectric supernatant and probably existed in the form of amino acids or their peptides. The mineral fraction was mainly CaCO₃ calcite and aragonite, and probably a little amorphous Ca and Mg hydroxides. Copyright © 2011 Society of Chemical Industry     

Structural effects of ion‐exchange membrane on the separation of L‐phenylalanine (L‐Phe) from fermentation broth using electrodialysis

The effects of membrane structure on the separation of L ‐phenylalanine (L ‐Phe) by electrodialysis from a fermentation broth and on the fouling tendency were investigated in this study. Two anion‐exchange membranes (Neosepta AFX and AM‐1, Tokuyama, Japan) were selected and characterized using the chronopotentiometry method. For a fresh membrane, AFX showed a lower electrical resistance and a lower permselectivity than AM‐1. After being fouled with humic acid, however, the electrical resistance of AFX was higher than that of AM‐1. The L ‐Phe selectivities for both membranes were lower than those of the fresh membranes. The result may be attributed to the structural difference between AFX and AM‐1 membranes. AFX has a lower repulsion force against the co‐ion and could be more strongly affected by the foulants than AM‐1 because AFX has a more porous structure than AM‐1. Experiments on the separation of L ‐Phe from the fermentation broth were carried out using two different stack configurations, ie desalting electrodialysis and water‐splitting electrodialysis. It was observed that the recovery efficiency of L ‐Phe through electrodialysis for 100 min reached 95% for AFX and 85% for AM‐1. In the desalting configuration of electrodialysis, the solution pH must be adjusted to alkaline conditions to recover the L ‐Phe through the anion‐exchange membrane. On the contrary, it was possible to recover the L ‐Phe without adjustment of the solution pH in the water‐splitting electrodialysis because OH^? generated from the bipolar membrane converted neutral L ‐Phe into an anion. © 2002 Society of Chemical Industry     

Pervaporation separation of water/ethanol mixture using asymmetric ion‐exchange membranes containing aluminum ions

The asymmetric aluminum ion exchange polysulfone membranes have successfully been prepared for the dehydration of ethanol‐water mixture. The relationship between the membrane morphology, separation performance, and the ion content of membranes were discussed in this study. The experimental results showed that the separation performance of those membranes was increased upon increasing the degree of aluminum ion exchange in polysulfone membranes. Both permeation rate and separation factors of those membranes increased with increasing the degree of ion exchange. The increase in separation performance of aluminum ion exchange membranes was mainly attributed to ion crosslinking in polymer network and the hydration effects of exchanged ion in membranes. On the other hand, the operating temperature in the PV process showed a significant influence on the dehydration of water molecules in the permeate. An increase in temperature increased the permeation flux of permeate but slightly decreased its selectivity. The aluminum asymmetric ions in membranes showed a strong influence on permselectivity of asymmetric ion exchange membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

双极性膜电渗析技术在亚氨基二乙酸制备中的应用

报道了双极性膜电渗析取代现行工艺中亚氨基二乙酸钠转化成亚氨基二乙酸的酸化过程的研究。亚氨基二乙酸钠的转化率达 99 2 % ,亚氨基二乙酸钠溶液转化的收率达 98 5 % ,平均电流效率达 75 % ,平均耗电低于 0 80kW·h/kg亚氨基二乙酸 ,制得的亚氨基二乙酸产品的纯度≥ 99% ,达到或超过进口亚氨基二乙酸产品的质量要求     

双极膜电渗析处理生物质水解液的过程性能研究

在由双极膜和阴离子交换膜组成的两室双极膜电渗析装置中,研究了生物质水解液糖、酸分离和酸回收的过程性能。考察了不同膜对、进料浓度、电流密度、处理室循环流量及操作温度等因素对于处理水解液过程中的电流效率和平均功耗的影响。结果表明,由BP-1双极膜与A501SB阴离子交换膜组成的膜对的性能最佳;过程的电流效率随进料液酸浓度的增大而下降,过高酸浓度的水解液进料对电渗析分离过程不利;较高操作电流密度条件下电流效率高,利于降低功耗,本装置的处理室适宜循环流量为30.0 mL/m in;操作温度的升高,对提高电流效率作用不明显,但利于降低平均功耗,本实验装置的合适操作温度为35℃。     

Transport of Cu(II) ions through charged cation‐exchange membranes

Transport of Cu(II) ions through polysulfonated cation‐exchange membranes under Donnan dialysis conditions was studied as a function of the pH gradient. The used charged membranes are homogeneous (polysulfone composition) and heterogeneous (polysulfone with polyester support) structures which are strongly acidic cation‐exchange microporous‐type membranes. The flux increases with decreasing of the pH gradient, which is influenced by the transport of copper ions. The quantitative relations were obtained which describe the time dependence of the transport system with the equilibrium distribution and the results were correlated with the flux data as well as with the membrane structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 421–427, 2001     

Preparation and characterization of bipolar membranes modified using photocatalyst nano‐TiO2 and nano‐ZnO

The nano‐ZnO and nano‐TiO₂ were added into chitosan (CS) anion layer to prepare polyvinyl alcohol (PVA) ‐ sodium alginate (SA)/ TiO₂‐ZnO‐CS (here, PVA:polyvinyl alcohol; SA:sodium alginate) bipolar membrane (BPM), which was characterized using scanning electron microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TG), electric universal testing machine, contact angle measurer, and so on. Experimental results showed that nano‐TiO₂‐ZnO exhibited better photocatalytic property for water splitting at the interlayer of BPM than nano‐TiO₂ or nano‐ZnO. The membrane impedance and voltage drop (IR drop) of the BPM were obviously decreased under the irradiation of high‐pressure mercury lamps. At a current density of 60 mA/cm², the cell voltage of PVA‐SA/TiO₂‐ZnO‐CS BPM‐equipped cell decreased by 1.0 V. And the cell voltages of PVA‐SA/TiO₂‐CS BPM‐equipped cell and PVA‐SA/ZnO‐CS BPM‐equipped cell were only reduced by 0.7 and 0.6 V, respectively. Furthermore, the hydrophilicity, thermal stability, and mechanical properties of the modified BPM were increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

电渗析技术研究现状与进展

简述了电渗析技术的几种类型,并对电渗析技术在水处理、食品和化工方面应用的研究现状和发展前景进行了综述。     

Nitric acid and sodium hydroxide generation by electrodialysis using bipolar membranes

An electrodialysis process with bipolar membranes was used to generate HNO3 and NaOH from NaNO3 which can be found in industrial waste waters. The current efficiency of this process is limited by proton leakage through the anion exchange membrane (AEM), co-ion leakage through bipolar membranes (BPM) and water transport through the ion exchange membranes. Three cell configurations using three or two compartment cells with different anion or cation exchange membranes (CEM) in stack series were used and compared. Electrodialysis with three compartments gives the best current efficiencies for nitric acid and sodium hydroxide production from sodium nitrate.     

双极膜电渗析技术在工业高含盐废水中的应用

双极膜电渗析（BMED）作为新型膜分离技术,可将盐转变为相应的酸和碱,围绕BMED技术在工业高含盐废水领域的应用已逐渐成为热点,但在实际应用中还存在一些亟需解决的难点。本文主要介绍了近年来BMED技术在处理工业高含盐废水领域的研究现状,提出和探讨了限制BMED技术在该领域大规模工业化应用的3个关键性问题,即与酸碱浓度和纯度有关的技术问题、与过程成本有关的技术经济性问题以及与投资成本有关的经济性问题。针对这3个问题,指出BMED技术未来发展方向应致力于降低双极膜成本,减弱或消除离子交换膜同离子泄漏及水迁移过程。对于现阶段而言,将制备的酸碱回用于系统内部,是解决酸碱品质较低而未能商品化的主要途径,同时该过程可节省酸碱外购费用,弥补BMED技术投资成本过高问题。     

Polyurethane and carboxylated polysulfone blend ultrafiltration membranes. I. Preparation and characterization

Polysulfone was functionalized by carboxylation and blended with polyurethane (ether type). Blend membranes were prepared in the presence and absence of the additive poly(ethylene glycol) 600 and subjected to ultrafiltration characterizations such as compaction, pure water flux, water content, and hydraulic resistance. Morphological studies of the membranes were performed with scanning electron microscopy. The effects of the polymer composition and additive concentrations on the above parameters were analyzed and the results compared. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1307–1315, 2005