电渗析用于1,3-丙二醇发酵液脱盐的实验研究

发酵法生产1,3-丙二醇时产生的有机酸盐会对1,3-丙二醇产品的后续提取造成很大困难,尝试采用电渗析方法解决这一问题,并考察了操作电压、淡室流速、浓室初始浓度等操作条件对脱盐效果的影响．实验研究表明,电渗析技术可以有效脱除1,3-丙二醇发酵液中存在的有机酸盐,较好地解决1,3-丙二醇后提取中存在的问题,同时由扩散引起的1.3-丙二醇产品损失率不高于6．0％．经絮凝处理后采用该方法连续脱盐100h发现,发酵液中残存的菌体会对离子膜造成一定污染．     

双极膜电渗析法1,3-丙二醇发酵液的脱盐处理及主要副产物的回收

在前期研究的基础上,使用双极膜电渗析系统(简称BMED)脱除1,3-丙二醇(PDO)发酵液中的有机盐和无机盐,脱盐率达到99％o以上时,单批次过程能耗为21.9 (W· h)/L发酵液,PDO回收率为96.1％.在此实验基础上进行了七个批次连续脱盐操作.实验结果表明,BMED受连续脱盐操作影响不大,每个批次PDO回收率在92.7％～96.8％之间;七个批次中,每升发酵液脱盐所需的总能耗从21.7W·h增加到了31.6W·h.此外,本实验中得到的碱室液经浓缩后被用于3L和5L的1,3-丙二醇发酵罐的pH调节,酸室液的主要成分丁二酸也被成功结晶回收.     

建议把"离子交换膜"正名为"离子电迁移膜"

1 电驱动膜过程和离子电迁移膜名称的由来 上世纪50年代用粉状离子交换树脂和粘结剂制成片状,用它制成电渗析装置,作电解质溶液的脱盐和浓缩,该膜称为离子交换膜.随着离子交换膜和电渗析技术的进一步发展,该膜的应用扩大到化工生产和三废治理等领域.     

均相离子交换膜的电渗析水迁移性能研究

在电渗析浓缩盐水实验的基础上,利用电渗析数学模型,分析浓缩实验中的离子迁移和水迁移过程.评价了A、B两种新型均相离子交换膜的性能差异,测定其电渗水迁移系数基本相等,为12.20 mol水/mol盐左右;浓渗水迁移系数相差较大,B型膜为21.56 g/(m~2·h·MPa),A型膜则为30.15 g/(m~2·h·MPa),是B型膜的1.4倍.利用模型对浓缩过程进行水渗分析,结果表明,实验前期,浓缩过程中的水以电渗水迁移为主,实验后期则以浓渗水迁移为主;水迁移系数越大,最终的浓缩液浓度越低,选择水迁移系数小的离子交换膜可有效提高盐水的浓缩效率.在工业应用方面,浓渗系数较小的B型膜主要用于浓缩过程,A型膜则可应用于脱盐过程.     

新型通用离子交换膜的研究与实践

基于离子交换膜的电膜技术,由于其独特的离子传递特性,可以进行离子物系的分离分级,在清洁生产、节能减排、环境保护、能量转换等方面有着广泛的应用前景。然而,目前国内相关均相离子膜产品尚处于起步阶段,以日本为首的国家对我国进行相关技术封锁和价格垄断。正是基于这样的产业背景和现实意义,开发出新型的均相离子膜制备路线尤为重要。本课题组提出了一种简单而通用的侧链型离子化芳香族聚合物的合成方法,即“离子单体聚酰基化”均相离子交换膜制备路线,并通过ATRP法来设计离子交换膜的主链憎水、侧链亲水的接枝结构,通过对接枝密度和接枝长度进行调节,实现对膜性能的调控,以满足不同的应用过程对膜性能的要求。此种均相离子交换膜的制备工艺及产业化生产攻关,可以打破以日本为首的国家对我国离子膜产品的技术封锁,实现具有我国自主知识产权的离子膜技术的产业化。制备条件温和、制备工艺简单、快捷,而且整个过程没有传统方法中常用的季铵化或磺化步骤,有效地简化工艺和降低环境污染,可用于扩散渗析、普通电渗析以及双极膜电渗析过程对高性能离子交换膜材料的需求。该系列离子交换膜在特种废水处理、有机酸生产、氨基酸分离纯化、重金属废水处理等诸多领域得到了广泛的使用,均取得了较为满意的使用效果。     

电渗析和离子交换耦合过程对苏氨酸发酵液脱盐处理

苏氨酸作为一种高附加值的精细化工产品,具有广泛的应用前景.本文采用电渗析(ED)和离子交换(IX)两种方法处理苏氨酸发酵液,并研究了将这两种方法进行耦合的电去离子技术(EDI)的脱盐效果.ED过程中,改变料液浓度和回收次数,结果表明,在30V工作电压下操作最为有利;料液稀释倍数越大,越快达到脱盐终点,苏氨酸回收率越高,过程能耗也越低;能耗和回收率的数据表明,进行一次回收ED后不适合再继续进行ED回收苏氨酸.对于IX过程,使用717型树脂,对硫酸盐的脱除率和吸附容量分别能达到44.02%和33.88mg/g;树脂用量越多,吸附率越高(31.92%~74.73%),但吸附容量逐渐降低(38.43~14.99mg/g);发酵液初始浓度增大,溶液中吸附质离子增多,树脂的吸附容量增加.对于EDI过程,达到脱盐终点的速度比ED过程更快,脱盐效率也更高.综合效果表明,混合添加5mL Na型和5mL Cl型树脂,采用EDI过程处理发酵液,在能耗(0.269kW·h/L)和脱盐速率方面都更有优势.     

（HF）高性能电渗析器用离子交换膜介绍

研究了自制的高性能阴阳离子交换膜在电渗析器上的性能。采用了比较苛刻的介质对离子交换膜的性能进行了考验。结果表明，在连续运转１５个月后，离子交换膜本身的电学性能没有明显变化，并且电渗析器的操作性能与初装时相近。这充分说明我们自制的阴阳离子交换膜具有较好的电学性能和比较理想的使用寿命，在电渗析器上的应用是成功的。     

金属膜在1,3-丙二醇发酵液预处理中的应用

考察了1,3-丙二醇发酵液金属膜过滤在不同浓缩比下的拟稳定通量、黏度及湿固含量变化,在此基础上初步探讨了膜的污染机理,提出了有效的膜清洗方法.结果表明:50 nm的膜适用于1,3-丙二醇发酵液的膜过滤,按料液体积35%,加入去离子水、浓缩倍率在9左右时回收率达到95%.膜污染的主要来源是蛋白,有效的化学清洗方法是:用质量分数为1%NaOH和0.05%EDTA混合溶液清洗膜30 min后,再以0.5%HNO3溶液清洗5 min,膜通量可迅速恢复.     

原油对离子交换膜的污染及机理研究

通过含油污水对三槽电渗析的离子交换膜污染评价实验,发现原油对阴膜和阳膜污染的方向和程度都不同,阴膜为淡化室一侧且污染程度较严重,而阳膜为浓缩室一侧且污染程度较重;最后通过理论分析阐明了原油对阴膜和阳膜污染的机理.     

电去离子过程水解离机理的研究(Ⅲ)阴膜和阴树脂的降解对水解离的影响

通过对离子交换树脂与膜的污染与降解的分析,认为在常规的ED（电渗析）过程中,导致阴膜电阻增大并进一步诱发阴膜异常极化和水解离的主要因素是膜污染;而在电去离子（EDI）过程中,导致膜对电阻增大的主要因素则是阴膜和阴树脂的持续降解．根据弱碱性的叔胺化合物对阴离子交换膜的催化效应理论,对EDI过程浓缩水pH的演变认为阴膜和阴树脂一定范围内的逐渐降解过程,对应着其催化水解离反应逐渐加强的过程．此外,实验测定了EDI过程中阴阳离子交换膜的面电阻的变化情况,确证了阴膜降解反应的存在。     

均相离子交换膜在我国若干工业领域的应用

介绍了我国己批量生产的均相阴、阳离子交换膜的制造方法及其电化学性能指标，并且详细阐述了这些膜在填充床电渗析制造高纯水、造纸黑液的处理、甘氨酸的分离和纯化对及d-酒石酸钠生产d-酒石酸等若干工业领域的应用所取得的成果．我国已能生产用于上述领域的成套均相阴、阳膜组装的电渗析设备．     

以络合金属作催化剂的双极膜制备及电学性能

基于国内尚没有市售的良好双极膜,本研究以氯甲基化聚砜和磺化聚苯醚作为双极膜的阴阳膜层,在双极膜中间界面层固定络合金属作为催化剂,分别利用SnSO4、CrCl3、NiSO4作为催化剂制得3种双极膜,并与不添加任何催化剂制得的双极膜进行了比较.实验表明,络合金属对双极膜水解离有很好的催化作用,当中间界面层含有络合金属催化剂时,双极膜的水解离电势大大降低,并得到3种络合金属的催化活性为:Cr3+>Ni2+>Sn2+;过多催化剂用量会使双极膜的膜电阻增加;络合金属催化剂对双极膜的选择透过度影响不大,可以忽略;双极膜中间界面层中的络合金属催化剂与阴阳膜面的附着力不强,在酸碱环境中有些出现脱落或溶解.     

Electrically facilitated molecular transport. Analysis of the relative contributions of diffusion, migration, and electroosmosis to solute transport in an ion-exchange membrane

Electrically facilitated molecular transport in an ion-exchange membrane (Nafion, 1100 equiv wt) has been studied using a scanning electrochemical microscope. The transport rates of ferrocenylmethyltrimethylammonium (a cation), acetaminophen (a neutral molecule), and ascorbate (an anion) through approximately 120-micron-thick membranes were measured as a function of the iontophoretic current passed across the membrane (-1.0 to +1.0 A/cm2). Transport rates were analyzed by employing the Nernst-Planck equation, modified to account for electric field-driven convective transport. Excellent agreement between experimental and theoretical values of the molecular flux was obtained using a single fitting parameter for each molecule (electroosmotic drag coefficient). The electroosmotic velocity of the neutral molecule, acetaminophen, was shown to be a factor of approximately 500 larger than that of the cation ferrocenylmethyltrimethylammonium, a consequence of the electrostatic interaction of the cation with the negatively charged pore walls of the ion-exchange membrane. Electroosmotic transport of ascorbate occurred at a negligible rate due to repulsion of the anion by the cation-selective membrane. These results suggest that electroosmotic velocities of solute molecules are determined by specific chemical interactions of the permeant and membrane and may be very different from the average solution velocity. The efficiency of electroosmotic transport was also shown to be a function of the membrane thickness, in addition to membrane/solute interactions.     

Concentration and purification of chromate from electroplating wastewater by two-stage electrodialysis processes

A designed two-stage electrodialysis system is proposed to concentrate and purify chromate from a low pH electroplating wastewater using monovalent selective electrodialysis membranes. With low pH of the raw water (pH 2.2) in the first stage, chromate was presented as HCrO(4)(-) and monovalent ions (HCrO(4)(-), NH(2)SO(3)(-), Na(+) and Cl(-)) were able to pass through the membrane thus chromate was concentrated up to 191%. Higher current density, flowrate and more membrane area all increased the chromium recovery. When pH was adjusted to 8.5 before entering the second stage, the chromate species was presented as divalent CrO(4)(2-) and retained in the concentrated stream, and the rest monovalent ions (NH(2)SO(3)(-), Na(+) and Cl(-)) were separated by passing through the membrane. For example, 45% of the chlorides were separated in this study. The separation efficiencies in the second stage were also increased when the current density, flowrate and membrane area were increased. Electron Spectroscopy for Chemical Analysis was used to examine the surface chromate species for stage 1, and anion exchange membrane showed more chromate fouling comparing to cation exchange membrane due to more adsorption and concentration polarization effects for the anion exchange membrane.     

聚吡咯复合膜材料制备、表征及阳离子交换性能研究

以活性炭纤维(ACF)为基底电极,采用电化学恒电位聚合法制备了掺杂十二烷基苯磺酸阴离子(DBS-)的聚吡咯(PPy)复合膜(ACF/PPy/DBS),分别考察了聚合时间为0.5h和1h的两种复合膜(APD0.5和APD1)对Ca2 的离子交换性能和电流效率,并使用扫描电镜表征和分析了复合膜的形貌。结果表明,复合膜的膜厚随聚合时间的延长而增加,膜厚与Ca2 的交换量成正比,但对离子交换的电流效率没有明显影响。在Ca2 的掺杂过程中,复合膜内Ca2 离子的掺杂量和电流效率随阴极极化电位的负移而增大;在Ca2 的解析过程中,复合膜内Ca2 离子解析的电流效率随阳极极化电位的正移而降低,但解析量的变化不大。     

Synergistic pseudo-hydroxide extraction: synergism and anion selectivity in sodium extraction using a crown ether and a series of weak lipophilic acids

The nature of the weak lipophilic acid used in synergistic combination with a model crown ether cation host was shown to have a strong effect on the strength and selectivity of sodium hydroxide separation from alkaline aqueous salt solutions. Sodium ion-pair extraction employing only cis-syn-cis-dicyclohexano-18-crown-6 (1) in nitrobenzene (NB) was correlated with the standard Gibbs energy (deltaG(p)o) of anion partitioning into NB and was notably weak and nonselective for the hydroxide ion, in accord with Hofmeister bias. The Hofmeister order can be selectively overcome for NaOH by utilization of acid-base chemistry coupled with complexation of sodium ion in the NB phase. Upon addition of a lipophilic organic acid into the solution of 1 in NB, sodium extraction was selectively enhanced due to the initiation of an exchange reaction between the aqueous sodium ion and the ionizable proton of the organic acid. A series of weak lipophilic hydroxy acids (HA) including fluorinated alcohols and phenols was tested. The resulting synergistic pseudo-hydroxide extraction correlates with the pKa of the employed HA; the most acidic cation exchangers provide the greatest synergism. The synergistic factor obtained using a fluorinated benzyl alcohol 7 was as high as 256. Ion-pair extraction of neutral sodium salts was not changed or only mildly enhanced by addition of HA into the NB solution of 1. This enhancement was explained by hydrogen bonding of HA with the anion as related to the hardness of the anion and the acidity of HA. In comparison with the synergism observed for NaOH, this enhancement was weak and unable to overcome the Hofmeister effect. Examination of extraction selectivity revealed that the combination of 1 and 7 preferentially extracted NaOH over all other sodium salts, including the normally preferred nitrate and perchlorate salts. Quantitative recovery of NaOH from the NB phase was demonstrated via hydrolysis of the organic acid upon a single contact of the loaded solvent with water.     

Nonmolecular solvents in separation methods: dual nature of room temperature ionic liquids

Room temperature ionic liquids (RTIL) are molten salts starting to be used as nonmolecular solvents in separation methods mainly for their extremely low vapor pressure and thermal stability. RTILs are formed by an anion associated to a cation. This intrinsic structure gives them a dual nature. When used as additives in RPLC mobile phases to enhance basic compound separation, RTILs lose their particular physicochemical properties to become just salts. However, a given RTIL is not equivalent to another one made with the same cation. It is shown that both the anion and the cation contribute to solute retention and peak efficiency extending beyond simple "salting-out" or ion-pairing effects. Nine different alkyl-methyl-imidazolium ionic liquids with different alkyl chain length and chloride or BF(4-) or PF(6-) anions were used as additives (50 mM max. conc.) in the liquid chromatography separation of some cationic basic solutes on a Kromasil C18 column. It is shown with sodium salts and an acetonitrile-water 30/70 v/v mobile phase that anions can adsorb on the stationary phase surface according to their lyotropic character. They can also form ion pairs with the cationic basic solutes. Alkyl-imidazolium cations also adsorb on the C18 bonded stationary phase due to hydrophobic character depending on their alkyl chain length. Anion adsorption dramatically increases the cationic solute retention factors when cation adsorption decreases them. The cation adsorption is mainly responsible for peak shape and efficiency enhancements. RTILs are additives that enhance the basic cationic solute peak shape changing peak position. A wise choice of the appropriate combination of anion lyotropy with imidazolium cation hydrophobicity allows playing with solute selectivity and analysis duration.     

基于交流阻抗法的离子交换膜电阻研究

利用交流阻抗谱测定技术,建立一种离子交换膜导电性能评价方法;使用两极室槽电解池,分别测得电解质溶液,以及膜和电解质溶液之和的电阻值,相减后得到离子交换膜在该电解液中的电阻值.通过并联电阻形成完整的半圆弧形交流阻抗谱,能够有效减小测量误差.利用硫酸水溶液体系、氯化钠水溶液体系,以及全钒液流电池的钒电解液体系验证基于交流阻抗谱的膜电阻测定技术准确性、实用性.在此基础上揭示阳离子交换膜、阴离子交换膜对离子的不同吸附特性,以及膜面电阻对电解质溶液浓度依存特性.研究结果对于发展离子交换膜快速表征技术,以及开发新能源领域的离子交换膜具有重要价值.     

电子离子净水技术

介绍了电去离子（EDI）净水技术，讨论了笔者建立的反应叠加实用分析方法，并用它分析说明低含盐量时和高含盐量时应用EDI净水的工况。