发酵液中乳酸的电渗析法分离

采用电渗法分离发酵液中低浓度乳酸,考察了电渗析器的操作条件对极限电流密度和乳酸电年速率的影响,并分别用修正的Ｗｉｌｓｏｎ公式和乳酸电渗析速率方程描述了它们之间的关系。     

乳酸发酵液电渗析过程中氨基酸的迁移现象

使用三室双极膜电渗析法处理乳酸发酵液时,杂质氨基酸的迁移会影响回收乳酸的纯度. 通过对乳酸发酵液电渗析过程中氨基酸迁移现象的研究,发现各种不同氨基酸的迁移速率主要受其初始浓度、pI值与料室pH值的差值、阴离子交换膜对其选择性及其自身电迁移率的影响. 根据此规律,建立了离子迁移速率计算模型,通过与实际过程比较,表明其可有效预测杂质氨基酸的迁移情况,估算特定体系达到预定收率时的纯度. 实验验证结果表明,氨基酸的迁移率为32.5%,与对照实验(82.6%)相比,降低率为60.7%. 通过调节氢渗漏控制料室pH值、提高阴膜对乳酸的专一选择性等可控制氨基酸向酸室迁移,以获取更高的乳酸纯度.     

pH值对电渗析法回收厨房垃圾发酵液中乳酸的影响

随着人们环保意识的加强,乳酸作为生物可降解塑料的原料日益受到重视．目前,国内外一些专家都在积极开发廉价乳酸的分离新工艺,如萃取、电渗析、反渗透．电渗析法作为一种新的膜分离技术过去主要运用在苦咸水及海水的淡化上,现在欧美、日本等一些发达国家已运用电渗析法来分离、浓缩回收化工产品．     

双极膜电渗析法连续制备聚合硫酸铁

研究了双极膜电渗析法连续制备聚合硫酸铁（PFS）的工艺。主要考察了电流密度、原料补充液中硫酸亚铁和硫酸的摩尔比以及原料补充液流速对产品PFS各性能指标（盐基度、全铁含量、pH、密度等）和过程能耗的影响。研究结果表明：电流密度从10mA/cm²增加到20mA/cm²时,盐基度从8.59%显著增加到11.32%,去浊率从84.31%逐渐增加到95.34%,但当电流密度大于20mA/cm² 时,盐基度和去浊率稍有下降,过程能耗最高可达4.26kW·h/kg H₂SO₄,酸液罐酸浓度最高可达0.45mol/L;原料补充液中硫酸亚铁和硫酸的摩尔比从2.01增加到4.08时,盐基度从8.69%增加到11.38%,去浊率从94.96%逐渐增加到95.88%,能耗在3.05~3.15kW·h/kg H₂SO₄ 范围内变化,酸液罐酸浓度约为0.38mol/L;原料补充液流速从1mL/min增加到3mL/min时,盐基度从11.52%下降到6.75%,去浊率从95.92%逐渐降低到75.61%,同时,能耗从3.09kW·h/kg H₂SO₄下降到2.77kW·h/kg H₂SO₄。     

电渗析法制备水溶性离子液体

以1-乙基-3-甲基咪唑四氟硼酸盐（［EMIm］BF₄）的制备为例,对四隔室电渗析法制备水溶性离子液体进行了研究。分别考察了操作电压、进料浓度和离子交换膜种类对平均电流效率、能耗和收率3个电渗析过程性能参数的影响。实验结果表明,相比于传统的化学合成法制备离子液体,采用四隔室电渗析法制备水溶性离子液体具有反应条件温和（室温下反应）、反应时间短、反应无须传统有机溶剂（水作反应溶剂）和产物纯度高（最高可达98％）的优点。     

电渗析法分离医疗垃圾焚烧飞灰浸出液中重金属

采用电渗析法分离医疗垃圾焚烧飞灰浸出液中重金属,考察了电流密度、液固比、处理时间等参数对重金属移除的影响,并分析了电渗析处理对飞灰特性、重金属形态及其浸出毒性的影响. 结果表明,电流密度0.8 mA/cm2、液固比10(w)和处理时间14 d条件下飞灰浸出液中重金属分离效果最好,11.1% Pb, 42.3% Zn, 56.7% Cd, 38.7% Cu, 7.5% Cr被移除,飞灰中大量NaCl被移除,氯含量从20.43%降低到0.78%,热灼减率从11.1%升高到34.3%,可溶态和碳酸盐态重金属含量降低,飞灰基质减少及不可溶态重金属存在导致残灰中重金属含量增加,Pb和Cd浸出浓度仍超过生活垃圾填埋场的阈值.     

双极膜电渗析法由硫酸铵制备硫酸的工艺研究

利用两室双极膜电渗析法从硫酸铵溶液中制备硫酸。探讨了电渗析过程中的电流效率、能耗、产酸量等指标。实验结果表明,产酸量随时间的延长而增加,在恒定电流密度（0.09A.cm-2）的条件下,硫酸的电流效率达到90%,能耗为2.5～2.6kW.h.kg-1。     

发酵液中乳酸的分离提取研究进展

乳酸是合成聚乳酸的原料,生物法制备乳酸是目前工业上生产乳酸的主要方法。但乳酸发酵液成分复杂,后续的分离提纯过程成了制约乳酸生产的技术瓶颈和难点,也决定着乳酸的品质与收率。本文对乳酸发酵液的主要的分离提取工艺进行了介绍,包括结晶分离技术、酯化水解法、萃取法、分子蒸馏法、膜分离法、吸附法及与发酵耦合的原位分离技术。并提出单一的分离技术很难有效提取乳酸,需将多种技术集成、改良提纯工艺路线。其中,将各种新型高效的集成技术与发酵过程的有机结合,实现连续或半连续的发酵过程,可提高乳酸产率和产品质量,有望形成高效率、高品质、低污染、低能耗、可工业化的乳酸提纯工艺路线。     

从发酵液中分离乳酸的新工艺

介绍了采用膜分离与离子交换相结合分离乳酸的新工艺。与传统的乳酸钙结晶法相比，新工艺具有提高产品收率、降低生产成本、缩短生产周期等优点。     

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。     

Lactic acid recovery from fermentation broth using one‐stage electrodialysis

One‐stage electrodialysis (ED) for lactic acid recovery with two‐ and three‐compartment water‐splitting ED (WSED) was investigated using various ion‐exchange membranes in order to overcome the inefficiency of two‐stage ED, which consists of desalting ED for recovery and partial purification and subsequent WSED for acidification. The two‐compartment WSED had a low current efficiency and high energy consumption in spite of a simple stack configuration. A three‐compartment WSED successfully converted sodium lactate in the fermentation broth into lactic acid and sodium hydroxide with average yields of 96% and 93%, respectively. In relation to lactic acid purification, of the membranes tested in this study, the highest glucose rejection, 98.3%, was achieved using a PC 100D membrane. The CMS membrane rejected magnesium and calcium at levels as high as 81.7% and 78.5%, respectively. We concluded that the three‐compartment WSED with properly chosen membranes, enabled lactic acid to be recovered directly from the fermentation broth. © 2001 Society of Chemical Industry     

用电渗析法从谷氨酰胺模拟发酵液中脱除谷氨酸

为改进微生物发酵法生产谷氨酰胺的流程,提出用电渗析方法来分离谷氨酰胺和谷氨酸。在对混合氨基酸溶液中离子成分进行分析的基础上,预测了此方法的可行性,并通过电渗析方法对模拟发酵液进行实验来验证此预测结果。还考察了在混合物中含有硫酸铵时的情况。通过理论预测和实验验证,可以用电渗析法直接分离谷氨酰胺和谷氨酸,且原料中少量的硫酸铵有利于分离过程的进行。     

Recovery of alpha-ketoglutaric acid from model fermentation broth using electrodialysis with bipolar membrane

ABSTRACT

A bipolar (BP) membrane electrodialysis (EDBM) was used to recover the alpha-ketoglutaric acid (AKG) from the model broth. A two-chamber EDBM membrane stack consisting of an anion exchange membrane and a BP membrane was used. The effect of the initial composition, applied current density, and pH of diluate on the efficiency of EDBM processes was investigated. The obtained results showed that the used membrane stack configuration allows complete separation of AKG from glucose and ethanol and simultaneous conversion of AKG salts to the acidic form. The scale-up of the EDBM process for model fermentation broth was also carried out.     

Membrane fouling caused by amino acid and calcium during bipolar membrane electrodialysis

BACKGROUND: Bipolar membrane electrodialysis (BMED) has been widely applied in the recovery/production of organic acids and in the treatment of wastewater containing ammonium sulfate, sodium nitrate, sodium acetate and ammonium nitrate. However, membrane fouling is still one of the major problems in the electrodialysis process. Since calcium and amino acid are present naturally in fermentation wastewater, this study was carried out to determine the effects of calcium and amino acid on membrane fouling when simulated fermentation wastewater containing ammonium sulfate was treated by BMED. RESULTS: Calcium formed a scale on the cation exchange membrane (CEM) surface in contact with the base cell, but this had no significant adverse effect on the BMED performance. Amino acid, however, caused CEM fouling of the inner membrane, which hampered the BMED process. The coexistence of calcium and amino acid aggravated the membrane fouling, as observed morphologically on the CEM surface on the base cell side. Elemental mapping analysis showed that the membrane foulant was composed of calcium hydroxide and amino acid. CONCLUSION: The CEM fouling caused by calcium and that due to amino acid, which were distributed differently on the membrane, had different effects on the BMED performance. The coexistence of amino acid and calcium deteriorated the CEM fouling during BMED. Copyright © 2008 Society of Chemical Industry     

Asymmetric bipolar membrane electrodialysis for acid and base production

Bipolar membrane electrodialysis (BMED) is a promising technique for upgrading traditional manufacturing procedures and achieving a circular economy. However, the industrial applications of BMED technology have been restricted by the large consumption of expensive bipolar membranes and the unmatching behavior between water splitting and ion migration. Herein, we proposed a novel asymmetric bipolar membrane electrodialysis (ABMED) to regulate the water splitting in the bipolar membrane and orientational ion migration in the electrodialysis (ED). It was found that the ABMED exhibited comparable performances to BMED for acid/base production when the area of the bipolar membrane was reduced to 50% of the monopolar membrane. The total process cost of ABMED was 0.78 $/kg NaOH, which is 21% lower than the BMED process. The asymmetric membrane design was capable to boost the water splitting in the bipolar membrane and to eliminate the concentration polarization in the ED process.     

Efficient recovery of ionic liquid by electrodialysis in the acid hydrolysis process

Electrodialysis (ED) has been recently known as a highly effective technique to remove and recover ionic liquids from aqueous solution. When a conventional electrolyte solution for the ED process containing Na₂SO₄ was used, a recovery ratio of an acidic IL, 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO₄]), was 90%. On the other hand, the value clearly increased to 96% when we employed [Bmim][HSO₄] as the electrolyte solution. In an acid hydrolysis of bagasse using the IL under microwave irradiation, the recovery ratio maintains 96%, irrespective of reaction time. This demonstrates the applicability of the proposed ED system in biomass processing.     

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.     

双极膜电渗析法麦草畏生产废水的资源化利用研究

采用双极膜电渗析（bipolar membrane electrodialysis,BMED）将麦草畏生产废水中的NaCl转化为HCl和NaOH回用于农药生产,实现农药废水的资源化利用。首先进行了BMED法处理单组分NaCl溶液体系的110 min间歇运行实验来探索最优操作条件,结果表明,当NaCl初始浓度为160 g/L,电流密度为70 mA/cm²,初始酸碱室浓度为0.075 mol/L时,产物HCl、NaOH的浓度能分别达到1.98 mol/L和 2.06 mol/L,且此时的电流效率较高,达到42.74%。然后考虑实际废水的COD指标主要是甲醇造成的,所以用含不同浓度甲醇的NaCl溶液模拟实际农药废水,实验结束后在酸、碱隔室中检测到少量的甲醇,表明其在BMED运行过程中存在一定程度的渗透,但未对膜堆性能造成明显影响。最后用BMED处理经过预处理后含有机物的麦草畏生产废水,发现在操作时间内膜堆性能与处理高浓度单组分NaCl溶液情况类似,证实BMED法处理麦草畏生产废水并实现资源化利用的可行性。