液膜法迁移及分离镍(Ⅱ)的研究

本文采用内耦合大块液膜分离技术，考察了搅拌速度、料液相pH值、体系温度、载体浓度对镍(Ⅱ)迁移率的影响，研究了以烷基膦酸为载体的液膜中镍(Ⅱ)的迁移规律。结果表明，镍(Ⅱ)的迁移率随温度和载体浓度的升高而逐渐增大，当迁移条件为搅拌速度300～350r／min、料液相pH值5．3～5．8、载体浓度5．5％～7．5％、温度293～310K时，镍(Ⅱ)即可快速并完全迁移。     

烷基膦酸为载体的液膜中迁移铜(Ⅱ)的研究

本文使用烷基膦酸（PC－88A）－CHCl3内耦合大块液膜体系研究了Cu(Ⅱ）的迁移行为。探讨了料液相pH值、温度、载体浓度、金属离子浓度对Cu(Ⅱ）迁移速率的影响。结果表明，增加载体浓度或升高浓度、迁移速率明显升高，在pH值为3.5-5.0温度为288K－303K，载体浓度为5.00-7.00%时，Cu(Ⅱ）的迁移率可达99％以上。     

莲心碱与叶绿素膜分离的初步实验研究

研究了用膜分离技术进行莲心碱的提取。将待分离的料液进行了必要的预处理,重点考察了料液pH值和稀释浓度对分离效果的影响。比较了4种不同材质膜过滤料液时的稳定渗透通量、莲心碱回收率和叶绿素截留率情况,并利用膜阻力分析法得出污染膜的各阻力构成。实验结果表明,当pH值在3.0左右、叶绿素浓度在1.68～2.52 g/L时,莲心碱的分离效果最佳;由于聚醚砜膜有高通量、高分离效果,因此选择聚醚砜膜分离料液;阻力构成的分析结果表明,沉积层阻力Rc(38.6%)、膜阻力增加△Rm(26.9%)及浓差极化阻力Rp(22.8%)都是过滤阻力的主要组成部分。     

钙盐和氨基酸对味精等电母液模拟料双极膜电渗析过程膜污染的影响

采用恒压分批操作方式考察了味精等电母液模拟料液中钙盐和氨基酸对双极膜电渗析过程膜污染的影响.结果表明,在处理含氨基酸和Ca2+的盐溶液时,碱室溶液中检测到各氨基酸含量为Glu＞Ala＞Gly＞Thr＞Lys,它们与料液中NH4+同步迁移至碱室,迁移量与料液中氨基酸浓度成正比;料液中Ca2+是引起碱室侧阳膜面出现固形污染...     

PC-88A-煤油-HCl分散支撑液膜体系中Zn(Ⅱ)的传输与分离研究

以聚偏氟乙烯膜(PVDF)为支撑体,煤油为膜溶剂,2-乙基己基膦酸-单-2-乙基己基酯(PC-88A)为流动载体,研究了分散支撑液膜体系中金属Zn(Ⅱ)的传输行为;考察了料液pH、膜溶液与解析剂体积比和解析相中HCl浓度对Zn(Ⅱ)传输的影响.结果表明,以HCl为解析剂,料液pH为4.0、膜溶液与解析液体积比为160:40、解析相中HCl浓度为4.0 mol·L-1时,该分散支撑液膜体系对金属Zn(Ⅱ)具有良好的传输作用,传输190 min,传输率可达90%,在相同的条件下传统的支撑液膜只有72.8%.在Zn(Ⅱ)的最佳传输条件下,对Zn(Ⅱ)/Cu(Ⅱ)、Zn(Ⅱ)/Co(Ⅱ)进行了分离试验,分离效果很好,该体系能够实现金属离子的传输和分离.     

交联壳聚糖渗透蒸发膜的制备及其在偏二甲肼/水体系分离中的应用

采用壳聚糖为原料,聚酯无纺布为支撑层,用戊二醛交联制备了高选择性、高通量的交联壳聚糖渗透蒸发复合膜.考察了料液浓度、料液温度、膜厚等对偏二甲肼/水体系分离性能的影响.结果表明:在料液温度为10℃,膜厚度为25 μm,进料液中偏二甲肼的质量分数为50％时,改性复合膜的分离因子最高达到5.25,渗透通量可达167 g/(m...     

三正辛胺—煤油支撑液膜萃取Cd（Ⅱ）的研究

本文研究了Ｃｄ（Ⅱ）在三正辛胺－煤油支撑液膜体系中的影响Ｃｄ（Ⅱ）迁移的各种因素,并测定了有关条件下Ｃｄ（Ⅱ）跨越膜的渗透系数Ｐ。结果表明,膜相载体三正辛胺浓度适度增加,Ｃｄ（Ⅱ）迁移的渗透系数Ｐ增加,三正辛胺增至０．８ｍｏｌ／Ｌ时,Ｐ值下降,搅拌转速,料液中Ｈ＾＋浓度和Ｃｄ（Ⅱ）浓度,温度的影响Ｃｄ（Ⅱ）的迁移,反萃剂醋酸铵比氢氧化钠好,煤油比四氧化碳更适宜作膜溶剂,三正辛胺－煤油支撑液膜体系能     

电脱水技术应用于发酵产品固液分离的基础及特性

以酵母为模拟体系研究电脱水技术在发酵产品固液分离过程中的应用可行性. 考察了不同操作条件，包括酵母悬浮液初始pH、初始电导率、酵母浓度及电流强度对脱水率的影响，测定了上述条件下酵母细胞表面电动电位(即z电位)的变化规律. 研究结果表明，酵母细胞的表面电性质与电荷密度决定着电脱水过程的速率及脱水率.     

反应与分离相耦合的钢铁酸洗液处理研究

采用反应与分离相耦合的途径,用19通道陶瓷膜元件构建了5L气升式膜反应器,并就其用于钢铁酸洗液的处理进行了研究.结果表明:在0.5～2.5 m~3/h曝气量范围内,稳定膜通量能维持在60L/(m~2·h)以上,且提高曝气量有利于提高循环液体流速.在稳定操作条件下,料液中氢氧化铁悬浮物浓度、温度(1～45℃)和膜两侧压差(0.025～0.1MPa)均与膜通量呈线性关系.当处理Fe~(2+)质量浓度为400ms/L的酸洗废液时,在溶氧度>70%、压差0.1 MPa、18～25℃、pH为6-9、HRT=2h条件下,出水浊度<2 NTU,pH符合国家排放标准.     

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.     

纳滤分离提取谷氨酰胺过程的研究

对发酵液中的谷氨酰胺提取进行了采用纳滤膜分离技术的尝试，并对谷氨酰胺和谷氨酸混合溶液的纳滤分离进行了理论分析。研究了不同pH条件下发酵液中谷氨酰胺和谷氨酸在纳滤过程中的透过特性，并考察了纳滤过程中氨基酸的透过特性随压力和浓度的变化。结果表明：当发酵液pH=7，谷氨酰胺浓度为1％时，纳滤膜分离谷氨酰胺的提取总收率可达到65％以上。     

透明质酸分离纯化研究进展

微生物发酵法是生产透明质酸的主要方法,分离纯化是发酵法制备高分子量、高纯度透明质酸的关键环节。本文探讨了透明质酸发酵液的特性和分离纯化过程中工艺条件对透明质酸分子量和结构的影响,对预处理、分离、纯化各阶段的工艺方法进行了系统比较和分析,指出了透明质酸分离纯化工艺中存在的问题,并提出了今后分离纯化研究的重点。     

发酵液的组成对纳滤分离谷氨酰胺的影响

研究了谷氨酰胺发酵液中盐离子对纳滤分离提取谷氨酰铵的作用，系统地考察了操作温度和发酵液组成对纳滤分离透过特性的影响，确定了纳滤分离时发酵液最佳稀释倍数和操作温度. 结果表明，二价阳离子通过改变膜面电荷密度对谷氨酸的透过特性产生很大影响，使其截留率降低了8%. 发酵液中较高浓度的(NH4)2SO4使谷氨酸和谷氨酰胺的截留率和透过通量明显降低，但较高浓度的NH4Cl影响较小，这体现了纳滤膜对不同离子排斥力的差异. 当发酵液稀释至谷氨酰胺浓度为1%，pH调至7时，发酵液中的其它盐离子和残糖因浓度较低而对纳滤分离影响不显著.     

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。     

Downstream Processing of Lactic Acid by Membrane-Based Solvent Extraction∗

Abstract

Lactic acid has extensive use in the food and chemical industry. About half the lactic acid used in the world is produced by fermentation of carbohydrates using lactic acid bacteria. The recovery of lactic acid from the fermentation broth is more difficult than the fermentation itself. In the present work a study of membrane-based solvent extraction as a separation unit for the continuous downstream processing of lactic acid from fermentation broth was carried out. The experiments were performed using simulated fermentation broths made of lactic acid in acetate buffer or distilled water as the feed solution. The effects of membrane material, organic carrier, and pH of the feed solution on membrane extraction efficiency were investigated. A separation degree of 35% was obtained by using a polyether-etherketone (PEEK-WC 14%) membrane with 5% trioctylamine as the organic carrier in n-heptane. The experimental results obtained with the simulated system encourage the use of membrane-based solvent extraction with a real fermentation broth.

     

生物基有机酸提取分离技术研究进展

有机酸如乳酸、琥珀酸、柠檬酸、衣康酸、苹果酸等在工业上有重要应用,随着食品、医药、化学合成等工业的发展,有机酸需求骤增,发酵生产有机酸逐渐成为生物工程领域中一个重要而成熟的分支,但存在产物浓度低、成分复杂、后处理量大等问题. 有机酸亲水性好、不同有机酸物理化学性质相近等特点导致产物分离提纯困难,成为制约生物法生产有机酸的瓶颈. 分离发酵液中有机酸的方法主要有沉淀法、萃取法、吸附法、离子交换法、膜分离法、电渗析法和酯化法等. 通过各种分离方法的对比,发现单一的分离方法很难有效分离有机酸. 集成不同分离方法,可简化分离工艺,分离效果更好. 此外,采用新型分离耦合技术,可实现有机酸的连续或半连续生产,是未来发酵行业的一个重要发展方向.     

Purification of lactic acid from fermentation broth by spherical anion exchange polymer

Lactic acid, as a versatile chemical, was purified from fermentation broth by solid phase extraction with a spherical porous poly(4‐vinylpyridine). Adsorption isotherm of lactic acid on poly(4‐vinylpyridine) was first investigated with model solutions. The factors which affect the performance of separation and purification were then investigated. The obtained results indicate that the sorbent had a high adsorption capability of lactic acid, of which the maximum adsorbed lactic acid was 180.0 mg g⁻¹. Under the optimal condition the lactic acid was purified from fermentation broth by solid phase extraction with the purity of 88% and recovery yield of 95%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

MATHEMATICAL MODEL OF L-LACTIC ACID FERMENTATION IN A RDC COUPLED WITH PRODUCT SEPARATION BY ION EXCHANGE

A Rotating Disk Contactor (RDC) was designed to perform the L-lactic acid fermentation with a filamentous fungus, Rhizopus oryzae, which was immobilized on the surface of rotating disks. The bioreactor was operated in repeated batch or continuous modes. The growth rate of the fungi was about 1 mm/day perpendicular to the disks' surface. A weak-base anionic resin, D354, was selected which was high in selectivity for lactic acid separation. Even at low concentration, the ion exchange capability was about 0.5 g Lac/g dry resin. A coupled process of L-lactic acid fermentation and ion-exchange separation was evaluated experimentally. The results indicated that the pH value of the fermentation broth could be maintained at pH 3.5 without any addition of alkali. The conversion ratio of glucose to L-lactic acid was about 0.7 g/g and the fermentation rate was able to reach as high as 62.5g glucose per hour per square meter of the disk surface area. A mathematical model was proposed to describe the simultaneous process of L-lactic acid fermentation and separation by ion exchange, in which the thickness increase of mycelia as well as the substrate and product inhibitions were included. The model simulation was in good agreement with the experimental data.     

Extraction of lactic acid into sunflower oil and its recovery into an aqueous solution

Demand for lactic acid is growing, especially, for its use in the production of biodegradable polymer (polylactate). The current method of production and separation of lactic acid is both expensive and unsustainable. This is partly due to the cost and lower efficiency of the current method for separating the lactic acid product from the fermentation media. Therefore, the development of alternative technology that will offer efficiency, economic and environmental benefits is of great importance. One of the promising technologies for recovery of lactic acid from fermentation broth is reactive liquid–liquid extraction. In this paper, processes based on reactive extraction of lactic acid into an organic phase and its recovery into an aqueous phase is examined. The percentages of extraction and recovery are determined by using a small pilot-scale microporous hollow-fibre membrane module (HFMM). Firstly, equilibrium experiments were conducted using organic solutions consisting of Aliquat 336 and trioctylamine (as carriers) and tributyl phosphate and sunflower oil (as solvents) The values of the distribution co-efficient (defined as a ratio of the concentration of lactic acid extracted over that remaining in the aqueous solution at equilibrium) were obtained as a function of feed pH (range 4.0–6.5), composition of the organic phase (ratio of carrier to solvent) and temperature (range 8–40°C). The best extraction was obtained with the organic phase of 15wt% tri-octylamine (TOA), 15% aliquat 336 dissolved in 35 wt% tri-butyl phosphate (TBP) and 35% sunflower oil. The percentage extraction from 0.1 M was approx. 70% after 4 h at pH 5.0 and at 35°C at a recirculating flow rate of 15–20 L/h. Lactic acid was reextracted from the organic phase by using 0.5 M sodium carbonate solution and approx. 90% recovery was obtained in 4 h. These results demonstrate that good extraction and recovery of lactic acid in the hollow-fibre membrane are possible. Also because of its potential for application in situ the process would allow to maintain lactic acid concentration at low levels during the fermentation and to improve productivity by suppressing the product inhibition effects.     

过滤法分离纯化透明质酸

针对透明质酸的分离纯化,提出了用过滤法分离纯化透明质酸的工艺. 首先以20 g/L的溶解浓度将透明质酸粗品溶于去离子水中,并加入硅藻土作为吸附剂,调节溶液pH至4.6~4.8;然后采用硅藻土过滤、滤板过滤、超滤,用乙醇结晶后可得葡萄糖醛酸含量高达44.2%的透明质酸. 该工艺已成功应用于工业生产,所得产品的葡萄糖醛酸含量达47.3%,蛋白质含量为0.01%,相对分子量可达110万,收率高达90.5%.