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发酵料液电渗析过程膜污染机制与防治
其他题名Mechanism and Prevention of Membrane Fouling during Electrodialysis of Fermentation Feed
任洪艳
学位类型博士
导师丛威
2009-05-26
学位授予单位中国科学院过程工程研究所
学位授予地点过程工程研究所
学位专业生物化工
关键词电渗析 发酵料液 膜污染 机制 防治
摘要发酵工业中产品提取后残液含有丰富的可利用成分和其它水污染物质,实现废液资源化利用是实现清洁生产的关键。电渗析具有过程简单、效率高、废物排放少等特点,可降低物质和能源消耗、减少废物排放、消除环境污染,为某些物质资源的再生和回收、某些酸和碱的分离和制备,实现废液的资源化和清洁生产提供一种新途径,然而膜的污染和劣化却始终是制约电渗析技术工业应用的瓶颈。 本文针对两种发酵料液味精等电母液和赖氨酸离交废液的电渗析过程研究了离子交换膜的污染,观察了污染膜面的形貌,对污染物进行了成分分析,从而确定了污染物质及污染机制,并通过操作条件、预处理程度和膜的清洗等比较和评价了膜污染的防治。主要实验结果如下: (1)实验证实了以电渗析法处理发酵料液的工艺中膜污染严重:随批次的增加电渗析的效率逐渐降低,表现为能耗随批次增加逐渐增大,硫酸根转化率的逐渐减小。电渗析处理赖氨酸离交废液时膜污染程度较处理味精等电母液更为严重。 (2)通过扫描电镜(SEM)、X-射线能谱、凝胶色谱、红外光谱(FTIR)、RT-HPLC和XRD观察和分析膜面的主要污染物,结果为:双极膜电渗析处理味精等电母液后,料室侧膜污染物为易吸附堆积于膜面的有机物,碱室侧膜面污染物来源于料液中的带正电荷的氨基酸和二价金属离子;电渗析和双极膜电渗析处理赖氨酸离交废液过程中料室侧阴膜面污染物主要含有N、S、Fe、Mg、Ca和Na元素,且O元素的含量增大,阳膜面污染物主要含有Mg、Ca和Na元素,且碱室侧膜面的大量污染物含有Fe、Mg、Ca、O和C元素。 (3)以配制的模拟料液进行的实验结果表明,料液中的钙是引起碱室侧阳膜面出现固形污染物的主要因素;而料液中的氨基酸则会导致性能参数的恶化;两者共同存在会加重膜污染,且随浓度的增大污染程度加重。初步确定了膜污染的主要原因为:料液中的蛋白、胶体和聚合物等带不同的电荷,在电场力作用下发生迁移,会吸附、堆积于膜面。当浓度较高时,易发生聚集沉淀。碱室侧的污染则是由于料室母液中的金属离子在电场作用下跨过阳膜进入碱室,与双极膜水解离生成的OH-形成氢氧化物沉积。料液中含有的氨基酸在BMED过程中会跨阳膜进入碱室,氨基酸的存在形式会发生变化,导致溶解性和迁移速率减小,与膜产生较大的吸附力进而形成沉积。 (4)优化了电渗析等电母液的操作条件结果表明,影响最显著的是操作电流,较显著的是流速和温度,适宜的操作条件为:电流4.0 A,流速10 cm s-1,温度35 ℃,酸室初始浓度0.05 mol L-1。 (5)考察了多种预处理方式。结果表明,强化料液净化预处理可有效延缓膜污染,从而提高电渗析的效率。陶瓷膜微滤除菌体、超滤除蛋白和螯合树脂处理去高价离子为料液预处理的适宜方法。 (6)考察了多种清洗方式。结果表明,合适的清洗方法与操作周期可降低膜污染程度,从而提高电渗析的生产效率。料室和碱室较适宜的循环清洗液分别为0.5% NaOH和1%H2SO4。
其他摘要For cleaner production in traditional fermentation industry, it is essential to realize the utilization or circulation of nutrients and some pollutants in fermentation broth. Electrodialysis has emerged as a potential alternative for realizing cleaner production with the spentwash as a resource, by recovering some chemicals, reducing feedstock and energy consumption, and elimating environmental pollution. However, membrane fouling and deterioration is still one of the major obstacles in the electrodialysis process. In this thesis, ion-exchange membrane fouling was accumulated and observed during electrodialysis of two fermentation solutions, monosodium glutamate isoelectric supernatant and lysine ion-exchange wastewater. Based on the morphological and compositional analysis of membrane foulants, the fouling mechanism was investigated. Through operation condition optimization, pretreatment reinforcement and membrane cleaning up, some methods were developed to prevent membrane fouling. Some results were as follows: (1) Membranes were fouled seriously in the course of electrodialysis of pretreated fermentation solutions. And electrodialysis performances were deteriorated with batch runs, which manifested in increased energy consumption and declined conversion ratio. The membrane fouling extent for electrodialysis of lysine ion-exchange wastewater seems much severer than that of the monosodium glutamate isoelectric supernatant. (2) With scanning electron microscopy (SEM) morphological observation of the fouled membrane, the foulant was characterized by X-rays energy-dispersive analysis, gel-chromatogram, FTIR, RT-HPLC and XRD. After bipolar membrane electrodialysis (BMED) of isoelectric supernatant, the foulant on membrane surface beside salt cell was organic substance which adsorbed and accumulated amiably in the membrane, while that beside base cell was resulted from amino acids with positive charges and bivalent metal ions in feed. The membrane foulants after electrodialysis and bipolar membrane electrodialysis of lysine ion-exchange wastewater were as follows: foulants on anionic and cationic membranes surface beside salt cell comprised of N, S, Fe, Mg, Ca, Na and O elements, and Mg, Ca and Na elements, respectively. However, the foulants on membrane surface to base cell consisted of Fe, Mg, Ca, O and C elements. (3) The result of BMED of simulated fermentation wastewater was as follows: Calcium formed a scale on the cation exchange membrane (CEM) surface in contact with the base cell, while amino acid hampered the BMED process. And the coexistence of calcium and amino acid aggravated the membrane fouling. Based on the study above, the main reason of membrane fouling was analysed as follows. Some proteins, colloids and polymers carrying electric charges in fermentation broth would transfer under the electric field force and finally adsorb / accumulate on the membrane surface. As to the cause of base cell scaling, it was that, when some metal ions in the salt cell migrated through CEM into the base cell, they coupled with hydroxyl ions generated by the bipolar membrane and finally precipitated in the form of calcium hydroxide. On the other hand, during BMED, some amino acids with positive charges in the salt solution migrated through the CEM into the base cell. And they probably dehydrated and condensed into larger molecules such as peptides, which tended to be adsorbed on the membrane because of their poor solubility and mobility under the base condition. This was responsible for the organic foulants forming in BMED. (4) The operation condition of electrodialysis monosodium glutamate isoelectric supernatant was optimized. It was found that the most significant factor was operation current, and the secondary to it was flow velocity and temperature. Some optimal conditions was 4.0 A of the current, 10 cm s-1 of the flow velocity, 35 ℃ of temperature and 0.05 mol L-1 of the initial acid cell concentration. (5) Some pretreatment methods were compared. The result showed that membrane fouling course could be retarded effectively by reinforcing solution pretreatment, thus improving the electrodialysis performance. The feasible pretreatment methods included such as ceramic membrane microfiltration removing thalli, ultrafiltration withdrawing protein and chelated resin eliminating multivalent metal ion. (6) The membrane fouling could be reduced to some degree and the electrodialysis efficiency could be improved through selecting reasonable cleaning method and operation period. The suitable cleaning reagents for salt and base cell were, respectively, 0.5% NaOH and 1% H2SO4.
页数163
语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/1113
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任洪艳. 发酵料液电渗析过程膜污染机制与防治[D]. 过程工程研究所. 中国科学院过程工程研究所,2009.
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