【作者】 罗铁红；

【导师】 陈碧娥；

【作者基本信息】 华侨大学 ， 生物化工， 2006， 硕士

【摘要】 乳酸是一种重要的有机酸，可用于制造可生物降解材料聚乳酸。传统的乳酸生产存在着工艺流程长、消耗原料多、环境污染等问题。为避免上述问题，本研究采用双极膜或离子交换膜电渗析法将发酵液中的乳酸盐转化为乳酸。该方法的主要优点在于收率高、能耗低，有望用于工业化生产。论文研究了双极膜和离子交换膜电渗析法从乳酸钠模拟液、离子交换膜电渗析从乳酸钙模拟液和发酵液制备乳酸的工艺条件，并对制备的乳酸进行了质量分析。 在双极膜电渗析中，乳酸钠转化为乳酸，并得到纯度比较高的氢氧化钠。在95％乳酸钠转化率条件下，电渗析的能耗在2.5-3.5kWh／kg左右，电流效率在60％左右，乳酸的回收率可以达到90％。研究中采用北京双极膜和JCM-I阳膜比较好。电流、乳酸钠和NaOH初始浓度对电渗析过程影响很大。在分批操作中，选择2.5A的电流，乳酸钠和NaOH仞始浓度分别为0.7mol／L和0.1mol／L时能达到最好的实验结果。 在离子交换膜电渗析从乳酸钠制备乳酸中，利用三室的电渗析器在外加硫酸的条件下将乳酸钠转化为乳酸，同时得到硫酸钠。乳酸回收率和电流效率都在90％以上，能耗在0.7kWh／kg左右。电渗析过程中采用高浓度的乳酸钠能降低过程的能耗；使用JCM／JAM-I膜得到高的乳酸回收率；脱色对电渗析过程影响不大。与双极膜电渗析法相比，离子交换膜电渗析法的主要优点是膜成本低、效率高、能耗低。 在电渗析法从乳酸钙制备乳酸中，利用三室的电渗析器在外加盐酸的条件下乳酸钙转化为乳酸，同时得到氯化钙。钙离子脱除率和电流效率都在90％以上，能耗为0.6kWh／kg左右。实验得出的优化条件为：JCM／JAM-I膜，电流设定在3A。而利用乳酸钙发酵液实验时，钙离子脱除率和电流效率与模拟液相差很大，能耗在1kWh／kg以上。乳酸质量分析表明，电渗析液中氯离子含量较高。因此需要进一步纯化才能得到各种用途的乳酸。更多还原

【Abstract】 Lactic acid is an important organic acid with wide uses, especially in synthesis of biodegradable materials poly(lactic acid). Currently, the lactic acid recovery process is disadvantageous in terms of elaborate recovery process, exhausting a large amount of raw materials and waste production. To avoid such problems, this research is focused on conversion of lactate salts into lactic acid by electrodialysis using either bipolar or ion exchange membranes. The major advantages of this technology are high recovery efficiency, low energy consumption and having great potential in industrial production. The main goal of this work was to determine the suitable conditions for recovery of lactic acid from model sodium lactate by bipolar or ion exchange membrane electrodialysis, and from calcium lactate in model solution and fermentation broth by ion exchange membrane electrodialysis, and to evaluate the quality of lactic acid produced.In the bipolar membrane electrodialysis(BMED) operation, sodium lactate was converted into lactic acid and sodium hydroxide of high purity was obtained. The yield of lactic acid could exceed 90%, the current efficiency was about 60% and the electric energy consumption was between 2.5-3.5kWh/kg at 95% conversion factor of sodium lactate. During this study, the performance of bipolar membrane made in Beijing and cation membrane JCM-I was better. Current densities, initial concentration of sodium lactate and sodium hydroxide had great influence on the process. During batch operation, the optimal conditions were as follows: electric current was set at 2.5A, and initial concentrations of sodium lactate were 0.70 and 0.10mol/L, respectively.In the process of ion exchange membrane electrodialysis with three compartments, sodium lactate was converted into lactic acid and sodium sulphate was obtained by adding sulphuric acid. Under the conditions of this experiment, the yield of lactic acid and current efficiency exceeded 90%, and the energy consumption was about 0.7kWh/kg. During the process, high initial concentration of sodium lactate had更多还原