Abstract: Migration of amino acids concurrently with lactic acid from the feed cell to the acid cell in the three-compartment bipolar-membrane electrodialysis (BMED) process of lactic acid fermentation broth influences the purity of recovered lactic acid. Amino acid migration phenomenon and its rules were investigated in the bipolar-membrane electrodialysis process of lactic acid fermentation broth. The results showed that migration velocity of amino acid was mainly influenced by amino acid concentration, the difference between its pI and the environmental pH, the selectivity of anion exchange membrane to the amino acid anion, and the ionic mobility of amino acid anion. Based on this migration rule, an ionic migration velocity calculation model was developed and validated by comparing it with practical BMED process. The result of a process applying the calculation model showed that migration rate of total amino acids being 32.5% was 60.7% lower than the controlled experiment of 82.6%. Higher lactic acid purity via BMED could be achieved by regulating hydrogen leakage to control the pH in the feed cell and improving the selectivity of anion exchange membrane to lactic acid anion.

Key words: bipolar-membrane electrodialysis, lactic acid, amino acids, ionic migration, migration mechanism

摘要： 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.

关键词: 三室双极膜电渗析, 乳酸, 氨基酸, 离子迁移, 迁移规律