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Extraction of Amphoteric Amino Acid by Bipolar Membrane Electrodialysis: Methionine Acid as a Case Study

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journal contribution
posted on 23.02.2016, 00:00 by Xi Lin, Jiefeng Pan, Mali Zhou, Yanqing Xu, Jiuyang Lin, Jiangnan Shen, Congjie Gao, Bart Van der Bruggen
Methionine is an important amino acid to block the autophagy in cells. In industry, the production of methionine through the hydantoin pathway generates a huge amount of inorganic salts (i.e., Na2SO4), reducing the product purity. In this work, an efficient bipolar membrane electrodialysis (BMED) technology was proposed to extract high-purity methionine from the mother liquor of reaction. Lab-scale experiments were conducted with an optimized BMED stack at a current density of 150 A/m2. The energy consumption and current efficiency were acceptable, reaching 2.156 kWh/kg NaOH and 75.10%, respectively. Specifically, the base, i.e., NaOH, with a high concentration generated in BMED stack can be used for effective adsorption of H2CO3, in view of reducing the emission of CO2. Furthermore, a simulation of cation migration during the BMED operation was performed on the basis of the relationship between pH and the concentration of different ion species. From the simulation, it is critical to control the pH at ∼4.4 to maximize the purity and reduce the extraneous loss for methionine. Finally, a pilot-scale experiment was designed to evaluate the economic feasibility of BMED for the production of methionine. It can be confirmed that total cost of BMED operation for the production of methionine with high purity (99.4%) was estimated to be 321 $/t Met, which is economically viable in industry.