Conversion of S‑2-amino-1-butanol‑l‑tartrate to S‑2-amino-1-butanol by Using Bipolar Membrane Electrodialysis for Post-treatment of Direct Enantioseparation

In this work, a green route for the preparation of S-2-amino-1-butanol in the post-treatment for direct enantioseparation for the antituberculosis drug ethambutol hydrochloride has been explored. Therein, OH– produced from bipolar membrane electrodialysis (BMED) technology was used to in situ converse diastereomeric salt S-2-amino-1-butanol-l-tartrate to S-2-amino-1-butanol, rather than directly adding the chemical reagent of NaOH or Na2CO3 in a traditional way. For realization of the process, laboratory-scale BMEDs with two membrane stack configurations were fabricated, followed by an investigation of the effect of ion-exchange membrane types, initial feed concentrations, voltages, etc. As a result, under optimized conditions, the concentration of as-obtained S-2-amino-1-butanol (the final purity of the product: ca. 98.2%) can achieve 1.04 mol·L–1, and the conversion rate is 92.28%. The cost is estimated at approximately $2.22 kg–1. Accordingly, the current efficiency and energy consumption are 54.05% and 1.88 kW·h·kg–1, respectively. The investigation has verified the feasibility of BMED for the conversion of S-2-amino-1-butanol-l-tartrate to S-2-aminobutanol and also demonstrates potential application in the field of chiral compound separation.