High capacity, silica-based anion-exchange nanofiber membranes for the selective recovery of lactic acid

Fermentation processes offer a sustainable way for green organic acid production such as lactic acid (LA). However, the recovery and purification of LA from fermentation broths is typically very energy demanding. The in-situ recovery of LA via migration of its lactate anion through an anion-exchange membrane (AEM), combining electrochemical systems with fermentation, offers a viable solution for this. In this work, sustainable silica-based nanofiber AEMs were developed with excellent ionic properties and a strong selectivity for organic acids. Starting from a tetraethoxysilane/chloropropyltriethoxysilane (TEOS/CPTES) sol-gel system, anion conductive nanofiber membranes were obtained via the alkylation of the Csingle bondCl moieties on the electrospun nanofibers with 1-methylimidazole, resulting in an ion-exchange capacity (IEC) of 1.9 ± 0.3 mmol g−1. Post-functionalization with octyltriethoxysilane (OTES) resulted in hydrophobic porous nanofiber AEMs with excellent separation properties. It was shown that the nanofiber AEM had an improved lactate selectivity compared to a commercially dense AEM in the presence of (selectivity of 8.8 vs. 1.1) with an energy consumption of 1.6 kWh kg−1 vs. 3.0 kWh kg−1 for lactate migration, proving its potential as a sustainable material for industrial applications.