Harnessing fluoride-induced hydration dynamics for ultra-selective bioalcohol separation

Abstract

A salt-induced biphasic separation strategy utilizing potassium fluoride (KF) was developed for the efficient, green, and cost-effective recovery of biobutanol and bioethanol from concentrated acetone/n-butanol/ethanol (ABE) fermentation broth. Liquid–liquid equilibrium data demonstrated KF’s exceptional salting-out performance: at 500 g/kg addition, it achieved 99.17 % dehydration, 91.95 % ethanol recovery, and complete n-butanol recovery, outperforming other potassium halides and highly soluble strong base–weak acid salts. Across various test systems, such as 40 wt% ABE, 50 wt% ABE, 40 wt% acetone, 40 wt% n-butanol, 40 wt% ethanol, 12 wt% acetone, 24 wt% butanol, near-saturation KF levels consistently yielded > 98 % dehydration, >91 % ethanol recovery, and >99.8 % butanol recovery, confirming its superior adaptability and stability. Mechanistic insights revealed that KF disrupts water-organic azeotropes via F⁻-driven hydrolysis and intense hydration interactions, where its charge density and hydration enthalpy promote selective water binding and phase separation. Additionally, synergistic interactions between KF and both polar and non-polar ABE components were identified as key to enhanced separation. This study provides a robust theoretical and practical framework for next-generation salting out in biofuel purification.