Selective HCl Separation from HCl/SiF4 Mixtures via Glycerol-Based Absorption and Staged Vacuum Desorption

The selective removal of HCl from industrial HCl/SiF4 mixtures was investigated using a series of alcohol-based and deep eutectic solvents (DESs). Among them, glycerol (GL) exhibited superior selectivity for HCl despite a moderate total capacity. Absorption at 60 °C ensured stable operation with minimal foaming. Desorption analysis revealed that both HCl and SiF4 underwent partial irreversible absorption under N2 stripping, while staged vacuum desorption enabled efficient and selective recovery—SiF4 was fully removed at 70 °C and 6 kPa, followed by nearly complete HCl desorption at 90 °C. Cyclic tests confirmed excellent solvent stability and rapid regeneration, with complete desorption achieved within 10–15 min. A conceptual process was proposed based on these findings, demonstrating a practical and energy-efficient route for selective HCl recovery from acid–gas mixtures.