Remarkable chlorobenzene absorption by carboxylic acid based deep eutectic solvents

A novel purification technology for the absorption of chlorobenzene (CB) using carboxylic acid based deep eutectic solvents (DESs) as absorbents was proposed and systematically investigated, combining experiments with microscopic molecular simulations. A series of newly designed DESs synthesized and evaluated for their CB absorption performance, revealing that DESs with quaternary phosphonate as hydrogen bond acceptors (HBAs) and long-chain fatty acid-based hydrogen bond donors (HBDs) exhibit remarkable CB absorption performance. Additionally, it illustrated that both the structure and acidity of HBD significantly impact the absorption capacity. Consequently, the DES comprising tetrabutylphosphonium chloride ([P4444][Cl]) and decanoic acid (DecA) with molar ratio of 1:2 was identified as the possessing optimal absorbent. Notably, after undergoing five cycles of absorption-desorption processes, the CB absorption capacity in [P4444][Cl]-DceA (1:2) was almost maintained at approximately 467 mg/g (Henry's law constant of 4.90Pa m3/mol) at 30 degrees C. NMR characterization revealed no chemical bonding between [P4444][Cl]-DceA and CB, indicating that it's a physical absorption process. Finally, the interaction mechanism was elucidated by COSMO-RS model, quantum chemical calculations and wave function analysis. This work fills the gap of CB removal by DES absorption and proves that DES is a promising green solvent for the removal of chlorinated volatile organic compounds.