The Hydrogen Bond-Driven Mechanism for Carbazole Extraction: Experimental and Theoretical Analysis of Alcohol-Based Deep Eutectic Solvents

This study presents an efficient and eco-friendly approach to extracting carbazole from anthracene oil using deep eutectic solvents (DESs), leveraging the hydrogen bond-driven mechanism. Four DESs, synthesized from tetraethylammonium chloride and alcohols with varying chain lengths, were evaluated for their extraction performance. Experimental findings indicate that the DES containing pentanediol achieved the highest extraction rate of 97.35 % under optimal conditions and also showed promising results in real coal tar extraction. Molecular dynamics simulations and density functional theory analyses confirmed that hydrogen bonds, particularly multicenter N-H···O and N-H···Cl interactions, were the main force enhancing the selective extraction of carbazole. Fourier transform infrared spectroscopy validated the theoretical insights, providing evidence of hydrogen bond formation between DESs and carbazole. This study's insights into the role of hydrogen bonding in DES-mediated extraction processes offer a sustainable strategy for the purification of valuable compounds from complex mixtures.