Efficient extraction of phenol from oil using halogen-free deep eutectic solvents: experimental investigation and computational analysis

Phenolics are high added value materials mainly gained from coal tar and coal liquefaction oil. Present study systematically investigated new halogen-free betaine-glycolic acid and betaine-glycolic acid-ethylene glycol deep eutectic solvents (DESs) as extractants of phenol from model oil, including the influence of DES composition, DESs/oil mass ratio, extraction time, temperature, and initial phenol concentration on the extraction performances. The preferred betaine-glycolic acid-ethylene glycol (1:1:1) demonstrated the extraction efficiency of 96.5% and the toluene entrainment of 6.9%. Meanwhile, FT-IR, quantum chemistry (QC), and molecular dynamics (MD) mutually confirmed that the extraction was governed by hydrogen bonding and van der Waals forces between DESs and phenolics. These DESs demonstrated potential application in separating phenolics from oils due to their good and reversible extraction ability.