Mass transfer dynamics in the separation of phenol from model oil with quaternary ammonium salts via forming deep eutectic solvents

The separation of phenols from oil mixtures with quaternary ammonium salts (QASs) via forming deep eutectic solvents (DESs) is efficient, which avoids using alkali and acid and producing phenol-contained wastewater. In order to understand deeply the extraction process, the extraction kinetics of phenol in a model oil/DES system was studied using a constant-interface Lewis cell technique. The mass transfer coefficients and extraction rates of phenol were determined and the effects of stirring rate, temperature, specific area and QASs on the extraction were investigated. The results show that when using choline chloride as extractant, the extraction rate and mass transfer coefficient of phenol increase with increases of stirring rate and temperature. In the extraction process, the apparent active energy is 8.85 kJ mol−1. The mass transfer of phenol is controlled by diffusion, and the phenol diffusion in the DES phase is the slow extraction rate-determining step.