Separation of phenol from model oils with quaternary ammonium saltsvia forming deep eutectic solvents

A variety of quaternary ammonium salts have been used to efficiently separate phenols from model oils, which avoids the use of mineral alkali and acids that produce phenol-containing waste water. It was found that some quaternary ammonium salts showed high phenol-removal efficiencies, which could reach as high as 99.9%. The separation mechanism was also discussed.