Multistage Fractionation of Polycyclic Aromatic Hydrocarbon Isomers Using a Deep Eutectic Solvent-Based Aqueous Three-Phase System

This study demonstrates an innovative multiple-stage separation strategy for anthracene and phenanthrene by using a deep eutectic solvent (DES)-based aqueous three-phase system (ATrPS). The system, composed of choline chloride–PEG400–glycerol DES (1:1:1 molar ratio) and K2HPO4, achieved good separation efficiency through three key mechanisms: DES-mediated polarity adjustment of phase environments, salt-induced phase boundary modification, and multistage fractionation amplification. The optimal system (70.0 wt % DES + 17.5 wt % K2HPO4) showed superior performance with an initial selectivity of 1.21 ± 0.05, which increased to 2.44 ± 0.05 after three extraction stages, representing a 2.22-fold enhancement over aqueous two-phase systems composed of 55.0 wt % DES and 17.5 wt % K2HPO4. The DES’s tunable physicochemical properties, coupled with K2HPO4’s salting-out effect, created an ideal environment for isomer discrimination. This green separation platform offers significant advantages for challenging separations in pharmaceutical and petrochemical applications.