How to apply terpenoid-based deep eutectic solvents for removal of antibiotics and dyes from water: Theoretical prediction, experimental validation and quantum chemical evaluation

This study proposed a theoretical prediction method and mechanism investigation for the extraction of antibi-otics and dyes from aqueous media using terpenoid-based deep eutectic solvents (DESs). Firstly, Conductor-like Screening Model for Real Solvents (COSMO-RS) approach was applied to predict selectivity, capacity and per-formance index in the extraction of 15 target compounds including antibiotics (tetracyclines, sulfonamides, quinolones, beta-lactams) and dyes by 26 terpenoid-based DESs, and thymol-benzyl alcohol shows promising theoretical selectivity and extraction efficiency for the target compounds. Moreover, the structures of both hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) have an impact on the predicted extraction performance, which can be improved by tailoring those candidates with higher polarity, smaller molecular volume, shorter alkyl chain length and the presence of aromatic ring structures, etc. According to the predicted molecular interactions revealed by sigma-profile and sigma-potential, the DESs with HBD ability can promote the sepa-ration process. Furthermore, reliability of proposed prediction method was confirmed by experimental verifi-cation, indicating that the trends of theoretical extraction performance index were similar with the experimental results by using actual samples. At last, the extraction mechanism was evaluated by quantum chemical calcu-lations based on visual presentations, thermodynamic calculations and topological properties; and the target compounds showed favorable energies of solvation to transfer from aqueous phase to DESs phase. The proposed method has been proved with potential to provide the efficient strategies and guidance for more applications (e. g., microextraction, solid phase extraction, adsorption) with similar molecular interactions of green solvents in environmental research.

Automated summary

This study proposed a theoretical prediction method and mechanism investigation for the extraction of antibiotics and dyes using terpenoid-based deep eutectic solvents. A COSMO-RS approach was applied to predict selectivity, capacity, and performance index, and thymol-benzyl alcohol showed promising theoretical selectivity and extraction efficiency for the target compounds. The structures of hydrogen bond acceptors and donors also had an impact on the extraction performance.