Removal of chlorophenols from aqueous media with hydrophobic deep eutectic solvents: Experimental study and COSMO RS evaluation

Abstract Chlorophenols have been strongly linked with health and environmental risks which includes genotoxicity, mutagenicity, carcinogenicity and histopathological alterations. These hazards are further intensified due to the prevalent usage and disposal. Hence, regulatory bodies have established tolerable limits for chlorophenols in water and air. In this study, seven different hydrophobic deep eutectic solvents (HDESs) were prepared and characterized for the liquid extraction of 3-chlorophenol (3-CP), 2-chlorophenol (2-CP) and 2,4-dichlorophenol (2,4-DCP) form wastewater. The HDESs are Menthol-Hexanoic acid 1:2, Menthol-Octanoic acid 1:2, Menthol-Decanoic acid 1:2, and Menthol-Thymol 1:1, 1:2, 1:3, 1:4. To the best of our knowledge, this is the first study to focus on the extraction of 3-chlorophenols and 2,4-dichlorophenols with these seven HDESs. The effect of different conditions such as pH (3−11), initial concentration in aqueous solution (0-1000 ppm) and the HDES/water mass ratio (1:1–1:10) on the extraction efficiency of the chlorophenols was evaluated. The experimental results showed that the HDESs have excellent extraction capacity for the chlorophenols which were studied. The extraction efficiencies were higher than 94% under the conditions investigated. The extraction capacity of the chlorophenols followed the order 3-CP > 2-CP > 2,4-DCP for the Menthol-Alkanoic acid HDESs. In addition, Conductor-like Screening Model for Real Solvents (COSMO-RS) was utilized to model the extraction process. This model provides insightful understanding of the interaction between the HDESs and the chlorophenols. In general, the COSMO RS provided good agreement with the experimental data.