Liquid Extraction of Chlorophenols from Wastewater with Hydrophobic Deep Eutectic Solvents

Chlorophenols are associated with a number of environmental and health hazards such as mutagenicity, histopathological alterations, genotoxicity and carcinogenicity. These associated risks coupled with their widespread utilization and disposal has driven regulatory bodies to set acceptable limits to their presence in air and water bodies. In this work, seven different hydrophobic deep eutectic solvents (DESs) were synthesized and characterized for the liquid–liquid extraction of 2-chlorophenol, 3-chlorophenol and 2,4-dichlorophenol from wastewater. The hydrophobic DESs studied include Menthol-Thymol 1:1-4, Menthol-Hexanoic acid 1:2, Menthol-Octanoic acid 1:2 and Menthol-Decanoic acid 1:2. The effect of different conditions such as pH, initial concentration of aqueous solution and the phase ratio on the extraction efficiency of the chlorophenols was evaluated. Moreover, Conductor-like Screening Model for Real Solvents (COSMO-RS) was used to model the extraction process. This model provides insightful understanding of the interaction between the hydrophobic DESs and the chlorophenols. The experimental results showed that the hydrophobic DESs have high extraction capacity for the chlorophenols which were studied. The extraction efficiency was more than 94% under the conditions investigated. In addition, the COSMO RS provided good agreement with the experimental data.