Extraction of halogenated hydrocarbons using hydrophobic ionic liquids

Halogenated hydrocarbons (HHCs) are members of priority water pollutants due to their adverse health and environmental impacts and their removal from water is of paramount importance. In this research, six different types of hydrophobic ionic liquids (ILs) were evaluated for the extraction of three HHCs from water, namely carbon tetrachloride (CCl4), chloroform (CHCl3), and bromoform (CHBr3). The ILs were selected based on their: (i) affinity to solubilize contaminants of concern, (ii) moderate viscosity, (iii) hydrophobicity, and (iv) stability in the presence of the superoxide ion that will be used for the destruction of HHCs. The selected ILs successfully removed HHCs from water with extraction efficiencies ranging from 83% to 99%. It was found that octyltriethyl-ammonium and -pyrrolidinium cation paired with bis (trifluoromethylsulfonyl) imide [Tf2N] anion exhibit high performance for extracting CCl4, CHCl3, and CHBr3. The effect of process parameters, including contact time, temperature, pH, hydrogen bond donor (α), hydrogen bond acceptor (β), dipolarity/polarizability (π∗), and octanol/water partition coefficient (Kow) on the extraction efficiency were also investigated. It was also found that optimal extraction efficiency was achieved within 5 min contact time. The study found selected ILs can be effectively used for water and wastewater treatment. The extraction of HHCs through ILs can also be used as a potential analytical approach for the identification of HHCs in water by chromatography technique.