Solvent extraction of selected endocrine-disrupting phenols using ionic liquids

In this paper, investigations have been carried out to determine the suitability of imidazolium-based ionic liquids (ILs), 1-methyl-3-alkylimidazolium hexafluorophosphate [Cnmim][PF6] (n = 4, 6, 8) and 1-methy-3-alkylimidazolium tetrafluoroborate [Cnmim][BF4] (n = 6, 8), in replacing volatile organic solvents for liquid–liquid extraction of selected endocrine-disrupting phenols from aqueous solutions. New experimental data have been reported for the extraction of phenol, bisphenol A, pentachlorophenol, 4-octylphenol and 4-nonylphenol by the ILs. The results showed that distribution ratios of the endocrine-disrupting phenols were influenced significantly by pH of the aqueous phase, nature of the ILs, chemical structure of the phenols, and the presence of some salts in aqueous solutions. It was found that in the range of pH <7, most of the phenols were extracted quantitatively from aqueous solution into the ILs. The selective separation of some of the phenols from their binary mixtures was also investigated, and the possible driven forces for the extraction were discussed based on the hydrogen-bonding and hydrophobic interactions between the ILs and the phenols. It is expected that these results are promising for the liquid–liquid extraction, separation and preconcentration of endocrine-disrupting phenols in analytical science and related industrial process.