Pesticide Removal from Aqueous Solutions by Adding Salting Out Agents

Phase segregation in aqueous biphasic systems (ABS) composed of four hydrophilic ionic liquids (ILs): 1-butyl-3-methylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium methylsulfate (C(n)C(1)im C(1)SO(4), n = 2 and 4), tributylmethyl phosphonium methylsulfate (P(4441) C(1)SO(4)) and methylpyridinium methylsulfate (C(1)Py C(1)SO(4)) and two high charge density potassium inorganic salts (K(2)CO(3) and K(2)HPO(4)) were determined by the cloud point method at 298.15 K. The influence of the addition of the selected inorganic salts to aqueous mixtures of ILs was discussed in the light of the Hofmeister series and in terms of molar Gibbs free energy of hydration. The effect of the alkyl chain length of the cation on the methylsulfate-based ILs has been investigated. All the solubility data were satisfactorily correlated to several empirical equations. A pesticide (pentachlorophenol, PCP) extraction process based on the inorganic salt providing a greater salting out effect was tackled. The viability of the proposed process was analyzed in terms of partition coefficients and extraction efficiencies.