Abstract
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 (CnC1im C1SO4, n = 2 and 4), tributylmethyl phosphonium methylsulfate (P4441 C1SO4) and methylpyridinium methylsulfate (C1Py C1SO4) and two high charge density potassium inorganic salts (K2CO3 and K2HPO4) 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.
Highlights
Organochlorine micropollutants such as insecticides are the subject of a great environmental and health concern since they remain in soils without significant degradation up to 30 years after their use
The experimental binodal curves for the ternary mixtures composed of aqueous solutions of the ionic liquids (ILs) (CnC1im C1SO4, n = 2 and 4, P4441 C1SO4 and C1Py C1SO4) and inorganic salts (K2CO3 and K2HPO4)
The information coming from the literature [29] indicates that just experimental data related to the system composed of C2C1im C1SO4 and K2HPO4 are available and a very good agreement is obtained
Summary
Organochlorine micropollutants such as insecticides (lindane, heptachlor, DDT, etc.) are the subject of a great environmental and health concern since they remain in soils without significant degradation up to 30 years after their use. Pentachlorophenol (PCP) is considered as an outstanding example, since it has been used in ropes, paints adhesives, brick walls, and especially as fungicide and insecticide for wood preservation. About 36 million PCP-treated utility pine poles are in service across the United States [1], which poses an undoubted environmental risk. The need to investigate efficient remediation techniques for the removal of this kind of pollutants has furthered the emergence of physico-chemical (chemical precipitation, lime coagulation, ion exchange, reverse osmosis, volatilization, photolysis, and adsorption) or biological (biosorption or biodegradation) techniques. These methods present several shortcomings such as incomplete removal, sludge generation, time and energy requirements or high operating costs [3]
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