Skip to Content
Merck
  • Effect of salts on the solubility of ionic liquids in water: experimental and electrolyte Perturbed-Chain Statistical Associating Fluid Theory.

Effect of salts on the solubility of ionic liquids in water: experimental and electrolyte Perturbed-Chain Statistical Associating Fluid Theory.

Physical chemistry chemical physics : PCCP (2015-11-18)
Catarina M S S Neves, Christoph Held, Sultan Mohammad, Miko Schleinitz, João A P Coutinhoa, Mara G Freire
ABSTRACT

Due to scarce available experimental data, as well as due to the absence of predictive models, the influence of salts on the solubility of ionic liquids (ILs) in water is still poorly understood. To this end, this work addresses the solubility of the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4C1im][NTf2]), at 298.15 K and 0.1 MPa, in aqueous salt solutions (from 0.1 to 1.5 mol kg(-1)). At salt molalities higher than 0.2 mol kg(-1), all salts caused salting-out of [C4C1im][NTf2] from aqueous solution with their strength decreasing in the following order: Al2(SO4)3 > ZnSO4 > K3C6H5O7 > KNaC4H4O6 > K3PO4 > Mg(CH3CO2)2 > K2HPO4 > MgSO4 > KH2PO4 > KCH3CO2. Some of these salts lead however to the salting-in of [C4C1im][NTf2] in aqueous medium at salt molalities lower than 0.2 mol kg(-1). To attempt the development of a model able to describe the salt effects, comprising both the salting-in and salting-out phenomena observed, the electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was applied using ion-specific parameters. The gathered experimental data was modelled using ePC-SAFT parameters complemented by fitting a single binary parameter between K(+) and the IL-ions to the IL solubility in K3PO4 aqueous solutions. Based on this approach, the description of anion-specific salting-out effects of the remaining potassium salts was found to be in good agreement with experimental data. Remarkably, ePC-SAFT is even able to predict the salting-in effect induced by K2HPO4, based on the single K(+)/IL-ions binary parameter which was fitted to an exclusively salting-out effect promoted by K3PO4. Finally, ePC-SAFT was applied to predict the influence of other sodium salts on the [C4C1im][NTf2] solubility in water, with experimental data taken from literature, leading to an excellent description of the liquid-liquid phase behaviour.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Potassium sodium tartrate tetrahydrate, puriss., 99.0-101.0% (calc. on H2O free substance), meets analytical specification of Ph. Eur., BP, USP, FC, E 337
Sigma-Aldrich
Potassium sodium tartrate tetrahydrate, ACS reagent, 99%
Sigma-Aldrich
Water, deuterium-depleted, ≤1 ppm (Deuterium oxide)
Sigma-Aldrich
Potassium sodium tartrate tetrahydrate, BioUltra, ≥99.5% (NT)
Sigma-Aldrich
Water, for cell biology, sterile ultrafiltered
Sigma-Aldrich
Water, for molecular biology, sterile filtered
Sigma-Aldrich
Magnesium sulfate heptahydrate, BioXtra, ≥99.0%
Sigma-Aldrich
Water, PCR Reagent
Sigma-Aldrich
E-Toxate Water, endotoxin, free
Sigma-Aldrich
Potassium sodium tartrate tetrahydrate, ReagentPlus®, ≥99%
Sigma-Aldrich
Water, for embryo transfer, sterile-filtered, BioXtra, suitable for mouse embryo cell culture
Sigma-Aldrich
Potassium phosphate tribasic, reagent grade, ≥98%
Sigma-Aldrich
Magnesium sulfate heptahydrate, BioReagent, for molecular biology, suitable for plant cell culture, ≥99.0%
Sigma-Aldrich
Water, BioPerformance Certified
Sigma-Aldrich
Potassium acetate solution, BioUltra, for molecular biology, 5 M in H2O
Sigma-Aldrich
Magnesium sulfate heptahydrate, BioUltra, ≥99.5% (KT)
Sigma-Aldrich
Water, Nuclease-Free Water, for Molecular Biology
Sigma-Aldrich
Aluminum sulfate, 99.99% trace metals basis
Sigma-Aldrich
Water, sterile-filtered, BioReagent, suitable for cell culture
Sigma-Aldrich
Potassium sodium tartrate tetrahydrate, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.5% (perchloric acid titration)
Sigma-Aldrich
Magnesium sulfate heptahydrate, 99.5-100.5% (calc. to the dried substance), meets analytical specification of Ph. Eur., BP,USP, FCC
Sigma-Aldrich
Magnesium sulfate heptahydrate, ReagentPlus®, ≥99.0%
Sigma-Aldrich
Magnesium sulfate heptahydrate, puriss. p.a., ACS reagent, ≥99.0% (KT)
Sigma-Aldrich
Magnesium sulfate heptahydrate, ACS reagent, ≥98%
Sigma-Aldrich
Water, ACS reagent
Sigma-Aldrich
Water, Deionized
Sigma-Aldrich
Potassium phosphate dibasic, 99.95% trace metals basis
Sigma-Aldrich
Potassium phosphate dibasic, anhydrous, for luminescence, for molecular biology, BioUltra, ≥99.0% (T)
Sigma-Aldrich
Potassium citrate tribasic monohydrate, purum p.a., ≥99.0% (NT)
Sigma-Aldrich
Potassium phosphate monobasic, 99.99% trace metals basis