Liquid–Liquid Equilibria in Aqueous 1-Alkyl-3-methylimidazolium- and 1-Butyl-3-ethylimidazolium-Based Ionic Liquids

Abstract

In this work, novel phase diagrams for aqueous solutions of 1-alkyl-3-methylimidazolium-and 1-butyl-3-ethylimidazolium-based ILs combined with phosphate-based salts, namely, K 3 PO 4 or K 2 HPO 4 , are reported and discussed. To correlate the binodal data, the Merchuk equation is applied. The tie lines and tie-line lengths are also presented. The anion influence on the ability to form aqueous biphasic system (ABS) is investigated for the IL with the same1-butyl-3-methylimidazolium cation, [bmim] + , and various anions, for example, salicylate, [SAL] − ; trifluoromethanesulfonate, [TFS] − ; dicyanamide, [DCA] − ; and chloride, [Cl] − . The order of studied anions to form ABS is [TFS]The effect of alkyl chain length on imidazolium ion on liquid− liquid equilibrium is discussed in terms of increasing ionic liquid hydrophobicity and poorer affinity for water. It is shown that 1-hexyl-3-methylimidazolium chloride ionic liquid has a better ability to form ABS comparing to ionic liquid with butyl chain and the same anion. Newly synthesized ionic-liquidcontaining ethyl group 1-butyl-3-ethylimidazolium bromide was also investigated, showing the influence of both ethyl group and bromide anion on the ability of ABS formation. ■ INTRODUCTIONIonic liquids (ILs) are the salts with melting point lower than 373.15 K showing low toxicity, biodegradability, a negligible vapor pressure, high conductivity and thermal stability. 1 Such unique properties make them alternative solvents for toxic volatile organic compounds. Due to their tunable physical and chemical properties, they are called designed solvents and can be applied in many industrial and technological processes, as well in analytical separation techniques. 2−8 Recently, the newest generation of ILs with targeted biological properties containing biologically active components extends the sphere of their use in pharmacy, medicine, and agriculture as potential drugs. 9−17 Liquid−liquid extraction based on ionic liquids and waterstructuring salts as aqueous biphasic systems have been reported for the first time in 2003. 18 These systems have been successfully used to separate drugs, 19−22 proteins, 23 dyes, 24 and pesticides. 25 Liquid−liquid equilibrium (LLE) data at different temperatures and compositions are essential for the optimization of extraction process using ABS. For this purpose, water-soluble hydrophilic ionic liquids can be used as extracting solvent, as they induce formation of aqueous biphasic systems with suitable kosmotropic agents forming a new type of partitioning systems. 18,26,27 Such ABS with the right proportions of ionic liquid and kosmotropic salt can be used as an alternative extraction medium to conventional systems of either liquid−liquid or liquid−solid type.Contrary to previous reports that hydrophilic ionic liquids are structure breakers or "chaotropes", 28−31 kosmotropic properties of many imidazolium-based ILs containing different anions such as halide, dicyanamide or salicylate were reported. 32−34 It was described that these ILs strongly in...

Anticancer and antimicrobial properties of imidazolium based ionic liquids with salicylate anion

“…Among them was 1-butyl-3-methylimidazolium salicylate (1), a salicilyte analogue of the well-known BMIM + cation-based ionic liquid, which expresses very good physicochemical properties and, accordingly, has a wide range of applications. [27][28][29] Compared to compound 1 that possesses a non-polar n-butyl substituent at N-1, ILs with more polar substituents (compounds 2-5) showed lower general toxicity (Table II). 12 In this study, the effect of imidazolium based ILs with salicylate anion 1-4 and salts 5 and 6 was tested against human cancer cell lines, as well as against selected bacteria or fungal strains.…”

Improved single-step extraction performance of aqueous biphasic systems using novel symmetric ionic liquids for the decolorisation of toxic dye effluents

“…The biphasic phase diagrams were determined applying the cloud point titration method at room temperature (296.15 ± 1 K) and atmospheric pressure (0.1 MPa) [33,[36][37][38]. The aqueous solution of inorganic salt ( = 50%) was added drop by drop to the aqueous solution of IL ( = 60%) of known mass until the mixture become cloudy.…”

Ionic Liquid–Liquid Chromatography: A New General Purpose Separation Methodology

“…This information is useful in ionic liquid–liquid chromatography and demonstrates how the design of an ionic liquid affects the distribution ratios of solutes. A number of reviews [ 115 , 130 – 133 ] and further information on the liquid–liquid equilibria of ionic liquids have been published elsewhere.

Fig.

…”