Hydrogen bond basicity of ionic liquids and molar entropy of hydration of salts as major descriptors in the formation of aqueous biphasic systems

Abstract

Aqueous biphasic systems (ABS) composed of ionic liquids (ILs) and conventional salts have been largely investigated and successfully used in separation processes, for which the determination of the corresponding ternary phase diagrams is a prerequisite. However, due the large number of ILs that can be prepared and their high structural versatility, it is impossible to experimentally cover and characterize all possible combinations of ILs and salts that may form ABS. The development of tools for the prediction and design of IL-based ABS is thus a crucial requirement. Based on a large compilation of experimental data, a correlation describing the formation of IL-based ABS is shown here, based on the hydrogen-bonding interaction energies of ILs (EHB) obtained by the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) and the molar entropy of hydration of the salt ions. The ability of the proposed model to predict the formation of novel IL-based ABS is further ascertained.

Effect of Ionic Composition on Physicochemical Properties of Mono-Ether Functional Ionic Liquids

“…ILs with the same anion ([NTf 2 ] − ) showed a general trend that a longer alkyl chain substitution (at the 1 or 3 positions) on the imidazolium ring tend to have lower thermal stability than shorter alkyl chain substituted analogues. Moreover, anions also play a significant role in affecting the thermal stability of ME-FILs in the order of decomposition temperatures: [NTf 2 ] − > [PF 6 ] − > [BF 4 ] − , which is consistent with the density trend (ME-FIL 2 > ME-FIL 7 > ME-FIL 6 ), and the thermal decomposition temperature T d = 430 °C of ME-FIL 2 is near to [BMIm][NTf 2 ] (421 °C) [41,42], which has a similar structure to ME-FIL 2 but without ether functionalization. The higher thermal stability of ME-FILs with [NTf 2 ] − may be attributed to stronger Van Der Waals forces between the cation and anion [43].…”

Synthesis of Purine-Based Ionic Liquids and Their Applications

“…The same does not apply for [N 4444 ][Theob] binodal curves, with Na 2 SO 4 being a better ABS promoter than K 3 C 6 H 5 O 7 . This change in tendency was also observed with other ILs [67]. Take the formation of ABS with [N 4444 ]Cl/[N 4444 ]Br and Na 2 SO 4 /K 3 C 6 H 5 O 7 as an example, for which the K 3 C 6 H 5 O 7 salt ability to form ABS with [N 4444 ]Br is slightly better than the one reported for Na 2 SO 4 [68].…”

“…Take the formation of ABS with [N4444]Cl/[N4444]Br and Na2SO4/K3C6H5O7 as an example, for which the K3C6H5O7 salt ability to form ABS with [N4444]Br is slightly better than the one reported for Na2SO4 [68]. However, the anion change from bromide to chloride leads to the modification of this tendency, with K3C6H5O7 being a stronger salting-out agent than Na2SO4 [67,68]. Overall, the salt seems to have a small impact on the binodal curves, under the tested conditions.…”

Extraction and Stabilization of Betalains from Beetroot (Beta vulgaris) Wastes Using Deep Eutectic Solvents

“…Their use have numerous environmental advantages; they are ecologically friendly [9] and have a bright future in terms of their application in separating and recovering high-value products in process industries [10], mostly for the isolation and recovery of functional molecules (terpenoids, carotenoids, and flavonoids) from plants, fruit, and vegetables, with optimal results [11,12]. Mainly, extraction techniques and the optimization of process conditions by DES, including an economic analysis of DES usage as extractive agents are available [13]. However, the research on this topic is recent; therefore, there are still many aspects to resolve.…”

“…However, the research on this topic is recent; therefore, there are still many aspects to resolve. The recovery of extracted compounds and DES solvents as well as DES recyclability for their reuse are the most important challenges [13,14].…”