LCST-Type Phase Behavior of Aqueous Biphasic Systems Composed of Phosphonium-Based Ionic Liquids and Potassium Phosphate

Abstract

Although aqueous biphasic systems (ABS) composed of phosphonium-based ionic liquids (ILs) have demonstrated superior performance as viable media for biocompatible extraction processes, the formation of ABS with tetrabutylphosphonium trifluoroacetate ([P 4444 ]CF 3 COO) and tributyloctylphosphonium bromide ([P 4448 ]Br) were seldom investigated. To evaluate the hydrophilicity of [P 4444 ]CF 3 COO and [P 4448 ]Br, the solubility curves for the mixture of the ILs and water were determined. The influence of temperature on the phase behavior for the [P 4448 ]Br + K 3 PO 4 + H 2 O and [P 4444 ] CF 3 COO + K 3 PO 4 + H 2 O systems were also obtained. Results show that both [P 4448 ]Br + H 2 O and [P 4444 ]CF 3 COO + H 2 O binary systems undergo lower critical solution temperature-type phase transition, and the ABS composed of [P 4444 ]CF 3 COO and [P 4448 ]Br can be formed with K 3 PO 4 at a wide range of temperatures. Moreover, the ABS are highly temperature dependent, and biphasic region expands with an increase in temperature. On the other hand, the capability of the ILs to induce ABS follows the tread [P 4448 ]Br > [P 4444 ]CF 3 COO. This suggests that the lower cation hydrophilicity of ILs results in greater biphasic area in the ABS formed by phosphonium-based ILs.

Utilization of inorganic salts as adjuvants for ionic liquid–water pretreatment of lignocellulosic biomass: enzymatic hydrolysis and ionic liquid recycle

“…Subsequently, we carried out repetitive drop-wise addition of the aqueous inorganic salt solution to each IL aqueous solution until the detection of a cloudy and further biphasic solution, followed by the drop-wise addition of ultrapure water until a monophasic region is detected. Further details on the experimental procedure can be found elsewhere (Gao et al 2017;Louros et al 2010). The compositions were determined by the weight quantification of all components.…”

Thermoseparative Regeneration of Triblock Copolymer after Aqueous Biphasic Extraction of Molybdate Species

“…From Figure 1, it is clear that the biphasic region increases with increase in temperature which is in agreement with the facts observed and reported earlier. 40 This observation can be explained on the basis of decreased solubility of the copolymer and increased solubility of the salt with increase in temperature. The binodal curve shifts toward the left as temperature Table 1.…”

Thermoresponsive Ionic Liquid/Water Mixtures: From Nanostructuring to Phase Separation

“…The approach of inducing demixing by adding a suitable third species, sometimes represented by relatively simple inorganic salts, has also been used in IL/water solution. The primary aim of the approach has been to create new stable IL and water biphasic systems [ 134 , 135 ], the side result, however, has been to make thermoresponsive even water solutions of hydrophilic ILs that are fully soluble in the binary phase [ 136 ]. In all of these cases, the decreased stability of the IL/water solution has been obtained by resorting to inorganic systems, such as K PO , having a strong water structuring (kosmotropic) effect, resulting in the salting out of the organic IL.…”