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Aiming at developing more biocompatible and economic separation platforms, aqueous biphasic systems (ABS) composed of deep eutectic solvents (DES) and tert-butanol were proposed for the first time. The effects of key factors such as the hydrogen-bond donor (HBD) properties and temperature on the phase-forming ability of DES/tert-butanol ABS were investigated. Meanwhile, syringic acid and eugenol mixtures were selected as model biomolecules to evaluate the efficiency of DES/tert-butanol ABS to use as liquid−liquid extraction systems. The results indicated that DES components migrated preferentially to the bottom phase while tert-butanol was concentrated in the top phase. The more hydrophilic HBD or lower temperature was responsible for greater efficiency to induce the formation of DES/tert-butanol ABS. The reason for phase separation was the incompatibility of the hydrogen-bond acceptor (HBA) and HBD with tert-butanol in aqueous solution, where the higher hydrophilic HBD enriched favorably in the lower phase, allowing for the formation of the DES/tert-butanol ABS. The selective separation of syringic acid and eugenol was a consequence of the HBD characters, temperature, and tie-lines length of the ABS, and they could be greatly separated by using the ABS composed of betaine-xylitol (DES) and tert-butanol at 298.15 K. The highest extraction efficiency of syringic acid and eugenol was 91.64 and 97.62%, respectively. Further, syringic acid and eugenol as well as DES can be recovered and reused by using water as the antisolvent and the vacuum distillation method. This study may be expected to lay a solid foundation for the expansion of DES-based ABS and selective separation of similar biomolecules.

The reason for the formation of an anhydrous and surfactant-free deep eutectic solvent (DES)-based microemulsion system has been widely explored so far. Dissipative dynamism (DPD) is used to simulate the composition of DES, diethyl adipate (Da), and tetrahydrofurfuryl alcohol (THFA) systems to study their emulsification mechanism and quantitative properties. The influence of the proportions of different DES, Da, and THFA components on the phase formation of microemulsion was discussed through simulations. The radial distribution function, diffusion coefficient, interaction energy, and order parameters are calculated from the simulation results, and the mesoscopic properties and the driving force of emulsification formation are analyzed through these quantitative data. In addition, the calculated results of the DPD simulation method of this subject are in good agreement with the experimental results. Therefore, the DPD method can be used to understand the mechanism of phase formation and predict the emulsification ability of different components, which is of great significance for the development and theoretical research of new microemulsions.

Focused on developing a biocompatible and ecofriendly extraction platform, aqueous two-phase systems (ATPS) containing betaine-xylitol deep eutectic solvent (DES), three smallmolecular alcohols (1-propanol, 2-propanol, and tert-butanol), and water were investigated here. The effect of alcohol properties on the efficiency to form ATPS with aqueous solution of DES was studied at 298.15 K and atmospheric pressure. The results suggested that the formation of the ATPS was attributed to the incompatibility between the DES and alcohol in aqueous medium, allowing the increase in the biphasic region using tert-butanol with the highest hydrophobicity among three alcohols. Combined with Karl Fischer titration, the high-performance liquid chromatography (HPLC) analysis was used to evaluate the tie-lines of the ATPS, and it was found that DES components were enriched in the lower phase while alcohol was transferred preferentially to the upper phase. Additionally, the increase in the concentrations of ATPS phase compositions was responsible for the increase in the length of tie-lines, which led to a higher driven force for phase separation. The detailed experimental data were highly correlated by the NRTL model based on a low root-mean-square deviation (≤1.79%). Moreover, five biomolecules (gallic acid, syringic acid, quercetin, kaempferol, and isorhamnetin) were used as probes to determine the extraction ability of the studied DES/alcohol ATPS. This work may lay a promising foundation for the diversity development of the ATPS.

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