A Search for Natural Hydrophobic Deep Eutectic Solvents Based on Natural Components

Abstract

Deep eutectic solvents (DESs) based on terpenes are identified and characterized. 507 combinations of solid components are tested, which results in the identification of 17 new hydrophobic DESs. Four criteria are introduced to assess the sustainability of these hydrophobic DESs from a chemical engineering point of view. These criteria include a viscosity smaller than 100 mPa•s, a density difference between DES and water of at least 50 kg•m −3 upon mixing of the DES and water, low transfer of the DES to the water phase and minor to no pH change. The results show that five new hydrophobic DESs based on natural components satisfy these criteria; thymol and coumarin (2:1), thymol and menthol (1:1), thymol and coumarin (1:1), thymol and menthol (1:2) and 1-tetradecanol and menthol (1:2), and thus are promising DESs. These new DESs can be considered as natural deep eutectic solvents, which have the potential to be environmentally friendly. A selected group of the hydrophobic DESs were used for the extraction of riboflavin from water. They all show higher removal of riboflavin in comparison to decanoic acid:tetraoctylammonium bromide (2:1). The highest extraction efficiency of riboflavin from water, 81.1%, was achieved with the hydrophobic DES DecA:Lid (2:1).

Greener Terpene–Terpene Eutectic Mixtures as Hydrophobic Solvents

“…This is related to evaporation or sublimation of the compounds and not to their degradation as previously stated. 37 Pure components and their mixtures show similar mass loss patterns with a single-step decay with the exception of C + S and B + S that present a second plateau. This is attributed to interactions between the pure components that cause different evaporation temperatures.…”

Phenolic hydrogen bond donors in the formation of non-ionic deep eutectic solvents: the quest for type V DES

“…Besides, it prevents the identification of patterns and specific interactions that may originate new DES. For instance, van Osch et al 15 work whether the melting temperature depression observed in the studied systems is due to specific, strong interactions between their components or simply due to their melting properties, as in the case of the thymol systems investigated by Martins et al 11 By measuring the solid-liquid equilibrium phase diagram of the system thymol/(À)-menthol (henceforth referred to as menthol), reported in Fig. 1 and Table S1 (ESI †), a new true deep eutectic solvent was here identified.…”

“…Moreover, recently some authors proposed that a mixture with a 1 : 2 mole ratio of thymol : menthol was a DES. 15 However, since the phase behaviour of the mixture was not investigated, the unique behaviour of the system was not recognised, nor the nature or stoichiometry of its interactions.…”

Oil-in-water emulsions based on hydrophobic eutectic systems

“…The system we investigate is based on a dispersed hydrophobic eutectic mixture in water. These ES-in-H 2 O emulsions comprise a hydrophobic ES of 1-tetradecanol (1-tdc) and menthol (Men), 21 which has a liquid window at room temperature, with sodium dodecyl sulphate (SDS) as surfactant. The effects of surfactant concentration, mass fraction of oil (ES) droplets, the addition of salt and sonication time on the droplet size evolution are studied.…”

“…Parameters for the LSW theory for decane25 and 1-tdc : Men (1 : 2) 21. The interfacial tension is of the oil-water interface, where the water phase contains SDS at bulk concentrations above the CMC…”