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Most of the works carried out on deep eutectic solvents (DESs) make reference to their physicochemical properties, and the analysis of their toxicological behavior on the environment and biodegradability are still limited. In this work, an exhaustive study on the ecotoxicity of three pure deep eutectic solvents (reline, glyceline, and ethaline) and their mixtures with water (reline-water, glyceline-water, and ethaline-water) was carried out in different biomodels: bacteria (A. fisheri), crustaceans (D. magna), and algae (S. capricornatum). In addition, the amount of chlorophyll in the algae after exposure to the DESs was analyzed. Finally, the biodegradability of the studied DESs was also analyzed. The ecotoxic behavior strongly depends on both the biomodel tested and the presence of water in the mixture, resulting in low toxicities in all cases. Furthermore, most of the deep eutectic solvents studied can be considered readily biodegradable. A comparison of the ecotoxicity and biodegradability of these solvents under other conditions has also been provided, and a complete analysis is given.

Deep eutectic solvents (DESs) have high viscosities, but known to be mitigated by addition of suitable co-solvent. The effect of such co-solvent on the extraction efficiency of the hybrid solvent is hardly known. This study examined the effect of ethanol on three choline chloride-based DESs (glyceline, reline, and ethaline) by mixing each in turn with ethanol in various volume proportions. The hybrid solvents were evaluated for the extraction of benzene from n -hexane. Pseudo-ternary liquid-liquid equilibrium data were obtained using the refractive index method at 303 K and 1 atm for the systems, n -hexane (1) + benzene (2) + hybrid solvent (glyceline/ethanol, ethaline/ethanol, reline/ethanol) (3), and used to evaluate distribution coefficient ( D ) and selectivity ( S ). Furthermore, the physicochemical properties of the hybrid solvents were also determined. The results indicate increase in selectivity with increasing ethanol addition up to 50% and decrease with further addition. All hybrid solvents with 50% ethanol outperform sulfolane and are suitable replacement for same as green and sustainable extractant for aromatics from aliphatics. The glyceline + 50% ethanol emerged the overall best with 49.73% elevation in selectivity and 41.15% reduction in viscosity relative to the neat glyceline. The finding of this study is expected to fillip the drive for paradigm shift in petrochemical industries., Supplementary Information: The online version contains supplementary material available at 10.1007/s13203-021-00282-y., (© The Author(s) 2021.)