Biodegradability and Ecotoxicity Profiles of Choline Acetate, Betaine, and L-Proline NADESs: A Hidden Threat for Eutrophication?

Deep Eutectic Solvents (DESs) and in essence naturally available DESs (NADESs) are considered to be green solvents due to their low vapor pressure, non-flammability, thermal stability, good solvent power and low oxicity. These properties make them attractive as safer and more environmentally acceptable solvent options. Green Chemistry promotes the use of renewable and biocompatible compounds such as amino acids, lipids and acids of natural origin to yield more sustainable DESs, which yields their application in several industrial processes. Driven by the current requisite for sustainable progress, along with overcoming dependence on fossil-based resources, the current work details important findings pertaining to the design of sustainable NADESs from the perspective of green chemistry to exhibit suitable physico-chemical properties and a low toxicological profile. Biodegradation studies using OECD 301D closed bottle test (CBT) were performed to observe the biodegradability of 15 selected NADESs. Toxicity controls were run along with the CBT run to observe the behavior of these NADESs in the environment. In this framework, the present paper investigates the development of safer NADESs. The results obtained suggest that our synthesized NADESs, have high biodegradability and low toxicity towards microalgae. Although a conventional threat to the environment would seem out of reach, it must be hypothesized that such compounds might act as enhancers of eutrophication phenomena.