Ecotoxicity risk assessment of amines used in 'switchable water' and CO₂-capturing processes

Utilizing amines and alkanolamines as CO₂-capturing agents and water-soluble ionogens in 'switchable water' systems is an intensively explored research area. However, the potential risks of such amine derivatives to the environment have been poorly evaluated. In this work, we report on the ecotoxicological effect of relevant amines and alkanolamines in an aqueous environment on various classes of organisms such as bacteria (Aliivibrio fischeri), vascular plants (Spirodela polyrhiza), and invertebrates (Daphnia magna). The measured half maximal effective concentration (EC₅₀) data indicate that all tested alkanolamines and most amines have EC₅₀ values over 100 mg L^-1 and can be classified as practically harmless or harmless. On the other hand, tetramethyl-1,3-propane diamine afforded EC₅₀ values between 61 and 73 mg L^-1, indicating moderate toxicity towards invertebrates and vascular plants. Moreover, we observed a good agreement between the experimental results and the ECOSAR predictive model. Thus, our work indicates that hydrophilic amines and alkanolamines utilized in emerging CO₂-mediated processes can generally be considered harmless or practically harmless in an aqueous environment towards bacteria, vascular plants, and invertebrates, except more lipophilic diamines, which may need careful consideration.