Environmental Implications of Ionic Liquid and Deep Eutectic Solvent in Geothermal Application: Comparing Traditional...

Area of Science:

• Environmental toxicology
• Green chemistry
• Ecotoxicology

Background:

• Ionic liquids (ILs) and deep eutectic solvents (DES) are increasingly researched for applications like enhanced geothermal systems (EGS).
• Previous assumptions of ILs and DES being environmentally benign due to low vapor pressure are being challenged by emerging toxicity data.
• Ecotoxicity studies are crucial to understand the environmental impact of these novel compounds.

Purpose of the Study:

• To evaluate the acute and chronic toxicity of hexylepyradinium bromide (HPyBr) and choline chloride with magnesium chloride hexahydrate (ChCl:MgCl2·6H2O).
• To assess the toxicity across multiple species, including algae, water fleas, fathead minnows, and earthworms.
• To compare traditional toxicity testing with new approach methods (NAMs) using fish embryos and cell lines.

Main Methods:

• Standardized ecotoxicity assays were performed on five test species: *Raphidocelis subcapitata*, *Ceriodaphnia dubia*, *Daphnia magna*, *Pimephales promelas*, and *Eisenia fetida*.
• New approach methods (NAMs) were employed, including the fathead minnow embryo test and the RTgill-W1 assay using rainbow trout gill cells.
• Acute and chronic toxicity endpoints were measured to determine dose-response relationships.

Main Results:

• Choline chloride with magnesium chloride hexahydrate (ChCl:MgCl2·6H2O) exhibited lower toxicity compared to hexylepyradinium bromide (HPyBr).
• Hexylepyradinium bromide (HPyBr) demonstrated significant toxicity across multiple test species.
• Comparative analysis revealed potential risks of ChCl:MgCl2·6H2O to aquatic life, emphasizing cumulative environmental effects.

Conclusions:

• Hexylepyradinium bromide (HPyBr) requires careful handling due to its high toxicity.
• Choline chloride with magnesium chloride hexahydrate (ChCl:MgCl2·6H2O), while less toxic than HPyBr, still presents environmental concerns for aquatic ecosystems.
• Further research and risk assessment are necessary for the safe application of ILs and DES in industrial processes.