(Eco)toxicity and biodegradability of protic ionic liquids.

Area of Science:

• Green Chemistry
• Environmental Toxicology
• Microbiology

Background:

• Protic ionic liquids (PILs) are often marketed as eco-friendly, but their environmental impact and toxicity require thorough investigation.
• Limited data exists on the ecotoxicity of PILs across various organisms and trophic levels.

Purpose of the Study:

• To evaluate the antimicrobial activity, aquatic toxicity, and phytotoxicity of four N-methyl-2-hydroxyethylammonium-based PILs.
• To assess the biodegradability of these PILs using biochemical oxygen demand (BOD) and chemical oxygen demand (COD) ratios.

Main Methods:

• Antimicrobial activity tested against Staphylococcus aureus, Escherichia coli, Candida albicans, and Fusarium sp.
• Aquatic toxicity assessed using the Microtox® assay with Vibrio fischeri.
• Phytotoxicity evaluated using Lactuca sativa (lettuce) seeds.
• Biodegradability determined by BOD/COD ratio.

Main Results:

• Increasing alkyl chain length in PILs generally enhanced toxicity towards tested microorganisms, aquatic bacteria, and plants.
• N-methyl-2-hydroxyethylammonium acetate (m-2-HEAA) exhibited the lowest toxicity, while N-methyl-2-hydroxyethylammonium pentanoate (m-2-HEAP) showed the highest.
• All four PILs demonstrated low biodegradability, suggesting persistence in the environment.

Conclusions:

• The environmental friendliness of PILs is questionable and depends on their specific chemical structure.
• Alkyl chain length is a critical factor influencing PIL ecotoxicity and biodegradability.
• Further research is needed to fully understand the environmental fate and impact of PILs.