Inventory of biodegradation data of ionic liquids

Area of Science:

• Green Chemistry
• Environmental Science
• Chemical Engineering

Background:

• Ionic liquids (ILs) are gaining traction for environmentally open applications.
• Complete mineralization of ILs is highly desirable for environmental safety.
• Assessing the biodegradability of ILs is critical for their sustainable use.

Purpose of the Study:

• To review the current knowledge on the environmental biodegradability of ILs.
• To identify research gaps and needs in IL biodegradability testing.
• To evaluate the validity and reliability of existing IL biodegradation data.

Main Methods:

• A comprehensive literature review of 109 studies on IL biodegradation.
• Evaluation of studies based on standard testing methods (e.g., OECD, ISO, APHA).
• Classification of ILs by cation core structure and biodegradation data using a traffic light system (red, amber, green).

Main Results:

• Significant limitations in the reliability and quality of existing IL biodegradation data were identified due to missing parameters and non-compliance with test guidelines.
• Cholinium-based ILs demonstrated the highest biodegradability (≥ 60%).
• Phosphonium and imidazolium-based ILs exhibited lower biodegradability, with phosphonium ILs being the least biodegradable.

Conclusions:

• There is a critical need for more rigorous and qualitatively superior testing of IL biodegradability using standardized methods.
• Consistent reporting of all validation criteria is essential for reliable data comparison and understanding IL environmental impact.
• Improved data will facilitate the selection of environmentally benign ILs, especially when environmental release is unavoidable.