Further studies on the biodegradation of ionic liquids

A range of ionic liquids (ILs) containing a pyridinium cation were synthesised and their biodegradability was evaluated using the CO2 headspace test (ISO 14593). ILs bearing a 1-(2-hydroxyethyl) side chain were prepared from either pyridine or nicotinic acid derivatives. These ILs showed high levels of biodegradation under aerobic conditions and can be classified as 'readily biodegradable'. In contrast, pyridinium ILs with methyl or ethyl ether side chains showed significantly lower levels of biodegradability in the same test. Biodegradation studies on a range of novel ILs with acetal and carbamate functionalities, as well as thiazolium-based salts, also showed low levels of mineralization.