Ionic liquids as lubricants or lubrication additives: An ecotoxicity and biodegradability assessment

This paper reports on the (eco)toxicity and biodegradability of ionic liquids considered for application as lubricants or lubrication additives. Ammonium- and pyrrolidinium-based cations combined with methylsulphate, methylsulphonate and/or (CF3SO2)2N− anions were investigated in tests to determine their aquatic toxicity using water fleas Daphnia magna, green algae Selenastrum capricornutum and marine bacteria (Vibrio fischeri). Additional test systems with an isolated enzyme (acetylcholinesterase) and isolated leukaemia cells from rats (IPC-81) were used to assess the biological activity of the ionic liquids. These compounds generally exhibit low acute toxicity and biological activity. Their biodegradability was screened according to OECD test procedures 301 B and 301 F. For choline and methoxy-choline ionic liquids ready biodegradability was observed within 5 or 10 d, respectively. Some of the compounds selected have a considerable potential to contribute to the development of more sustainable products and processes.

► The investigated ILs predominantly show no or just minor toxic effects.
► For some ILs excellent biodegradation rates of >80% were obtained within 15 d.
► A prospective design of environmentally favourable ILs seems feasible.