Selection of the most environmentally benign ionic liquids option by coupling OECD standardized tests and fish leucocyte mortality
Résumé
To reduce health and environmental risks of chemicals and to minimize the environmental footprint of human activities, green chemistry searches for alternative, environment-friendly reaction media and at the same time strives to increase reaction rates and milder reaction conditions. A growing area of research is devoted to ionic liquids (ILs) often termed as “designer” solvents due to the extreme tunability of sought functional properties. As the aftermath of earlier misleading messages reporting ILs generically as intrinsically “safe and risk free” whatever ILs considered, their increase in potential or emerging applications in key domains (like bio-refining, energy storage, nano-material processing, pollution remediation…) dictates a more scientifically-sound approach of actual risk profiles of ILs, including both physico-chemical, health and environmental risks that might be triggered by inadequate selection of use of ionic liquids. In this context, we proposed a advanced approach serving comprehensive evaluation of environmental hazard by combined use of OECD standardized tests (Daphnia magna acute immobilization test ; algal growth inhibition test) and fish ex vivo leucocyte mortality analysis. This innovative approach integrating multicriteria assessment has been tested to on a first set of seven imidazolium-based ([BMIM][Cl], [EMIM][Cl], [EMIM][DCA], [EMIM][MeSO3], [EMIM][EtOSO3], [EMIM][BF4], [HMIM][Cl]) and four phosphonium-based ionic liquids ([P6,6,6,14][Cl], [P6,6,6,14][DCA], [P6,6,6,14][(iC8)2PO2], [Pi4,i4,i4,1][TOS]) and is expected to be further used to examine other ILs (biobased, ILs, pyrrolidinium, …) in soon future. Results of ecotoxicity tests obtained so far have revealed a clear potential to rank clearly the families of ILs according to the studied risk and even to identify influencing structural factors within a same family of ILs and compounds within the same family. Complementarity of these tests and ecotoxic properties of IL will be discussed specifically in terms of ecological footprint reduction strategies in chemical engineering processes for successful IL utilization in the future.