Ionic liquids in soils: effects of different anion species of imidazolium based ionic liquids on wheat (Triticum aestivum) as affected by different clay minerals and clay concentrations

This study contributes to a prospective hazard assessment of ionic liquids, focusing on the terrestrial environment. The influence of differently composed soils—varying contents of the clay minerals smectite and kaolinite—on the toxicity of different anion species of imidazolium based ionic liquids was studied for growth inhibition of wheat (Triticum aestivum). IM14 (CF₃SO₂)₂N appeared the most toxic, independently of the investigated soil type. The toxicity of IM14 Cl, IM14 BF₄ and IM14 HSO₄ was mainly dominated by the cationic moiety. The observed effects varied in dependence of the added clay type and clay concentration. An increase of clay content resulted in less pronounced effects of these substances. In contrast, for IM14 (CF₃SO₂)₂N the addition of clay minerals caused higher toxic effects in comparison to the reference soil. Our results give first hints for the assumption, that ionic liquids whose toxic action is based on the anionic moiety are especially hazardous for soils, particular for soils with high clay contents.