Combining Phytoremediation and Biorefinery Strategies Assisted by an Ecofriendly Zwitterionic Ionic Liquid: A New Challenge for a Cleaner Bioeconomy

This study aims to investigate the ability of an imidazolium biobased Zwitterionic Ionic Liquids (ZILs) in enhancing the phytoextraction of copper from garden and vineyard soils using the model plant ryegrass (Lolium perenne L.). The copper/ZIL molar ratio (1/4) introduced was rationally established based on molecular modeling and on the maximal copper concentration in artificially contaminated soil. Higher accumulation of copper in the shoots was detected for the uncontaminated and copper contaminated ZIL amended soils (18.9 and 23.3 mg.kg-1, respectively) together with a similar ZIL concentration of around 3% w/w detected by LC-MS analyses. These data evidenced a phytoextraction improvement of 38 and 66% compared to non-amended soils. ZIL would be mainly present under Cu(II)-ZIL4 complexes in the shoots. However depending on the soil modalities, the presence of free copper and/or free ZIL led to different chemical compositions in lignin and monomeric sugar contents. In the biorefinery context, performances of enzymatic hydrolysis of shoots were related to the presence of both ZIL and copper under free or complex forms. Ecotoxicity of the different soils indicated that the quantity of copper and ZIL remaining in the soils had no significant toxicity. ZIL amendment in a copper-contaminated soil was demonstrated as being a promising way to promote the valorization of phytoremediation plants.