Guillaume SIMON1, Agílio PÁDUA2, Margarida COSTA GOMES2
1PULSALYS, Campus LyonTech , France
2Laboratoire de Chimie de l’ENS Lyon, France
Fluorinated substances are widely used for technical purposes in textile finishing [1], giving water or oil repellence to the fibres. Polymers with non-fluorinated backbones and perfluorinated side-chains and fluoropolyethers are the most commonly used textile additives for this purpose. During their production, textile manufacturing or consumer-use, these additives can be degraded into their precursors, mainly long-chain perfluorinated acids (e.g. perfluorooctanoic acid) or fluorotelomers (e.g. 8:2 fluorotelomer alcohol), and released in the environment. These substances are volatile, bio accumulative and persistent, and their release in the environment is more and more regulated in the EU [2].
Besides the growing interest for the use of non-fluorinated compounds, perfluorinated organic compounds with 4-6 carbon chains are generally used and are gradually substituting C8 derivatives. For a textile recycling purpose, it is necessary to find ways to safely remove them from the fibres. Among other alternative solvents, ionic liquids showed solvation properties that are promising for recycling textile waste [3]. We have used the COSMO-SAC modelling approach to screen a large number of ionic liquids and, by the calculation of infinite dilution activity coefficients [4], find the most appropriate solvents for the perfluorinated compounds. A previous study involving dyes used in textiles showed accurate estimations for imidazolium-based ionic liquids and solutes with localized charge densities [5].
We could determine which ionic liquids were able to interact favourably with perfluorobutyric acid (PFBA) and 6:2 fluorotelomer alcohol (6:2 FTOH). These information could be quantified using isothermal titration calorimetry (ITC) [6] for PFBA in 1-butyl-3-metylimidazolium bis(trifluoromethylsulfonyl)imide, [C4C1Im][NTf2], predicted by COSMO-SAC as a weak solvent, as well as in 1-ethyl-3-methylimidazolium methylsulfonate, [C2C1Im][MeSO3] and 1-butyl-3-methylimidazolium acetate, [C4C1Im][OAc], expected to have strong interactions with the textile additive. Mixing enthalpies of 6:2 FTOH were measured in selected ionic liquids, namely triethylammonium methylsulfonate, [N222H][MeSO3], 1-ethyl-3-methylimidazolium methylsulfonate, [C2C1Im][MeSO3] and acetate, [C2C1Im][OAc].
In this study, we show that computation screening using state-of-the-art semi-theoretical models available free of charge allows the prediction of major trends for the solvation properties of textile additives in ionic liquid-based solvents.
References
[1] Schellenberger S. et al., Chemosphere, 193, 675-684 (2018) ; [2] Whiting R. et al., European Commission Report (2020) ; [3] De Silva, R. et al., RSC Adv., 4 (55), 29094-29098 (2014) ; [4] Wang, S. et al., Ind. Eng. Chem. Res., 46 (22), 7275-7288 (2007) ; [5] Simon et al., manuscript in preparation ; [6] Lepre, L. F. et al., Phys. Chem. Chem. Phys., 18 (33), 23285-23295 (2016)