Exploring ionic liquids for formaldehyde separation via computational COSMO-RS screening

Abstract

Formaldehyde is an emerging human carcinogen from gaseous spark ignition engines and in aqueous stream. In addition to causing leukaemia and nasal cancer, the emissions harm the environment. The present study examined ionic liquids (ILs) as greener alternatives for removing formaldehyde from different sources. Because of its reliability and excellent predicting ability a conductor-like screening model for real solvents (COSMO-RS) were employed as a simulation means to evaluate potential ILs for formaldehyde. Screened IL can be used as an extracting agent, an adsorbent, a carrier, or an absorbent in formaldehyde separation. 392 different cation-anion combinations were screened. To measure the efficacy of IL, the activity coefficient at infinite dilution, capacity, selectivity, and interaction energies were predicted for all 1600 ILs combinations. Short-chain quaternary ammonium cations were found to be potentially effective compared to long-chain and aromatic cations. Moreover, halogenated and food-grade anions such as fluoride, acetate, and lysinate showed higher capacity and selectivity. Whereas than weakly coordinating anions such as [AsF6] and [BCl4] were observed to be least effective for formaldehyde separation. ILs tetramethylammonium hydroxide [TMAmm][OH], tetramethylammonium fluoride [TMAmm][F], tetramethylammonium acetate [TMAmm][Ac], and [TMAmm][Lys] were found to be the most effective separating agents for formaldehyde. This study will facilitate the selection and design of biobased ILs for the separation of formaldehyde.