Efficient Solvent Extraction of Phenol Using Imidazolium-Based Ionic Liquids

Since their initial discovery, Ionic Liquids (ILs) have garnered interest from both the industrial and academic communities due to their numerous potential applications, owing to their distinctive properties. The number of existing Ionic Liquids is very significant and could be infinite, given the wide range of possibilities for combinations between cations (Ammonium, Sulfonium, Phosphonium) and anions (Organic or Inorganic). Imidazolium salts form the largest family of Ionic Liquids, it is the one that has captured our attention.

Phenolic compounds are important substances in the chemical industry and are primarily derived from coal liquefaction oil, petroleum, and biomass. However, the conventional method of phenol separation using either alkaline or acidic water leads to significant environmental issues.

In this study, a series of Imidazolium-functionalized Ionic Liquids (ILs: [EtO₂C₂mim]Br, [EtO₂C₂mim]BF₄, and [EtO₂C₂mim]PF₆) were synthesized, characterized, and their extraction abilities for phenol in a model solution of hexane and phenol were investigated using a UV-visible spectrophotometry titration method.

The results showed that Imidazolium-functionalized Ionic Liquids: [EtO₂C₂mim]Br, [EtO₂C₂mim]BF₄, and [EtO₂C₂mim]PF₆ can extract 99%, 77%, and 16% of phenol, respectively, with the best extraction performance observed with [EtO2C2mim]Br. The results indicated that the extraction efficiencies of the three ILs were significantly influenced by the nature of the anion. Overall, these ILs demonstrate high potential for phenol extraction and can be considered a powerful alternative for wastewater treatment.