Liquid-liquid extraction of phenolic compounds from water using ionic liquids: Literature review and new experimental data using [C2mim]FSI

Abstract

In this work, the capability of the ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, [C₂mim]FSI, to extract o-cresol, 2-chlorophenol, resorcinol and phenol from water, reaching the legal limit of 1 mg L^-1 was analyzed. The extraction process was carried out for each one of these phenolic compounds varying the initial concentration in water from 3 mg L^-1 to 1000 mg L^-1, and for aqueous mixtures of the four phenolic compounds in the same concentration range. Because of the scarcity of physical properties of the [C₂mim]FSI, density, speed of sound, dynamic viscosity and refractive index were measured from 293.15 to 343.15 K at atmospheric pressure. From the experimental data, the thermal expansion coefficient and the isentropic compressibility for the pure ionic liquid were calculated. Even though [C₂mim]FSI is hydrophobic, it can solve small quantities of water that can hinder the recovery of the ionic liquid, consequently the solubility of water in the ionic liquid was determined at several temperatures and atmospheric pressure. In addition to experimental data, a literature review on the use of ionic liquids to extract phenolic compounds from water was performed.

Keywords: 2-Chlorophenol; FSI; Ionic liquids; Phenol; Resorcinol; o-cresol.