Utilization of Ionic Liquids for the Separation of Organic Liquids from Industrial Effluents

Abstract

The recovery of aromatic organic solvents from mixtures containing aliphatic compounds has economic as well as environmental significance. This is so because viable methods have not been established for the recovery from mixtures in which the components of value are 20 % (v/v) or less. In the light of this, we investigated the efficacy of selected ionic liquids to recover aromatic solvents from prepared mixtures. We used 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO₄] and 1-ethyl-3-methylpyridinium ethyl sulfate [EMpy][EtSO₄] to separate and recover aromatic hydrocarbons (less than 10 % (v/v)) from aromatic/aliphatic hydrocarbon mixtures, namely, benzene, toluene, ethyl benzene and o-xylene (BTEX) from n-heptane at 40 °C. The same aromatic components were used with n-hexane as an alkane and 1-ethyl-3-methylpyridinium ethyl sulfate [EMpy][EtSO₄] as an ionic liquid. The concentrations of the aromatic components used were in the range of 2.5–10 % (v/v) for the following multi-systems at 40 °C:
• Benzene + toluene + ethyl benzene + o-xylene + n-heptane + [EMIM][EtSO₄].
• Benzene + toluene + ethyl benzene + o-xylene + n-hexane + [EMIM][EtSO₄].
• Benzene + toluene + ethyl benzene + o-xylene + n-hexane + [EMpy][EtSO₄].
The % removal of each aromatic, the ionic liquid selectivity trend, as well as its lifetime, and the distribution pattern of aromatic components in the ionic liquid obtained by gas chromatography were used to determine the capability of [EMIM][EtSO₄] and [EMpy][EtSO₄] as extracting solvents for low concentration BTEX.

Keywords: Ionic liquids, solvent extraction, BTEX, aromatic hydrocarbons, aliphatic hydrocarbons