Porous ionic liquids from cyclodextrin carbon for deep extraction of polycyclic aromatic hydrocarbons

Abstract

In extraction processes, the low mass transfer efficiency of conventional ionic liquids is a refractory problem. Herein, a porous ionic liquid (PIL), β-CD-900-PIL, was innovatively constructed by combining a porous carbon material (β-CD-900) derived from β-cyclodextrin polymer with imidazole bis-trifluoromethylsulfonylimide ionic liquid ([C₁₂mim][NTf₂]). The N₂ sorption isotherm and CO₂ adsorption confirmed the porosity of β-CD-900 and the PIL. With the dispersion amount of β-CD-900 as 20 wt%, the extraction efficiency of naphthalene by β-CD-900-PIL reached 66.6%, which was 24% higher than that of the ionic liquid. After three extractions, the naphthalene content decreased from 500 mg L⁻¹ to 5 mg L⁻¹. The high extraction efficiency was attributed to the high porosity and abundant π–π and C–H⋯π interactions between PILs and naphthalene. The more than 99% extraction performance, low viscosity and low preparation cost make β-CD-900-PIL an ideal extractant for polycyclic aromatic hydrocarbons in the petrochemical industry.