A comparative study between ionic liquid coating and counterparts in bulk for toluene absorption

The structure-activity relationship (SAR) for toluene absorption and desorption in ionic liquids (ILs) has been investigated for seven commercial ILs in bulk and thin liquid layer. ILs with imidazolium cations of different alkyl chain lengths and a Hofmeister series of anions including [CH3COO], [I], [BF4], [HSO4], and [PF6] were included. Absorption capacity for toluene increases with increasing kosmotropicity of the cation and anion, while the absorption rate in bulk ILs is governed by viscosity and that in thin ILs layer by the oil-water partition coefficient (Kow). A regenerability coefficient (Rp) measures toluene desorption and IL regeneration. The release rate as measured by dRp/dt correlates well with the Kow and viscosity of the ILs and tx, the time required to completely desorb toluene is related to its ionic strength as measured from v(C2H) of the imidazolium cation. These properties are in turn governed by the kosmotropicity of the cation and anion pair forming the IL