abstract
Most ionic liquids (ILs) are either water soluble or present a non-negligible miscibility with water that
may cause some harmful effects upon their release into the environment. Among other methods, adsorption
of ILs onto activated carbon (AC) has shown to be an effective technique to remove these compounds
from aqueous solutions. However, this method has proved to be viable only for hydrophobic ILs rather
than for the hydrophilic that, being water soluble, have a larger tendency for contamination. In this context,
an alternative approach using the salting-out ability of inorganic salts is here proposed to enhance
the adsorption of hydrophilic ILs onto activated carbon. The effect of the concentrations of Na2SO4 on the
adsorption of five ILs onto AC was investigated. A wide range of ILs that allow the inspection of the IL cation
family (imidazolium- and pyridinium-based) and the anion nature (accounting for its hydrophilicity
and fluorination) through the adsorption onto AC was studied. In general, it is shown that the use of
Na2SO4 enhances the adsorption of ILs onto AC. In particular, this effect is highly relevant when dealing
with hydrophilic ILs that are those that are actually poorly removed by AC. Furthermore, the COnductor
like Screening MOdel for Real Solvents (COSMO-RS) was used aiming at complementing the experimental
data obtained. This work contributes with the development of novel methods to remove ILs from water
streams aiming at creating ‘‘greener’’ processes.