Adsorption of alkylimidazolium and alkylpyridinium ionic liquids onto natural soils.

The mechanism of ionic liquid sorption onto selected natural soils differing in their organic content, cation exchange capacity, and particle size distribution was investigated in detail. Isotherms were employed to describe sorption. In most cases,the maximum achievable surface concentrations were well above CEC values. This observation may indicate that initially sorbed solutes modify the sorbent, a process favoring further sorption. The experimental data suggest that if a multilayer process occurs, such a mechanism will be applicable to all ionic liquids; but saturation of the second layer occurred only with the longest alkyl chain compound. The shorter alkyl chain cations did not reach saturation in the concentration range investigated here. The influence of the varying pH and ionic strength of an aquifer on sorption strength was also determined.