It is known that some neat room-temperature hydrophobic ionic liquids can extract metallic species from aqueous solutions. The unique properties of such organic media allow for the application of polymerization techniques to convert the liquid organic phase to a solid one. In this work, a pyrrolidinium-based ionic liquid and a corresponding polymer with a bis(trifluoromethanesulfonyl)imide counter anion have been considered for optimization of thallium(III) migration in liquid–liquid and solid–liquid extraction systems. Neither trivalent indium nor monovalent thallium was absorbed by the polymer layer. A mathematical model to describe the mechanism of metal extraction in these systems has been developed. Thermodynamic parameters such as adsorption enthalpy, entropy, and Gibbs energy have also been determined.