Separation of gold(III) in acidic chloride solution using porous polymeric ionic liquid gel

A novel polymeric ionic liquid (PIL) gel was synthesized via radical polymerization of the ionic liquid monomers, 1-vinyl- 3-ethylimidazoliumbis(trifluorometyl-sulfonyl) imide ([veim][Tf2N]). The gel was made porous by removing the water phase dispersed by polyoxyethylene (20) sorbitan monolaurate (Tween-20). The porous structure of the synthesized gel was observed by SEM imaging. In comparison to the nonporous PIL gel synthesized without Tween-20, the adsorption capacity of Au(III) onto porous PIL gel was enhanced. The adsorption behavior of the synthesized gel was studied in acidic chloride solutions containing various metal ions, and it was found that the gel selectively adsorbed Au(III) over other metal ions. Maximum adsorption capacity of Au(III) was more than 140 mg/g; whereas, those for Pt(IV) and Pd(II) were lower than 20 mg/g. The adsorbed Au(III) onto the gel can easily be desorbed using an acidified thiourea aqueous solution. The feasibility of utilizing the polymeric ionic liquid gel for the separation of Au(III) was thereby demonstrated.