“Egg of Columbus”: Single-step complete removal of chloride impurities from ionic liquids by AgCl deposition on silver electrode

•Simple, effective, safe one-step process for Cl− complete removal in ionic liquids•Quantitative Cl− capture by electrodeposition on Ag wire forming Ag|AgCl electrode•Room temperature, low potentials, high current efficiency, negligible side products

Chloride impurities in ionic liquids (ILs), which can be present even in huge amounts depending on the IL synthetic route, are particularly critical for electrochemical processes; thus, their abatement is often mandatory. However, while their analytical quantification has been the subject of many studies involving a variety of techniques, the so far available processes for their abatement are still unsatisfactory, having low efficiency, and/or involving multiple steps, and/or being far from mild and easily scalable. In this context, like an “egg of Columbus”, a quite simple and safe process for chloride abatement in ILs is proposed, practically coinciding with the electrolytic preparation of a Ag|AgCl electrode. It proceeds in a single step, at room temperature, at very low potentials, with nearly ideal current efficiencies, and with negligible side effects on the electrolyzed IL. The chloride impurities are quantitatively captured and accumulated on the silver wire and eliminated by simply removing the resulting Ag|AgCl electrode from the solution, with no need of subsequent treatments.

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