Electrochemical Characterization of Silver and Iron Ions in Choline Chloride-Ethylene Glycol DES Electrolyte

Solar energy is growing to be an important source of renewable energy in the world, and the need of recycling processes to recover the strategic materials used for this technology are necessary. Ag may be recovered from photovoltaic cells using a Deep Eutectic Solvent (DES), by selectively dissolving Ag from the waste to Ag(I) by use of an Fe(III)/Fe(II) redox couple before the recovery of Ag metal by electrowinning. Electrochemical characterization of Ag and Fe ions in ethaline DES showed that Ag, Ag(I), Fe(II) and Fe(III) ions are stable, and the standard potentials of the relevant reactions are sufficiently far from one another for the electrochemical recovery of Ag. Diffusion coefficient were estimated to be 1.77-4.16 ·10 -7 cm 2 /s and 2.02-3.19 ·10 -7 cm 2 /s for Ag(I) and Fe(II) ions, respectively. High quality Ag deposits were obtained with Fe ions in the solution, and with water content up to 10 wt% in the DES electrolyte.