Selective Electrorefining of Silver from Eutectic Mixtures Containing Silver and Copper at Solar-Panel Waste Ratio

Recycling of photovoltaic (PV) cells is a challenge for recovery of silver and copper, located in the core layer of panels. However, recovery of pure silver continues to be difficult due to parasitic reactions involving co-deposition of copper and silver. This work investigates the electrochemical behavior of Choline-chloride based eutectic mixtures (Ethaline, Propeline, Oxaline, and Reline) in order to achieve selective silver recovery in reproducible conditions. This is possible due to a stable hydration level of 5% achieved at 50 °C, where the physico-chemical and electrochemical properties were found to be stable. The nature of silver or copper complexes in eutectic mixtures was then studied to understand the electrochemical behavior of metal complexes. High-purity silver electrodeposits were obtained in two different Ag: Cu ratios of 1: 1 and 1:17, respectively, the latter mimicking the ratio obtained in PV waste leaching solutions. High silver recovery rate were obtained independently on the eutectic mixture. In the lower Ag: Cu ratio (1:17), purity of the silver deposit depends on the nature of the copper complexes and on electrolyte viscosity. In Reline, a copper-free silver deposit was obtained with a high recovery rate reaching 94.6%.