Electrochemical Long‐Term Stability of a Choline Chloride‐Based Deep Eutectic Solvent for Silver Recycling

Deep eutectic solvents (DES) are investigated since 20 years as ionic liquids alternative for electrochemical applications due to their reduced toxicity and cost. Metal electrowinning, is a process which is especially attractive for DES, since it allows the replacement the polluting state‐of‐the‐art hydrometallurgical routes. Though, the solvent interest is conditioned to the DES long term stability under operating conditions. In this article experimental proofs of the long term stability of Propeline 1:3 both in storage and under electrochemical operation conditions, is provided using silver electroleaching‐ electrodeposition process as a model electrochemical system for the DES aging study. The solvent long term stability is evaluated during prolonged storage without electrochemical stress, providing a baseline for long‐term usability. The electrochemical stability window of Propeline 1:3 is then determined, and its electrochemical degradation is forced for days in order 1) to identify degradation products and 2) to understand degradation mechanism that DES can encounter during extreme operating conditions. Finally, Propeline 1:3 long‐term stability under operation conditions is evaluated using different electroleaching‐electrodeposition current densities by the monitoring of degradation product formation. The impact of DES aging on the performances of silver electrowinning is assessed through a comparative analysis of fresh and aged electrolyte.