Gold “Self-Leaching” in Chloride-Rich Media

Gold leaching is a fundamental process in extractive metallurgy, which is traditionally carried out using cyanide, posing environmental concerns and facing increasingly strict regulations. In the quest for cyanide-free alternatives, the present work introduces a new gold leaching reaction in chloride-rich media, whereby Au(III) is used as the oxidizing agent for the dissolution of gold as a Au(I)-chloro complex. It is demonstrated that this “self-leaching” comproportionation reaction is efficient in a broad range of aqueous, nonaqueous, deep eutectic, and ionic liquid solvents. The influence of parameters, such as acidity and viscosity, on the occurrence of the self-leaching reaction is assessed by voltammetric and chronopotentiometric experiments. It is shown that the dissolution of gold is driven by nonequilibrium conditions sustained by mass transport. This mechanism enables efficient gold recovery with excellent atom economy and low E-factors, highlighting its potential as a sustainable alternative to cyanide-based methods.