Leaching foams: toward a more environmentally friendly process for the recovery of critical metals from electronic wastes

The recovery of metals from WEEE, Waste from Electrical and Electronic Equipment, is a major challenge to preserve natural resources. Hydrometallurgy, which consists in leaching metals is a promising method but generates large amounts of effluents which need to be collected and concentrated. In this study we design aqueous leaching foams, composed of 90% v/v of gas and 10% v/v of HCl solution to oxidize and dissolve copper. We take advantage of the oxidizing power of the dioxygen (O2) present in the air bubbles whose fast transfer through the 2 foams enables an efficient oxidation of copper. We then extend the concept of leaching foams to another gas, ozone, to oxidize silver (Ag). We finally show that using an anionic surfactant to complex cupric ions helps improving the dissolution of the metal. These promising results open new recycling routes for metals contained in WEEE, with a lower environmental footprint.