Recovery of metallic gold, silver and copper from end‑of‑life mobile phones by hydrometallurgy

The global amount of end-of-life mobile phones is increasing over the years and their proper valorization is nowadays of strategic importance. Mobile phones can be considered as an important source of valuable materials, such as metals, plastics, and glass, which can be recovered and reintroduced into new production cycles. In this paper, a recovery process based on selective materials’ separation and hydrometallurgy was proposed. After manual dismantling followed by the separation of the different fractions (plastic, metallic fraction, printed circuit boards, batteries, displays and glass), a hydrometallurgical process based on leaching and precipitation/reduction was applied on printed circuit boards with the aim of recovering the metals of interests. Tin was precipitated from an aqua regia leachate with gaseous ammonia and gold was afterward recovered as metallic gold by reduction with sodium borohydride; silver was first precipitated as silver chloride from a nitric acid leachate and then reduced to metallic silver. Copper was selectively precipitated with oxalic acid from the solution coming from silver recovery and then recovered as metallic copper by means of a mild thermal treatment, without chemicals addition. The developed process allowed the recovery of gold, silver and copper in metallic form with yield and purity grade ≥ 98%.