Eco-Friendly and Super-Rapid Dissolution of Silver without Acid and Cyanide via a Self-Catalytic Oxidation and Ylide-Coordination Process

Typically, the dissolution of monomeric silver (Ag) is achieved through the use of cyanide and/or strong acid/strong oxidant reagents. The development of eco-friendly and efficient solvents is of significant importance to achieve the smelting and recycling of Ag in a sustainable mode. Herein, we demonstrated that an eco-friendly solvent could realize a super-rapid and efficient dissolution of Ag. With the assistance of H2O2, a 1-allyl-3-methylimidazolium chloride (AmimCl) ionic liquid dissolved Ag powder rapidly, and the Ag concentration reached 8.3 wt %. Notably, this dissolution process eliminates the need for acids, cyanides, or harsh conditions, with water being the sole byproduct. Subsequently, after the precipitation and separation of Ag, AmimCl could be effectively recycled and reused by removing water. The whole process had no emission of wastes. The mechanism showed that Ag catalyzed H2O2 to produce a high concentration of oxygen, promoting the oxidation of Ag powder. Then, the cation [Amim]+ and anion Cl– in AmimCl interacted with Ag2O to form [Ag(Amim-ylide)2]+ and [AgCl2]− ions, achieving the dissolution of the Ag powder. Furthermore, due to the protective effect of ionic liquids on metal nanoparticles, uniform Ag nanoparticles (Ag NPs) with a diameter of 10 nm were fabricated in situ, and they demonstrated ultrahigh stability after one year. They were used to prepare a cellulose/Ag NP nanocomposite film with excellent antimicrobial properties. Therefore, a fast and eco-friendly dissolution of Ag was realized via a self-catalytic oxidation and ylide-coordination effect, indicating a revolutionary strategy for the sustainable smelting, using, and recycling of silver ores and other silver-containing substances.