One-Step Silver Leaching from Manganese-Silver Ore Enabled by Hydrogen-Bonded Network Formation.

Abstract

Silver is an increasingly scarce resource, necessitating green leaching methods for low-grade ores. Conventional cyanidation, however, suffers from extreme toxicity and environmental hazards that make it unsustainable. We report a nontoxic synergistic leaching system based on oxalic acid and cyano-functionalized branched quaternary ammonium salts. Under mild conditions, this one-step method enables efficient and selective leaching of lattice-confined silver from polymetallic manganese-silver ore, with recoveries exceeding 90%. Kinetic studies reveal a two‑stage process, with an initial rapid dissolution of exposed manganese oxides releasing silver followed by a slower breakdown of the iron matrix to liberate encapsulated minerals. The core breakthrough is the discovery that AgCl combines with chloride anions from the quaternary ammonium salt to form a unique inorganic helical chain structure. The stability of this helical assembly is attributed to an ordered CH…Cl^- H-bonded network. Spectroscopic characterization and theoretical calculations confirm that this network undergoes an energetically favorable reconstruction that overcomes the high lattice energy of AgCl. This finding demonstrates that the cooperative effect of weak H-bonds can dissociate covalently stabilized solids. Our study thus provides an innovative strategy for sustainable silver metallurgy and introduces a new paradigm of H-bond-directed metallurgical design.