Nitric acid leaching of silver sulphide precipitates

• Published in: Hydrometallurgy Vol. 74; no. 3; pp. 213 - 220
• Main Authors: Holloway, P.C., Merriam, K.P., Etsell, T.H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-10-2004; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Hydrogen reduction; Metals. Metallurgy; Nitric acid; Photographic solutions; Pressure leaching; Production of metals; Secondary recovery; Silver; Silver sulphide; Silver; Secondary recovery; Pressure leaching; Photographic solutions; Silver sulphide; Nitric acid; Hydrogen reduction; Lixiviation; Precipitation; Precipitate; Hydrometallurgy
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/j.hydromet.2004.05.003

Leaching of silver sulphide precipitates with nitric acid was performed at a variety of temperatures, pressures, acid concentrations and solids concentrations, with a maximum extraction of 96.1% achieved by leaching at 150°C, 1100 kPa(g), and 9.6% solids with twice the stoichiometric amount of nitric acid. Further improvement in the silver extractions would be expected with further optimization of the leaching conditions and this process could represent a hydrometallurgical alternative for the recovery of silver from silver sulphide precipitated from photographic solutions.
Hydrogen reduction from nitric acid leach solutions resulted in near quantitative precipitation of silver (99.8%) in 1 h at 150°C and 4000 kPa(g) hydrogen pressure. High precipitation efficiencies with hydrogen reduction were achieved even at silver concentrations well in excess of the solubility limit for silver sulphate at room temperature. High purity silver with a particle size of 96.2% passing 106 μm was produced.