SILVER LOSSES FROM AMMONIACAL SOLUTIONS ON COMPLEX SULFIDE AND CHALCOPYRITE AMMONIA LEACH RESIDUES

The lost silver value from the leach liquor was unrecoverable when the residues were treated with ammonia-ammonium sulfate buffer (pH equals 9. 5) solutions at 27 degree C. However, when the same slurry was heated to 75 degree C in an autoclave under an atmosphere of oxygen, almost all the silver value could be redissolved. The leach residues lost their silver absorbance property from ammoniacal solutions on repeatedly heating and cooling the leached slurries in the presence of oxygen. In this work, silver losses from ammoniacal solutions on various leach residues, synthetic iron oxides, and freshly precipitated Fe(II) and Fe(III) hydroxides are reported. None of the major constituents presented in the leach residues were responsible for the silver losses but small amounts of Fe(II) could take up silver from the leach solutions.