Research into the Percolation Leaching of Copper and Silver from Stale Tailings

Silver extraction by percolation leaching on a pelletized sample of stale tailings with the organic binding agent Alcotac^® CB6 is studied. A column 0.5 m high and 56 mm in internal diameter was used for laboratory tests on percolation leaching. Pelletization was carried out in a drum-type granulator with the Alcotac^® CB6 reagent (BASF, Germany) consumption of 800 g/t; the moisture content of the granules was 8–10% with a size of 8–10 mm. The composition of the samples was determined based on the data of optical and electron microscopy, X-ray diffraction, local X-ray spectral, X-ray fluorescence, and mass spectrometry with inductively coupled plasma. Stale tailings of the Zhezkazgan enrichment plant (Ulytau region, Republic of Kazakhstan) were examined, in which the main part of copper is represented by oxidized minerals (78.47%); content of sulfide minerals is 21.53%. The results of physicochemical studies with the determination of the material composition of the sample and observations on the percolation leaching of copper and silver from the stale tailings of Zhezkazgan are presented. The copper leaching was studied in two stages using a sulfuric acid solution as a solvent. The next stage was the transfer of silver into the solution by cyanidation. Copper extraction into the solution was 88.55% with a sulfuric acid consumption of 80.0 kg/t of tailings, and that of silver was 75.31% with a sodium cyanide consumption of 0.55 kg/t. The studies of two-stage leaching showed the effectiveness of preliminary pelletizing of stale tailings with the Alcotac^® CB6 reagent. In the process of leaching, the pelletized material features sufficient porosity and permeability and provides access of cyanide solutions to the surface of precious metals.