Heap sulphuric-thiocyanate leaching of gold and uranium

Abstract

The article evaluates the main parameters of simultaneous heap leaching of gold and uranium from oxidised gold-uranium ore using sulphuric acid thiocyanate solutions. Pilot tests for the simultaneous heap leaching of gold and uranium were carried out using oxidised crushed gold-uranium ore with a size of -40+0 mm. The gold and uranium content in the ore was 0.80 and 266 g/t, respectively. Experiments were carried out using a percolation column with a diameter of 300 mm and a height of 2000 mm The ore mass in the column was 180 kg. The temperature during the tests was in the range of 17–25°C. Leaching was carried out under the following conditions: H2SO4 concentration – 5 g/dm3, SCN– concentration – 0.5 g/dm3, Eh – 490–510 mV, Fe3+ ion concentration – 1.0–1.5 g/dm3. Acid-soluble minerals contained in the ore comprised the source of iron ions. Hydrogen peroxide was used to oxidise Fe2+ ions. Pilot tests were carried out in a closed cycle with separate sorption of gold and uranium. Based on the research results, gold recovery reached 90%, while uranium recovery was 55%. Following gold and uranium leaching, the loaded activated carbons and ion exchange resins were obtained. It was established that the gold content on activated carbons was 0.5–0.6 mg/g, while the uranium content on ion exchange resins amounted to 30–35 mg/g. The reagent consumption was as follows: H2SO4 – 10.5 kg/t, KSCN – 0.94 kg/t, H2O2 – 0.65 kg/t. It is shown that the technology for simultaneous heap leaching of gold and uranium with sulphuric acid thiocyanate solutions offers efficient processing of the ore. The recovery rates of gold and uranium are comparable to those obtained during pilot tests for heap leaching of the ore using conventional technology, involving the individual twostage leaching of these metals using sulphuric acid and cyanide solutions.