Development of a technique for the cavitation treatment of gold-bearing ores in an alkaline environment for the purpose of the associated extraction of platinoids from black shale ores

Abstract

Introduction: The most important task of improving the technology of extracting gold and platinum group metals (PGM) is the study of their behaviour under cavitation impact on black shale type and low-sulphide formations. In order to solve this problem, a concentrate for the cyanidation of the Golets Vysochaishy deposit was used as the test material. Methods: Supergrinding and dissolution in alkaline solutions was carried out on a cavitation rotary-type dispersant generator (Russia) with constant measurement of temperature, time, and pH of the medium. Determination of valuable components was carried out using atomic absorption spectrometer KVANT- Z.ETA-1 (OOO Kortek, Russia). Electron probe microanalysis with scanning electron microscopy was performed using JSM-6510LV electron microscope (JEOL Ltd., Japan) with an INCA Energy 250 microanalysis system (Oxford Instruments, UK). Sample preparation of the experiment was according to generally accepted method: in a mixture of nitric and hydrochloric acids (aqua regia), physical characteristics according to GOST 5180-2015. The pH measurement was carried out using a pH-150 MI pH-meter (NPO Izmeritelnaya Tekhnika, Russia). Results and discussion: Data on the solubility of gold and PGM in an alkaline medium during cavitation treatment were obtained. During total cavitation treatment for 25.5 min, 50% of platinum dissolved in the solution (content in the solution was 2.40 g/t, the initial content was 4.81 g/t), 76–87% of palladium dissolved in the solution (content in the solution was 4.67–4.00 g/t, the initial content was 5.27 g/t) and 22–30% of gold dissolved in the solution (content in the solution was 0.35–0.48 g/t, the initial content was 1.59 g/t). Conclusions: During cavitation treatment gold practically did not dissolve in the solution, while PGM showed good solubility. The application of this method in an alkaline environment will allow to recover PGM with simultaneous neutralization of cyanides from cyanidation tailings. The tailings storages can be considered as technogenic deposits of platinum and palladium. The optimal parameters for alkali consumption (134 g per 10 l of pulp) and processing time (17–19 min) were determined. The thermal power of the cavitation unit was calculated (7.7 kW).