LLC Research Center Hydrometallurgy (Saint-Petersburg, Russia)

А. V. Khasanov, Leading Engineer, khasanov-a@gidrometall.ru
I. V. Fomenko, General Director, Candidate of Technical Sciences, fomenko-i@gidrometall.ru
S. Yu. Polezhaev, Senior Researcher, Candidate of Technical Sciences, polezhaev-s@gidrometall.ru
Ya. М. Shneerson, R&D Director, Doctor of Technical Sciences, shneerson-y@gidrometall.ru

The paper presents the results of long-term research conducted by the team of LLC Research and Engineering Center Hydrometallurgy aimed at improving gold recovery from double-refractory sulfide concentrates from the Malomyr deposit under the conditions of the Pokrovsky Autoclave Hydrometallurgical Complex. It has been demonstrated that the presence of organic carbon (0.49%) in combination with chloride ions causes a preg-robbing effect, reducing gold recovery during pressure oxidation. It has been established that increasing the chloride concentration from 5 to 26 mg/l decreases gold recovery from 96.1% to 92.3%. Three options for additional treatment have been investigated: preheating of the initial concentrate, oxidative roasting of the conditioned autoclave residue, and oxidative roasting of cyanidation tailings. It has been established that thermal treatment of the concentrate at 350 °C for 30 min increases gold recovery to 96.8% due to a reduction in the sorption activity of carbon. The most effective treatment turns out to be oxidative roasting of the autoclave residue and cyanidation tailings at 500 ± 50 °C for 60 min in an oxygen atmosphere. Under these conditions, gold recovery reaches approximately 99%, while the residual gold content in the tailings decreases to less than 1 g/t. A higher temperature (above 650 °C) causes partial melting of the calcine, formation of eutectics, and secondary encapsulation of gold, resulting in deterioration of the process performance. Based on the results obtained, a modification of the process flowsheet of the Pokrovsky Autoclave Hydrometallurgical Complex has been proposed. The most promising option is found to be the implementation of oxidative roasting of the autoclave residue, which provides high gold recovery without the need for repeated cyanidation, unlike the roasting of cyanidation tailings. Preliminary thermal treatment of the concentrate is found to be less effective. The recommendations developed make it possible to mitigate the preg-robbing effect, significantly reduce gold losses, and increase the complexity of processing refractory raw materials.

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