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
К. М. Falin, Senior Engineer, falin-k@gidrometall.ru
S. Yu. Polezhaev, Senior Researcher, Candidate of Technical Sciences, polezhaev-s@gidrometall.ru

The most common cause of refractoriness in gold-bearing ores and concentrates is the fine dissemination of gold in sulfide minerals, primarily pyrite and arsenopyrite. Some types of such materials contain naturally occurring carbonaceous matter (CM), which is capable of adsorbing dissolved gold during subsequent processing. This phenomenon is known as preg-robbing. Specialists from LLC Research Center Hydrometallurgy have developed a method for reducing the sorption activity of carbonaceous matter, which involves oxidative roasting of autoclave oxidation products. The technology has been successfully tested on a laboratory scale. Refractory concentrates from various deposits in Russia and Kazakhstan, containing 0.3-5.0% organic carbon, have been investigated. The experiments have been conducted in two stages: the first stage has involved autoclave oxidation of the gold-bearing sulfide concentrate, while the second stage has involved roasting of the autoclave residue. The autoclave oxidation parameters have been as follows: temperature – 225°C and excess pressure – 3.25 MPa. The effects of roasting temperature, material residence time in the furnace, and consumption of an additional oxidizing agent on the process have been investigated. It has been established that the roasting technology for autoclave residues provides high and stable gold recovery during subsequent cyanidation of the calcine, even with significant variations in the carbonaceous matter content of the initial concentrates. Deep decomposition of the carbonaceous matter has been achieved by introducing an additional oxidizing agent during roasting. The proposed technology provides a universal solution to the problem of pregrobbing and can be recommended for implementation at facilities employing autoclave oxidation. The technology is unique and protected by Russian Federation Patent.

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