National University of Science and Technology “MISiS”, Moscow, Russia:

L. N. Krylova, Leading Researcher of a Chair of Concentration of Non-ferrous and Rare Metals' Ores, e-mail: krulov@yandex.ru
K. A. Vigandt, Post-Graduate Student of a Chair of Concentration of Non-ferrous and Rare Metals' Ores

E. V. Adamov, Head of Department of “MISiS” Publishing House
Zheng Zhi Hong, Post-Graduate Student of a Chair of Concentration of Non-ferrous and Rare Metals' Ores

Peoples' Friendship University of Russia, Moscow, Russia:

L. E. Sarukhanova, Assistant Professor of a Chair “Microbiology and virology”

The advantages and disadvantages of technologies of vat biooxidation of sulfide concentrates are summarized, regarding the alternative hydrometallurgical autoclave leaching technologies, at atmospheric pressure with application of various reagents. Application of bacterial leaching has the following technical and economic advantages:
— small consumption of reagents;
— higher reactivity and rate of solids deposition in bacterial solutions (compared with solutions without bacteria);
— acceleration of bacteria oxidation of formed elemental sulfur;
— easiness of maintenance;
— low operating and capital costs, etc.
The long duration of the process is the main disadvantage of application of biooxidation technology. There are presented the results of research and technological solutions, based on the modern ideas of operation of iron-oxidizing bacteria on mineral raw materials, which implementation is conductive to significant increasing of efficiency of sulphide concentrates' biooxidation technologies, applied in industry. Increasing of the grade of oxidation of concentrate sulfides and gold recovery is possible due to the following operations:
— release of oxidized slime fraction of gold-bearing sulfide concentrate after 60–90 hours of bacterial leaching by classification in hydrocyclone;
— final leaching of the most refractory sulfides.
Carrying out the oxidation of sulfides by bacterial solutions separately from bacterial regeneration of iron (III) makes it possible to create the optimal conditions for each process and, as a result, to reduce the duration of biooxidation from 120–150 to 10–20 hours. During the use of immobilization of ironoxidizing bacteria on a neutral carrier for iron (III) regeneration, the amount of biomass increases significantly together with increasing of iron oxidation rate to 10–20 g/(l·hour). According to this, the cell resistance to adverse environmental factors is increased together with bacterial oxidation efficiency.

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