Carbon dioxide will help gold mining
Scientists from the Institute of Biotechnology of the Russian Academy of Sciences have determined that the additional supply of carbon dioxide to bioreactors with microorganisms oxidizing sulfide minerals helps to increase the efficiency of gold extraction at elevated temperatures. This may make it possible to optimize the industrial technologies used to extract gold from sulfide ores, writes the journal Biology.
Thermoacidophilic microorganisms, bacteria and archaea, active in a very acidic environment at elevated temperatures (about 40-50 ° C), are used on an industrial scale to extract gold from stubborn gold—containing sulfide ores. These microorganisms oxidize sulfide minerals, which causes the latter to break down, releasing the gold particles contained in them.
Earlier studies have shown that the activity of microbial biooxidation in reactors depends on which compound is used as a carbon source for microorganisms. Carbon dioxide, limestone, molasses and yeast extract can be used for this purpose. However, it is not completely clear how the excessive introduction of carbon sources and their composition affects the activity of microbial communities and the process of biooxidation.
Scientists of the Institute of Biotechnology of the Russian Academy of Sciences compared the bioxidation activity of sulfide gold—containing concentrate by acidophilic microorganisms at different temperatures and carbon sources to understand how these factors affect the rate of oxidation of gold-containing sulfide minerals - pyrite and arsenopyrite. The experiments were carried out at three different temperatures: 40 °C, 45 °C and 50 °C. In addition, the effect of different carbon sources — carbon dioxide and molasses - was also studied for each of the selected temperatures.
It turned out that at a temperature of 40 °Using additional sources of carbon — excess carbon dioxide and molasses — practically does not affect the ability of the microbial population to oxidize minerals. However, when the temperature rises to 45°Differences in the activity of biooxidation were observed between C and 50 °C, and the use of carbon dioxide led to an increase in the degree of oxidation of pyrite and arsenopyrite. At the same time, in the control experiment without additional carbon sources, the oxidation activity of sulfide minerals significantly decreased compared to 40 °C, whereas the use of carbon dioxide made it possible to neutralize this negative effect of elevated temperature on the oxidation of sulfide minerals and gold extraction.
According to the authors, the observed effect may be explained by the effect on microbial populations of bioreactors. The use of additional carbon sources at elevated temperatures led both to an increase in the total number of microorganisms and to changes in the composition of populations.
"Our study demonstrates that the additional supply of carbon dioxide to reactors helps to increase the efficiency of biooxidation of minerals by microbial communities and at the same time prevents the suppression of biooxidation at elevated temperatures, which is a typical problem for industrial reactors," said Alexander Bulaev, Candidate of Biological Sciences, Head of the Laboratory of Chemolithotrophic Microorganisms of the Institute of Biotechnology of the Russian Academy of Sciences.
The study was carried out within the framework of the RNF 21-64-00019 project "Metagenomic analysis and engineering of microbial consortia for industrial microbiology".
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