Systematic studies were conducted at one of the uranium deposits in Kazakhstan. Native strains of Acidithiobacillus ferrooxidans bacteria were found in leaching solutions at the deposit. The modeling of iron species in the culturing medium was analyzed using Medusa software v.2.0.5. To intensify the process, the bacterial strains were propagated in laboratory conditions, and strains available in the laboratory were added. The ability of bacteria to oxidize divalent iron to trivalent iron at 8 °C in laboratory conditions was established, but the oxidation rate was low. It was found that the limiting stage of bioleaching use in deposit conditions is the temperature mode, the content of divalent iron, and oxygen. A biomass volume of 15 L was initially cultivated under laboratory conditions, and subsequently scaled up to 3 m³ in production using three 1 m³ pachucas with air aeration. In addition, pilot tests were carried out directly in production conditions and biomass in the volume of over 30 m³ was produced. The kinetics of the oxidation process of divalent iron to trivalent iron in 1 g/h under production conditions was established. The features of the bioleaching process at the field are shown as follows: since production, the solution contains the main microelements for the nutrition and reproduction of bacteria, and recommendations for the use of bioleaching are proposed. Research has established that under conditions of a shortage of divalent iron in the solution, sulfuric acid is formed due to sulfur-containing substances. It was observed that for the effective conversion of divalent iron to trivalent iron, bacteria of the provided strain and air (oxygen) supply are sufficient. The corresponding recommendations were issued during the work.

This study presents findings regarding the kinetics of ferrous iron oxidation in solution mediated by Acidithiobacillus ferrooxidans bacteria within a continuous-flow bioreactor employing diverse types of immobilizers. The objective is to augment the rate of ferrous iron oxidation in solutions utilizing an immobilizer for Acidithiobacillus ferrooxidans strains. Immobilization represents a promising avenue for enhancing the efficiency of Fe²⁺ oxidation via acidophilic ferrooxidizing bacteria, leading to a several-fold increase in oxidation rate. A comparative analysis was conducted to evaluate the efficacy of different types of immobilizer in facilitating iron oxidation within a continuous-flow bioreactor, including the application of wood chips coated with Fe(OH)₃. The results indicate that wood chips coated with iron hydroxide serve as effective type of immobilizer, facilitating the robust attachment of Acidithiobacillus ferrooxidans via electrostatic interactions between negatively charged bacteria and positively charged surfaces. Experimental investigations were conducted using novel immobilization matrices in pilot-scale tests simulating the underground borehole leaching (UBL) of uranium. The bioactivation of leaching solutions enhances the efficiency and environmental compatibility of UBL compared to conventional chemical oxidation methods. The relationships between redox potential and ferric iron content in bioactivated solutions during the UBL of uranium were delineated. The significance of this study lies in its elucidating the pivotal role of Fe²⁺ oxidation in uranium extraction processes, particularly in the context of UBL. By employing bioactivation mediated by Acidithiobacillus ferrooxidans, the study demonstrates not only enhanced uranium extraction efficiency, but also markedly improved environmental sustainability compared to traditional chemical oxidation methods. The findings reveal crucial correlations between redox potential and ferric iron concentration in bioactivated solutions.

At one of the Kazakh uranium deposits, studies were carried out on the effect of ironoxidizing bacteria on the redox potential of leaching solutions. The studies carried out on three bioreactors with a volume of 1 m3 and one bioreactor with volume 6 m3 made it possible to establish a close relationship between the content of ferric iron in the solution and the redox potential of the leaching solution. In situ recovery of uranium uses sulfuric acid leaching solutions containing sulfuric acid from 3.5 g/liter to 25 grams/liter. Diagrams of the relationship between redox and the content of a trivalent iron in solution were obtained. This makes it possible to carry out an operational analysis of the composition of the leaching solution according to the redox of the solution directly in the conditions of the geotechnological field.

Technology of in-situ recovery (ISR) of uranium is using in Kazakhstan for increasing of production 15 times from 800 ton in 1998 till 22 000 ton in 2013. This ISR process is zero wastes technology. Investigations showed serious potential to improve results of ISR technology using biotechnology methods. Uranium in the ore body is usually presented as hexavalent (soluble) and tetravalent uranium (slightly soluble). To convert uranium into a soluble form, it is necessary to oxidize tetravalent uranium. Leaching solution of most of the uranium deposits of Kazakhstan contains ferrous iron. Oxidation of tetravalent uranium was obtained by the formation of ferric iron by iron-oxidizing bacteria A.Ferrooxidans. This bacteria oxidize ferrous iron till ferric iron. This was done at a uranium mine in two 20 m3 a flow bioreactors of new construction. In bioreactors was get activated leaching solution where take place oxidizing of ferrous iron. The redox of the leaching solution rose from 360 mV to 430-450 mV in bioreactors. The content of ferric iron increased from 0.1 g/l to 1.5 g/l and higher. Temperature of leaching solution was 10-140C in order to decrease cost for heating. Concentration of uranium in the productive solution increased by 20 % without adding additional sulfuric acid. Test with additional sulfuric acid give 40 % increasing of concentration of uranium in production solution. The costs of using the technology are 6-8 times lower in comparison with using chemical oxidizers (hydrogen peroxide).

Uranium mining companies of Kazakhstan during 15 years increased production of uranium more than 15 times using in-situ recovery of uranium (ISR). At the same time a significant part of uranium deposits contains gold, silver, palladium and rare metals like rhenium, germanium, scandium and et`s. The task was set for the complex extraction of associated metals from technological solutions of a uranium mine. Work was carried out to select and study samples of productive solutions and leaching solutions at one of the uranium mines in Kazakhstan. At the second stage, an experimental unit was installed in a 40-foot container (Stand), consisting of six sorption columns and two flow channel extractors. The hydrodynamic resistance of channel extractors much less then in sorption columns. This is a fundamental technical advantage compared to sorption columns. The flow rate in the Channel extractors was more than 0.85 m/sec, which is much higher than the flow rate in the sorption columns (0.01 m/sec). Enlarged tests were carried out with various types of ion-exchange resins, activated carbon, and zeolite on the Stand. Channel extractors used CYANEX extractants and others. It was showed the potential for extracting associated valuable metals from technological solutions: gold, scandium, germanium and other metals. Integrated mining of associated metals at the explored uranium mine of Kazakhstan will provide an economic benefit of up to $350 million.