Industrial application of bacterial iron oxidation in in-situ leaching technologies for uranium

Abstract

A technology for bacterial iron oxidation in the process of in-situ leaching of uranium has been developed and proposed for industrial use. The technology was validated by the results of pilot tests conducted at a uranium deposit in Kazakhstan over a period of 12 months. The aim of the study was to develop a technology for bacterial iron oxidation in the process of in-situ uranium leaching using a new type of flow bioreactor. Two biotechnological installations with bioreactors of 20 m³ volume were created and installed in 40-foot containers. The bioreactors, equipped with piping, air compressors, a pumping station, and control and measuring instruments, were installed at the geotechnical site and connected to the main in-situ uranium leaching system through wells. The installations had a productivity of over 150,000 m³/year for the leaching solution. After passing through the bioreactors, the redox potential of the solution increased from 360 mV to 430-450 mV in flow mode. The concentration of ferric iron increased from 0.1 g/L to 1.5 g/L and higher. The bacterial iron oxidation process was carried out at a solution temperature of 10 to 12°C (optimal temperature — 25-35°C), which allowed eliminating the costs of heating the solution. The test results showed an increase in uranium content in the productive solution by 10-20% after the leaching solution passed through the ore-bearing layer for 1 month. This confirmed the prospects for using this technology for in-situ well uranium leaching. The economic costs of using the technology are 6-8 times lower compared to using chemical oxidants such as hydrogen peroxide. The obtained industrial results open new prospects for the application of biotechnological methods for in-situ well leaching of uranium and other metals for the first time.