BIOACTIVATION OF LEACHING SOLUTION FOR URANIUM IN-SITU RECOVERY

Abstract

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).