Oxidation Mechanism Of Acidithiobacillus.ferrivorans And Its Application In Acid In-situ Leaching Of Uranium

Fe³⁺is a natural oxidant,which can oxidize U⁴⁺to U⁶⁺.Increasing the concentration of Fe³⁺in leaching solution can accelerate the leaching rate of uranium in acid in-situ leaching.Acidithiobacillus ferrivorans(A.ferrivorans for short)is a kind of low temperature tolerant inorganic autotrophic uranium leaching microorganism,which can oxidize Fe²⁺to Fe³⁺.Using A.ferrivorans as oxidant instead of hydrogen peroxide in traditional uranium leaching process to oxidize Fe²⁺in adsorption tail liquor can reduce the consumption of oxidant.Therefore,in this paper,the oxidation experiment of A.ferrivorans on pyrite and Fe²⁺in acidic environment was carried out,the oxidation mechanism of A.ferrivorans was studied,and the stage model of A.ferrivorans oxidation of pyrite was put forward.Then,a new high-efficiency bioreactor was designed and constructed in an acid in-situ leaching mine in Xinjiang,in which A.ferrivorans was used as oxidant instead of hydrogen peroxide,a field scale-up test of A.ferrivorans rapid oxidation the Fe²⁺in adsorption tail liquor of in-situ leaching of uranium was carried out.The research results are as follows:(1)The experimental study on the oxidation mechanism of A.ferrivorans showed that:1)pyrite can be used as the energy source of A.ferrivorans,and iron in the pyrite can be oxidized into the solution faster with the action of A.ferrivorans.A.ferrivorans+pyrite or Fe³⁺+pyrite system,the oxidation effect of pyrite was not obvious,the oxidation process did not produce precipitation;In A.ferrivorans+Fe³⁺+pyrite and A.ferrivorans+Fe²⁺+pyrite systems,the oxidation effect of pyrite was obvious,and a large amount of precipitates jarosite would be produced.A.ferrivorans promoted the formation of jarosite,which in turn accumulate and covered the mineral surface with S-related oxides,preventing further leaching of the metal.2)Adding different amounts of pyrite into A.ferrivorans bacterium fluid+9K medium(Fe²⁺concentration was 1 g/L)system showed that the higher the addition amount of pyrite,the higher the concentration of?Fe in the solution.The addition of pyrite in microbial leaching system can inhibit the formation of jarosite,and the greater the addition amount of pyrite,the more obvious the inhibition effect.3)when Fe³⁺and Fe²⁺were present in the initial environmental system under acidic conditions,there were four stages of A.ferrivorans oxidation of pyrite,and a model of A.ferrivorans oxidation stage of pyrite was established.(2)A new type of high-efficiency bioreactor with 7.0 m in height,2.0m in inner diameter and 17.8 m³ in total volume was designed and constructed in a uranium mine of Xinjiang,porous acid resistant ceramsites were selected as the carriers of bacteria,and the Fe²⁺in the tail liquor of in-situ leaching of uranium by Acidithiobacillus ferrivorans immobilized on the carriers at low temperature,to carry out an extended experimental study.The results showed that the maximum flow rate of bioreactor was28.2 m³/h when Fe²⁺concentration was 200?300 mg/L and aeration rate was 59.0 m³/h under the condition of 5?24?in the field,and the Fe²⁺in the tail liquor could be oxidized rapidly and completely when the Eh(Redox potential)was above 570 m V;The bioreactor's maximum oxidation tail flow rate was expected to increase further if conditions continued to be optimized.(3)The bacteria in the field test bioreactor replaced hydrogen peroxide as the oxidant,and the annual saving cost was about 146,290 yuan,with a saving percentage of 77.24%.