Leaching Technology And Mechanism Research Of Low-sulfur Uranium Bioleaching Enhanced By Pyrite

Granite type uranium deposit is a major uranium resources in China,however,extent of uranium bioleaching has been restricted by low associated pyrite in the uranium ore.Adding exogenous pyrite is an efficient way for the enhancement of uranium bioleaching.In this study,granite type uranium ore was used for the research of uranium bioleaching enhanced by adding pyrite,providing the optimal conditions for column bioleaching of uranium ore.In this process,changes of key parameters,uranium ore,pyrite and microbial diversity were intently monitored and determined,and the mechanism of uranium bioleaching enhanced by adding pyrite was revealed with studying the behavior of microorganisms and the effect of iron and sulfur for uranium bioleaching.The following results were achieved.(1)The mineralogical properties of uranium ore and pyrite were identified.The quartz and silicate were dominant in uranium ore,and the content of alkaline minerals and associated pyrite are relatively low.Uranium,dominated by pitchblende,was mainly embedded in cracks and pores of quartz and silicate,which is not conducive to bioleaching of uranium.YF pyrite was dominated by pyrite,followed by minerals e.g.hydroferric vanadium,quartz,gypsum.EPMA analysis suggested that a small amount of zinc sulfide was observed in YF pyrite,forming a galvanic cell with pyrite to accelerate the dissolution of pyrite.(2)The optimal conditions of uranium bioleaching were obtained.The extraction of uranium bioleaching enhanced by YF pyrite was obviously better than that of FS pyrite and DBS pyrite.In addition,temperature,pyrite addition ratio and liquid-solid ratio also had a greater impact on uranium bioleaching.Under the conditions of a temperature of 30?,a liquid-to-solid ratio of 20:1 and a YF pyrite addition of 2%,the extraction of uranium bioleaching was as high as 97.02%.(3)The improved ability of YF pyrite and the change of microbial community during the column leaching process were investigated.After adding YF pyrite,the acid consumption decreased from 27.09g/Kg to 24.35g/Kg,and the uranium extraction increased from 88.16%to 92.92%.The results showed that adding pyrite was in favor of the reduction of acid consumption and the enhancement of uranium bioleaching.The results of microbial diversity suggested that the dominant genus in the ore and leaching solution at different leaching stages changed significantly,and adding pyrite was conducive to promote the transfer of At.f in the leachate to the surface of ore.At the same time,the abundance of key genes was significantly increased.XRD results indicated that uranium ore at different leaching stages was mainly composed of stable SiO₂ and KAlSi₃O₈,with a small amount of calcium silicate and other precipitates.SEM-EDS results showed that a loose structure and serious surface corrosion were observed in the uranium tailings,and the uranium ore was attacked by biochemical action,contributing to the release of uranium.(4)The mechanics of uranium bioleaching enhanced by pyrite was initially revealed.The results suggested that the ability of At.f transfering to the uranium ore was improved,because of lacking of Fe²⁺and S in the leaching solution and searching for energy substances.Under the action of At.f,elemental sulfur was oxidized to sulfate to provide sufficient acid for the leaching system,contributing to the reduction of Ca SO₄ precipitation and the enhancement of uranium chemical leaching.SEM-EDS results showed that At.f tended to adhere to the surfaces and surroundings of rough jarosite and other precipitated.Q-PCR results showed that the number of planktonic At.f and attached At.f was improved significantly with adding iron and sulfur.CLSM results showed that the content of EPS increased strongly by the stimulation of iron and sulfur,contributing to uranium bioleaching by enhancing the contact between At.f and minerals.