Study On The Effect Of Iron Precipitation On Uranium Fixation Rate In Groundwater By Acid In-situ Leaching And Its Mechanism

As an important strategic resource of nuclear energy in China,uranium is essential.At the same time,uranium is highly toxic and radioactive,which will seriously pollute the groundwater environment in mining areas and pose a great threat to human health.Fe has a significant effect on the removal,migration and transformation of uranium in groundwater,and the content of Fe is rich.In order to study the effect of iron hydroxide precipitation on Uranium Migration in in-situ leaching well site after final mining,batch experiments were carried out to study the effects of p H,iron concentration,Fe²⁺/ΣFe ratio,coprecipitation kinetics of iron and uranium,as well as the changes of iron ion morphology,p H and Eh with reaction time.The effects of iron mineral precipitation on uranium in solution under different environmental conditions were discussed by means of SEM,EDS and XPS.The effect of immobilization efficiency,stability and mechanism of action.The results show that:The immobilization efficiency of uranium increases significantly with the increase of p H from 2 to 7,and the immobilization rate of uranium by iron hydroxide precipitation can reach more than 96%when it is neutral.The removal efficiency of uranium by Fe³⁺is higher than that by Fe²⁺.When the ratio of Fe²⁺/ΣFe is 0.5,0.75 and 0.83,the fixation rates of uranium by iron hydroxide precipitation are 97.21%,96.68%and96.14%,respectively.When p H<5,the uranium on the iron ore can be desorbed,and when p H>5,the iron uranium coprecipitation remains stable.The kinetic experiments in neutral solution show that coprecipitation dominates the fixation mechanism of iron on uranium,and the sedimentation rate of U（VI）increases by about 30%in aerobic environment.The pseudo first order,composite second order and Elovich kinetic models are used to describe the adsorption mechanism of uranium by iron hydroxide precipitation,which is mainly non-uniform surface adsorption affected by activation energy.SEM,EDS and XPS analysis further confirmed the synergistic effect of coprecipitation and heterogeneous surface adsorption,and the fixed form of U（VI）in iron hydroxide precipitation was mainly U（VI）,a small amount of which was reduced to U（V）,U（VI）accounted for 74%-81.2%,U（V）accounted for18.8%-26%.Based on the above,combined with the content of iron in groundwater after final mining in acid in-situ leaching area,this paper explores the dynamic influence of iron on uranium fixation and stability under different environmental conditions,which is helpful to understand the fate of uranium in the underground environment and provide a reference for the decommissioning treatment of groundwater pollution.