Effect Of Redox Potential On Adsorption And Migration Of Uranium At Water Rock Interface

In this paper,the uranium ore samples were taken from the decommissioned area in the in situ leach mine in Nothwest China,the sandstone uranium ore columns and soil column with different redox potentials were prepared to study the effect of redox potential on the adsorption and migration behavior of uranium at water rock interface;The effects of adsorption time,p H,temperature,particle size,initial concentration and eh on uranium adsorption were studied by static batch adsorption test.;Simulation tests of the infiltration of uranium solution through them were conducted,the concentrations of uranium and iron,redox potential(Eh),p H and electrical conductivity(Ec)of the effluents from the columns were measured,the contents and uranium species at different depths of the columns after the tests were analyzed,and the samples before and after the tests were characterized by SEM and FT-IR.(1)The batch static adsorption test of single factor shows that p H is the main factor affecting the adsorption of uranium.According to the experimental results,the optimal adsorption conditions were determined as follows:adsorption time was 6 h,the optimal adsorption temperature was 25?,the optimal p H was 5,the optimal particle size was 200 mesh,and the initial concentration was 20 mg/L.The results of static adsorption experiments under different redox potentials show that the adsorption capacity of uranium ore after leaching is as follows:original uranium ore>reduction uranium ore>oxidation uranium ore.(2)Through kinetic analysis,it is found that the pseudo second order kinetic model can better describe the adsorption process of sandstone uranium ore,indicating that the adsorption is mainly chemical adsorption.According to the thermodynamic analysis of uranium adsorption by uranium ore under different redox potentials,the fitting coefficient R~2 of Freundlich isothermal adsorption model for five types of uranium ore is higher than that of Langmuir isothermal adsorption model,which indicates that the adsorption of uranium by leached sandstone uranium ore is mainly heterogeneous adsorption under different redox potentials.(3)The migration rate of uranium in soil column under oxidation condition>migration velocity of uranium in soil column under original condition>migration rate of uranium in soil column under reduction condition.The migration rate of uranium in oxidized uranium ore sample is higher than that in original uranium ore sample and that in reduced uranium ore sample;Under the original condition and reduction condition,the main forms of uranium are residual state and carbonate bound state,with the residual state accounting for 48%?58%and 30%?49%respectively,and the carbonate bound state accounting for 27%?49%and 30%?49%respectively.Under the oxidation condition,the main forms of uranium are residual state,carbonate bound state and exchangeable state,with the proportions of 50%?60%,19%?27%and10%?15%respectively.(4)SEM analysis shows that the adsorption of uranyl ions mainly occurs on the surface of uranium ore during the infiltration process;the adsorption effect is the best under reduction condition,and the worst under oxidation condition;FT-IR analysis shows that the adsorption of uranium on original uranium ore and oxidized uranium ore is mainly due to the function of functional group oh and active groups C-O,C-H,Si-O-Si,while that on reducing uranium ore is mainly due to the effect of functional group oh and active groups C-O,C-H,Si-O-Si In addition to the function groups and active groups mentioned above,the adsorption of uranium on uranium ore has the function of C=O in ascorbic acid.