Behavior and Mechanism of Uranium Adsorption on Soil Medium Nearby Radioactive Waste Disposal Sites
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Abstract
The adsorption of radionuclides in soil media has become one of the key considerations in both site selection and safety evaluation of geological repository. In order to understand the adsorption behavior and mechanism of uranium on soil media from pre-selected sites of radioactive waste disposal sites, batch adsorption experiments were adopted to study the adsorption of U(VI) on mineralogical components in Shenzhen(SSD) soil and Yangjiang(YJ) soil. The effects of initial concentration of U(VI) and ionic strength were studied in detail and the adsorption mechanisms were discussed by kinetic model and isothermal adsorption model. The results show that the equilibrium absorption capacity of U(VI) on both SSD soil and YJ soil increase when the initial concentration of U(VI) increase, while the removal rates of U(VI) on SSD soil and YJ soil decrease from 97.07% and 91.56% to 88.55% and 87.93%, respectively. The adsorption of uranium is not sensitive to ionic strength, which indicates the major species form on SSD soil might be inner-sphere surface complexes. The pseudo-second-order kinetic model and Langmuir isothermal adsorption equation can be used to describe the adsorption of U(VI) on both SSD and YJ soil media, and all the relation coefficients are higher than 0.99. This work provides some guidance for further study of actinides adsorption model on the soil medium, and offers the basis to speculate the transport behavior of uranium in the environment.
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