Study of adsorption characteristic of uranium (VI) on clay colloid

[Background] At present, the study of surrounding rocks for high-level radioactive waste disposal is mostly clay rock minerals, but little attention has been paid to the migration mechanism of nuclide related to clay colloid. [Purpose] This study aims at the adsorption behavior of U (VI) on clay colloid and analysis of the adsorption mechanism of clay colloid on U (VI). [Methods] The static adsorption method was used to evaluate the adsorption capacity of clay colloid for uranium by the adsorption partition coefficient K_d. Effects of initial Uranium concentration, pH value and ion species on adsorption behavior of clay rock colloids were investigated. [Results] The results showed that the optimum of adsorption initial concentration is 3 μg · mL^-1. When the pH value is less than 8, the partition coefficient increases, and when the pH is 8, the sorption of U (VI) on clay colliod reaches the maximum value. To a certain extent, the adsorption of U (VI) in clay rock colloids was inhibited by anions and cations, among which Ca²⁺, HCO₃^-, CO₃^2- have strong inhibition effect. [Conclusions] The adsorption isotherms of U (VI) on clay colloid were well fitted by the Freundlich isotherm equation. Fourier transform infrared spectroscopy (FT-IR) indicates that the main groups before and after adsorption are hydroxyl groups. (authors)