Mechanistic Studies Of Radionuclide Migration In The Modified Medium

⁸⁷Sr is the stable isotopes of the representative radionuclide strontium in radioactive waste. The migration mechanism of 87Sr in surface-modified media was studied in this paper. Firstly, quartz sand surface was modified via hydroxylization and silanization treatments to obtain hydrophilic and hydrophobic surfaces. Then, sorption and retardation characteristics of strontium in these modified quartz sand medium were studied by batch tests and column experiments to evaluate the distribution coefficient (Kd) and retardation factor (Rd) of this element in porous media. Finally, the Kd-parameters resulting from dynamic experiments were also compared with the results of static sorption experiments.The effect of the solute initial concentration,the liquid-solid ratio, pH, medium on distribution coefficient of strontium in modified quartz were investigated by batch experiment method. The results indicated that Kd Values of strontium was changed with wetting properties of quartz sand surface: ordinary quartz sand, 2.48ml/g; hydrophilic quartz sand, 2.77ml/g; hydrophobic quartz sand, 1.17ml/g, and the better wettability of quartz sand, the stronger adsorption was observed.The column tests include Br- disperiment and strontium migration experiments. The breakthrough curves, actual column flow rate, effective porosity, strontium retardation factor and distribution coefficients were also investigated. The results showed that migration velocity of Sr in ordinary quartz sand was 0.091m/d, retardation factor was 3.34, distribution coefficient was 0.257mL/g; in hydrophilic quartz sand, migration velocity of Sr was 0.086m/d, retardation factor was 3.44, distribution coefficient was 0.293ml/g; in hydrophobic quartz sand, the migration velocity was 0.183m/d, retardation factor was 1.83, distribution coefficient was 0.091ml/g. The radionuclide migration was effected by the wetting properties of the medium: the stronger the wettability of medium, the slower radionuclide migration. In conclusion, the Kd value of Sr from the batch tests was found to be higher than these from the column experiments.