In cave disposal environment, surrounding rock is the last barrier to prevent radionuclides from entering the environment, and the colloid of surrounding rock produced in the long-term disposal process increases the risk of radionuclides migration.

This study aims to explore the adsorption performance of surrounding rock colloid for Sr²⁺ disposed the repository, and the stability of surrounding rock colloid.

First of all, the surrounding rock colloid sample was prepared with approximate mass concentration of 0.03 g·L^-1, zeta potential of 21.53 mV and particle size of 205.7 nm. Then, the effects of time, pH value, various ions under different concentrations, and other factors on the adsorption properties, such as the zeta potential and average particle size of the surrounding rock colloids were investigated by experimental measurements. Finally, the adsorption kinetics and adsorption isothermal model were analyzed.

Experimental results show that the colloid adsorption Sr²⁺ reaches equilibrium at 12 h, and the equilibrium adsorption capacity is 41.79 mg·g^-1. In alkaline environment, the adsorption capacity increases with the increase of pH. The adsorption of Sr²⁺ by colloid of surrounding rock is inhibited by different ions, and the inhibitory effect of cations is greater than that of anions.

Results of this study indicate that pH value, temperature and partial ions in the groundwater of the cave disposal facility all have influence on the stability of surrounding rock, and the surrounding rock colloid has good stability in the groundwater environment of the repository. The adsorption of Sr²⁺ by surrounding rock colloid conforms to the quasi-second-order kinetic model and the Freundlich adsorption isothermal model.