Study on cesium adsorption behavior of mineral colloid in surrounding rock of cavern disposal repository

[Background]: The surrounding rock of the repository is the last barrier to block the migration of radionuclides, and there is a potential risk of co-migration of mineral colloid and nuclides in the fissure. [Purpose]: This study aims to investigate the main components of the surrounding rock mineral colloid and its adsorption mechanisms for Cs+, as well as to assess the co-migration risk of mineral colloid and Cs+. [Methods]: The chemical composition and microscopic images of SRM colloid were investigated by XRF, XRD, FT-IT, SEM and other characterization methods. The adsorption performance of SRM colloid for Cs+ was investigated by adsorption experiment, and the influence of groundwater characteristics on the stability and adsorption performance of SRM colloid was investigated. [Results]: The main components of SRM colloids were silicate minerals. The results of adsorption experiments show that the saturated adsorption capacity of SRM colloid for Cs+ is 47.07 mg·g-1. Strong acid and high concentration of K+ and Ca2+ will reduce the stability of the colloid, and the adsorption of Cs+ by SRM colloid will decrease. In the alkaline environment, the colloid stability is improved, and the adsorption amount of SRM colloid for Cs+ is increased. Conclusions: Conclusions: Mg2+ can promote the adsorption of Cs+ by SRM colloid by changing the microstructure of SEM colloid. [Conclusions]: Experimental results show that SRM colloid can carry Cs+ to co-migration, and can reduce the risk of co-migration by changing the pH of backfill materials.