Bentonite-goethite composite Colloids: Unraveling the mechanisms of strontium adsorption inhibition in claystone for nuclear waste geologic repositories.

The management and disposal of radioactive waste, especially strontium (Sr), is a critical aspect of sustainable nuclear energy utilization. This study examines the adsorption of Sr onto the surrounding rock of a high-radioactivity geological repository, with a specific emphasis on the Suhongtu claystone and its interaction with bentonite‒goethite composite colloids. By utilizing a sequence of static adsorption experiments, adsorption kinetic models, and diverse spectroscopic methods, this research aims to shed light on the adsorption mechanism of Sr influenced by these composite colloids. These results indicate that the claystone adsorption capacity for Sr is considerably affected by pH and that the adsorption rates are elevated in alkaline environments. The bentonite-goethite composite colloid formed a protective layer on the surface of the plagioclase in the claystone, hindering ion exchange between the strontium and the surface of the plagioclase and thus inhibiting strontium adsorption by the claystone. This study offers profound insights into the function of composite colloids in the adsorption process and has potential implications for the design and safety evaluation of radioactive waste repositories.