Investigation of plutonium adsorption by geological materials in China’s radioactive waste repository disposal environment

The investigation elucidated the impact of pH and ions on the adsorption behavior of Pu(IV) by clay rock and bentonite, two pivotal geological barriers for disposal. Pu(IV) adsorption demonstrated a pronounced dependence on pH. In acidic environments, the adsorption of both clay rock and bentonite was markedly inhibited. Various ions exhibited inhibitory effects on the adsorption. Specifically, the inhibitory effect of Fe³⁺ was ascribed to the immobilization of Fe³⁺ hydrolysis products and competitive adsorption. Simultaneously, Pu(IV) formed complexes with both CO₃²⁻ and HCO³⁻, hindering the adsorption. Consequently, it is recommended that radioactive waste repositories maintain a low-carbon and iron-salt environment.