Characteristics of strontium adsorption onto aquatic sediments in Southwest China

The adsorption of strontium (Sr) onto aquatic sediments plays a crucial role in regulating its environmental mobility and level of ecological risk. This study investigated the adsorption behavior of Sr onto selected sediments through batch equilibrium experiments, revealing that adsorption follows the Langmuir and the Freundlich equations. The adsorption temperature was positively correlated with the maximum adsorption capacity (Qm) of Sr onto sediments (R2: 0.78–0.88). As temperature increases, enhanced molecular kinetics promotes adsorbate diffusion and active site accessibility, resulting in a temperature-dependent augmentation of adsorption capacity (T: 277.15–308.15 K, Qm: 2926–12628 mg·kg− 1, an increase of 1.03–2.10 times). During the adsorption process of sediment, calcium ions (Ca2+) and strontium ions (Sr2+) exhibit significant competitive adsorption behavior. The results show that an increase ion strength significantly inhibits the adsorption capacity of Sr2+ (Ca2+ concentration: 0–0.05 mol·L− 1, the maximum inhibition decreased of Qm: 19.38 times). As the concentration of the equilibrium concentration (Ce) increased, the pH (pHf) values gradually decreased within the range of 7.05–6.35. The adsorption removal efficiency (R%) of Sr increased with the initial pH (pHi) (2.17%-49.65%). This study of the adsorption nature of sediments provides an empirical reference for the treatment of radionuclide contamination in sediments.