Effect of monovalent and divalent ion solutions as washing agents on the removal of Sr and Cs from soil near a nuclear power plant

Highlights: • Solutions of monovalent and divalent ions were used in Sr and Cs removal from soil. • Ca²⁺ and K⁺ solutions showed Sr and Cs removal rates of 68.2% and 81.3%, respectively. • Except for the residual forms, all other forms of Sr and Cs were extensively removed. • An ion-exchange mechanism was suggested for the removal of Sr and Cs from soil. Solutions of monovalent and divalent ions, including calcium, magnesium, ammonium, and potassium, were tested in the removal of Sr and Cs from soil near a nuclear power plant. The Ca²⁺ and K⁺ solutions exhibited removal efficiencies of 68.2% and 81.3% for Sr and Cs, respectively. This high performance was probably due to the physicochemical similarities between 'Ca and Sr' and 'K and Cs'. Alternatively, the Mg²⁺ and NH₄⁺ solutions performed much worse, despite having the same valences as Ca²⁺ and K⁺, respectively. Ca²⁺ and K⁺ solutions could also simultaneously remove cationic toxic metals present with the nuclides, albeit much less efficiently (30–40%). For anionic metalloid As and anionic toxic metal Cr, the efficiency was even lower (2+ and K⁺ solutions^, respectively. For comparison, widely used washing agents exhibited removal efficiencies of 25–30%. Notably, Fe²⁺ and Mn²⁺ ions were hardly detected in the Ca²⁺ solution, while their concentrations were much higher in the common washing agents, suggesting the involvement of an ion-exchange mechanism in Sr and Cs removal, rather than a Fe/Mn oxide dissolution mechanism.