Abstract

Radioactive trace ⁷Be produced in cooling water systems for high-energy accelerators is known to be captured by metal-oxide colloidal nanoparticles generated through corrosion of metal components in water. This study is aimed at investigating the adsorption behavior of trace Be²⁺ onto various oxide nanoparticles (Al₂O₃, SiO₂, TiO₂, Fe₂O₃, CoO, and CuO) dispersed in water at 25 °C in order to clarify the tendency and features of the interaction of Be²⁺ with metal oxides. From pH dependence of the distribution ratio of Be²⁺ between the nanoparticle phase and the aqueous solution phase, the surface complexation constants (β_s,n) have been determined for the reaction of Be²⁺ with the hydroxyl groups on the oxide surface (>S−OH), i.e., Be²⁺ + n >S−OH ⇄ (>S−O)_nBe⁽²⁻ⁿ⁾⁺ + n H⁺. The n values are generally 1 and 2 and the sequences of the β_s,n values are Fe₂O₃ > TiO₂ » Al₂O₃ > SiO₂ for β_s,1 and Fe₂O₃ > TiO₂ > SiO₂ > Al₂O₃ >> CoO » CuO for β_s,2. The dependences of the the β_s,n values on the kind of oxide are explained based on the electronegativity of the metal (or Si) composing the oxide.

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