Adsorption Behavior of Beryllium(II) on Copper-oxide Nanoparticles Dispersed in Water: A Model for ⁷Be Colloid Formation in the Cooling Water for Electromagnets at High-energy Accelerator Facilities

Abstract

The adsorption behavior of Be(II) on CuO nanoparticles dispersed in water was studied as a model for colloid formation of radioactive ⁷Be nuclides in the cooling water used for electromagnets at high-energy proton accelerator facilities. An aqueous Be(II) solution and commercially available CuO nanoparticles were mixed, and the adsorption of Be(II) on CuO was quantitatively examined. From a detailed analysis of the adsorption data measured as a function of the pH, it was confirmed that Be(II) is adsorbed on the CuO nanoparticles by complex formation with the hydroxyl groups on the CuO surface (>S–OH) according to the following equation:
n > S–OH + Be²⁺ ⇔ (>S–O)_n Be⁽²⁻ⁿ⁾⁺ + nH⁺ (n = 2, 3) S : solid surface.
The surface-complexation constants corresponding to the above equilibrium, β_(s,2) and β_(s,3), were determined for four types of CuO nanoparticles. The β_(s,2) value was almost independent of the type of nanoparticle, whereas the β_(s,3) values varied with the particle size. These complexation constants successfully explain ⁷Be colloid formation in the cooling water used for electromagnets at the 12-GeV proton accelerator facility.