Sorption of actinide ions onto mesoporous phosphorus-containing silicas

Abstract

Equilibrium and kinetic characteristics of template mesoporous silicas containing phosphonic acid residues in sorption of various actinide ions were studied. The sorption equilibrium involving these sorbents is attained within 20 min after introducing the sorbent into the solution. The calculated values of the internal diffusion coefficient $(\bar D)$ and half-exchange time (τ_0.5) in sorption of uranium were ∼3.5 × 10⁻¹⁶ m² s⁻¹ and ∼390 s, respectively. Mesoporous phosphorus-containing silicas efficiently sorb from acid solutions uranyl ions, Th(IV), and Pu(IV). In sorption of uranium from sulfuric acid solutions, the capacity of the sorbents is 125–132 mg g⁻¹, and in sorption from nitric acid solutions (0.5–3.0 M HNO₃), 276–299 mg g⁻¹. In sorption of Th(IV) from nitric acid solutions, the capacity of the sorbents is 60–66 mg g⁻¹. In sorption of microamounts of ²³⁹Pu(IV), the distribution coefficient reaches 4500 cm³ g⁻¹. Phosphorus-containing silicas in nitric acid solutions do not noticeably sorb ²⁴¹Am, which allows using them for efficient separation of the Pu/Am pair with the separation factor of no less than 2 × 10₃.