Sorption of cesium radionuclides from aqueous solutions onto natural and modified aluminosilicates

Abstract

Sorption of ¹³⁷Сs from aqueous solutions onto natural aluminosilicates and onto those modified with mixed nickel potassium (NPF) and iron potassium (IPF) ferrocyanides was studied. The support being modified influences the composition, structure, and thermal stability of the formed ferrocyanide compounds and the sorption properties of the resulting sorbents. The modification increases the cesium distribution coefficients and static exchange capacity; it also extends the pH range of aluminosilicate operation. The most effective sorbents for cesium were obtained on the basis of glauconite (Gl) and clinoptilolite of the Shivertui deposit (ClSh). The cesium distribution coefficient on NPF-ClSh sorbent in the concentration range 10^–7–10^–5 mg L^–1 was logK _d [mL g^–1] = 7.0 ± 1.0, and on NPF-Gl and NPF-ClSh samples in the concentration range 10^–4–10² mg L^–1, logK _d [mL g^–1] = 5.0 ± 0.3 and 5.7 ± 0.4, respectively. The cesium uptake at concentrations in solution ≥100 mg L^–1 occurs owing to precipitation of mixed nickel cesium ferrocyanides in the pore space of the sorbents, which considerably enhances their capacity. The static exchange capacity for cesium of NPF-Gl was 220 ± 23, and that of NPF-ClSh, 500 ± 60 mg g^–1.