Adsorption of trace elements or radionuclides on hydrous iron oxides

Factors that influence the adsorption of trace elements or radionuclides on hydrous iron oxides were investigated. The adsorption of monovalent cations (Cs⁺, Rb⁺) on hydrous iron oxides is not strongly pH-dependent and it can be regarded as nonspecific. On the other hand, the adsorption of Ag⁺, divalent cations (Zn²⁺, Cd²⁺, Mn²⁺, Sr²⁺) or trivalent cations (Cr³⁺, La³⁺, Ce³⁺, Eu³⁺, Gd³⁺, Er³⁺, Yb³⁺) is strongly pH-dependent. The regularities of the adsorption of these cations on hydrous iron oxides are discussed. Also, the differences in the adsorption behaviour of some divalent and trivalent cations are explained. Freshly precipitated iron(III) hydroxide can be used for the decontamination of radionuclides from low-level waste solutions. However, the efficacy of decontamination depends on the oxidation state and the chemical properties of radionuclides.