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Abstract
The ores of rare earth elements (REEs) are usually digested in concentrated sulfuric acid media, which dissolve the REEs as main product with heavy metals as byproduct. In the present work, inorganic ion exchangers based on silico-antimonates (SiSb) were synthesized and characterized. SiSb mixed with metal oxides were prepared in molar ratio 2:1 with different aging time. In batch experiments, radionuclides Eu-152 and Co-57 were taken to represent the lanthanides and heavy metals, respectively. The sorption behavior was examined and distribution coefficients were evaluated for different effective conditions such as sulfuric acid concentration, pH, shaking time, metal ion concentration, and aging time. The new inorganic SiSb materials are characterized by rapid kinetics for Eu(III) and high adsorption selectivity for Co(II). The results showed that the SiSb are acidic in character and that their cation-exchange properties are better in low acidic media. Sorption efficiency is highly correlated with the structural framework, which depends on exchangeable water content. Various chelating agents were tested for desorption of the retained Eu(III) and Co(II). Maximum separation factors were obtained with SiSb materials after 2 or 3 days aging, providing efficient exchangers for the separation of economically valuable REEs from heavy metals.