Ion-exchange Properties of γ-Zirconium Phosphate

γ-Zirconium phosphate (γ-ZrP) has potential as a very useful inorganic ion-exchanger due to its stability under thermal and acidic conditions. We recently reported its facile synthesis using a modified solventless method, which could make the exploitation of its ion-exchange properties for cleanup of radioactive materials and extraction of valuable ions feasible. The adsorption isotherms of Rb⁺ and Sr²⁺ over γ-ZrP are described well with the Langmuir model, with maximum adsorption capacity of 1.52 and 1.31 mmol/g, respectively. Both ions adsorb on γ-ZrP following pseudo-second order kinetics with a much faster uptake of Rb⁺ than of Sr²⁺ . γ-Zirconium phosphate shows very high affinity for Rb⁺ , allowing its enrichment from low-concentration solutions. Notably, Rb⁺ is selectively removed from complex solutions containing large amounts of Na⁺ , Mg²⁺ , Ca²⁺ , or transition metals such as Cu²⁺ , Ni²⁺ , Fe²⁺ , Fe³⁺ , Co²⁺ and Zn²⁺ . The used sorbent can be fully regenerated by nitric acid, enabling the recovery of Rb⁺ .