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+ .