Ion-exchange properties of γ-zirconium phosphate.

g-Zirconium phosphate (g-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 Sr 2+ over g-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 g-ZrP following pseudo-second order kinetics with a much faster uptake of Rb + than of Sr 2+ . g-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 + , Mg 2+ , Ca 2+ , or transition metals such as Cu 2+ , Ni 2+ , Fe 2+ , Fe 3+ , Co 2+ and Zn 2+ . The used sorbent can be fully regenerated by nitric acid, enabling the recovery of Rb + .