LAUSR

Abstract Large amounts of radioactive Sr produced in nuclear reactor need to be separated for alternate use or safe disposal. Herein effective separation of radioactive Sr2+ by crystalline complex phosphates, namely a tunnel structured K2Ce(PO4)2 (KCP) and a layer structured K2Zr(PO4)2 (KZP) is reported. These phosphates were prepared by high temperature solid state reaction method and characterized by X-ray diffraction using synchrotron X-ray sources. Ion exchange properties of these materials have been evaluated by using solutions of radioactive 85Sr. Both the materials show quantitative separation of Sr2+ but at different pH. Distribution constants (Kd) show increasing trend with increasing pH and show maximum values ∼ 8000 at pH 14 for KCP and ∼ 30,000 in neutral medium for KZP. The ion exchange capacities (qe) increase with increasing Sr2+ ions concentration and the typical values of qe are ∼ 521 μmol/g for KCP and ∼ 603 μmol/g for KZP. Correlation of structure and ion exchange properties indicated that the layered structure of KZP is the origin for its large Kd. The studies on kinetics and exchange isotherms of both KCP and KZP suggest for pseudo-second order favorable chemisorptions processes. From ex situ high temperature reactions, it is proposed that these lattices can be converted to stable apatite or NZP type matrices with the separated Sr2+ ions from the nuclear waste.