Synthesis and leachability studies of NZP and eulytine phases

Many Zr-containing phases of the sodium zirconium phosphate (NZP) type stru cture have been evaluated as host materials for the immobilization of radio nuclides. Phosphates crystallizing in eulytine type structure are identifie d as promising crystalline hosts matrices for the immobilization of rare ea rth cations and are tested for the first time. The soxhlet tests performed on these two kinds of phosphates with different crystal structure show that the Ln(3+) in eulytine and Zr4+ in the NZP phases show very low leach rate s of the order of 10(-5) to 10(-6) g m(2) day even in powdered samples. The leach rates attain levelling after 4-5 days. It is found that the leaching process is controlled by both diffusion and dissolution. The leaching proc ess of the individual species is found to depend on the charge density of t he respective ions present in the matrix. (C) 1998 Elsevier Science Ltd. Al l rights reserved.