Low leachability phosphate lattices for fixation of select metal ions

The feasibility of using phosphate compounds to fix ions of different sizes and charge such as Sr2+ Ba2+, Pb2+, Fe3+, Cr3+, Zr4+, Sm3+, EU3+, and Gd3 is investigated. Two structure types of phosphate compounds, viz., NZP (Na Zr2P3O12) and eulytine, are considered. The compounds of formula AM(3+)ZrP( 3)O(12) (A = Sr, Ba, and Ph; M3+ = Cr and Fe) [NZP] are studied with respec t to the incorporation of ions such as Fe3+, Cr3+, and Zr4+. The compounds of the formula M(3)LnP(3)O(12) (M = Sr and Ba; Ln = Sm, Eu, and Gd) [eulyti ne] are studied with respect to the encapsulation of rare earth ions. Chemi cal durability tests indicate that the leach rates of various ions from the NZP structure type compounds are of the order of 10(-4) gm(-2)d(-1), and o f the order of 10(-3) gm(-2)d(-1) from compounds with eulytine structure. ( C) 2000 Elsevier Science Ltd. All rights reserved.