Alkali-metal ion exchange on acid tantalum phosphate

Exchange of protons for alkali-metal ions on acid tantalum phosphate, H5O2T a(PO4)(2), was studied, and the interdiffusion coefficients in the resultin g solid solutions were evaluated. The mobility of alkali-metal cations was found to decrease in the order DK+ > DLi+ similar or equal to DNa+ much gre ater than DCs+. An additional energy barrier for the transport of cesium io ns from the solution to H5O2Ta(PO4)(2) Was revealed. In the initial stages of exchange, the selectivity of the material studied for alkali-metal catio ns increases in the order Cs+ < K+ < Na+ < Li+ at room temperature and in t he order Cs+ < Na+ < Li+ < K+ at 313 K. At increased degrees of substitutio n, the material shows selectivity for sodium ions. The results are interpre ted in terms of the structure of solid solutions.