Ion-exchange mechanism of some bivalent transition-metal ions on half-converted sodium and lithium forms of crystalline zirconium phosphate

Abstract

The ion-exchange processes of Ni²⁺, Co²⁺, Cu²⁺, Mn²⁺, and Zn²⁺ on half-converted sodium and lithium (M^I) forms of crystalline zirconium phosphate, ZrHM^I(PO₄)₂·nH₂O, occur in two steps from 0 to 80% and 80 to 100% conversion of the exchanger. Different ion-exchange mechanisms operate for the first step of exchange, depending on the proton activity in solution. Measurements on mixtures of transition-metal ions and fully converted metal(II) forms of zirconium phosphate, ZrM^II(PO₄)₂·nH₂O, show that the exchange is a non-equilibrium process.