Nuclear magnetic resonance study of ion-exchange reaction on cubic ammonium molybdate

Abstract

Inorganic ion-exchangers generally exhibit high ion-exchange selectivity in comparison with organic ion-exchangers. The high selectivity has been ascribed to the rigid lattice of the crystal structure, e.g. ion-sieving properties of zeolites. Cubic ammonium molybdate prepared by the precipitation method (CAM) has been shown to have an unusual (compared with other inorganic ion-exchangers) selectivity for K⁺ among alkali-metal ions. The selectivity of K⁺ was assumed to result from the hydration of ions incorporated in the crystal lattice. The hydration property of alkali-metal ions incorporated in the lattice was revealed from the ¹H NMR study and the selectivity for K⁺ was accounted for by the hydration of K⁺ by analogy with the well known properties of electrolyte solutions.