Ion exchange of K4Nb6O17·3H 2O

Abstract

Ion exchange of the layered compound K₄Nb₆O₁₇·3H₂O with mono- and bi-valent cations (Li⁺, Na⁺, Ca²⁺, and Ni²⁺) has been carried out in the aqueous chloride solutions at 90 °C. Only Na⁺ was found to attain to complete exchange. For exchange with Li⁺, almost all the K⁺ ions in the interlayers seemed to be replaced, although partial decomposition was observed. The degrees of exchange with the bivalent cations were found to be < 50%. The interlayer spacings of interlayers I (hydrated) and II (not hydrated) in K₄Nb₆O₁₇·nH₂O and derivatives were determined from electrondensity projections along the b axes. From the change in interlayer spacings, it is considered that K⁺ ions in interlayer II are only substituted by monovalent cations whereas both mono- and bi-valent cations exchange for K⁺ in interlayer I. By exchanging K⁺ in interlayer II with Li⁺ or Na⁺, this interlayer becomes hydrated.