Ion-exchange properties of the natural zeolite amicite

Abstract

Crystals of the natural zeolite amicite, ideally K4Na4(Al8Si8O32)·10H2O, were ion-exchanged in the reactions with 0.1 N aqueous solutions of AgNO3, RbNO3, CsNO3 and Pb(NO3)2 at 363 K for 24 h. Under these conditions, Cs+ substitutes K+ whereas the most part of Na+ remains unexchanged; Rb+ partly substitutes both Na+ and K+; Pb2+ and Ag+ completely substitute Na+ and K+. All the compounds are monoclinic. The Cs- and Rb-substituted samples have unit-cell parameters close to those of initial amicite. The exchange of Na+ and K+ for Ag+ is accompanied by a significant decrease of the unit-cell volume. The unit-cell parameter c of Pb-amicite is nearly threefold larger than the c parameter of initial amicite. Infrared spectra show that framework topology is preserved during the ion exchange. The crystal structures of initial and Cs-exchanged amicites have been solved by direct methods.