Ion-exchange properties of the natural zeolite amicite

Crystals of the natural zeolite amicite, ideally K 4 Na 4 (Al 8 Si 8 O 32 )·10H 2 O, were ion-exchanged in the reactions with 0.1 N aqueous solutions of AgNO 3 , RbNO 3 , CsNO 3 and Pb(NO 3 ) 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 + ; Pb 2+ 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.