Synthesis and Characterization of Protonated Zirconium Trisilicate and Its Exchange Phases with Strontium

A partially protonated form of the mineral umbite has been prepared by ion exchange of K2ZrSi3O9·H2O with acetic acid. The protonated phase, compound 1, is assigned the formula H1.45K0.55ZrSi3O9·2H2O and crystallizes in the space group P21/c with unit cell dimensions of a = 7.1002(2), b = 10.1163(3), c = 13.1742(5), and β = 91.181(1)°. The characteristic building blocks of the acid phase are almost identical to those of the parent compound. The framework is composed of polymeric chains of trisilicate groups linked by zirconium atoms, resulting in zeolite-type channels. When viewed down the a axis, two unique ion-exchange channels can be seen. Site 1 is marked by a 12-membered ring and contains 2 cations. Site 2, a 16-membered ring, contains 4 water molecules. Compound 2, consists of a mixed Sr2+ and K+ phase synthesized from 1 by ion exchange with Sr(NO3)2. Compound 2 has the formula K0.34Sr0.83ZrSi3O9·1.8H2O and crystallizes in the same space group P21/c. It has cell dimensions of a = 7.1386(3), b = 10.2...