New heavy metal-hydro-sodalites containing Cd2+, Ag+ or Pb2+: synthesis by ion-exchange and characterisation

The ion-exchange of the sodium-hydro-sodalites [Na4(OH)(H2O)]2[Al3Si3O12]2, [Na4(OH)]2[Al3Si3O12]2, [Na3(H2O)4]2[Al3Si3O12]2 have been studied in a variety of solutions. The synthesis parameters were determined for the three sodium-hydro-sodalites with Cd2+, Cu2+, Zn2+, Ag+ and Pb2+. The ion-exchange with silver, lead, and cadmium cations was found to yield pure sodalite phases, whereas with copper and zinc cations no pure sodalite phases were obtained due to Cu(OH)2 and Zn(OH)2 precipitation upon or within the sodalites. The new sodalite phases were characterised by X-ray powder diffraction, thermogravimetry, IR-, 1H-MAS NMR-, and X-ray absorption spectroscopy.