Umbite type zirconium germanates for Cs removal

Pure and Nb-doped zirconium germanate materials of composition K₂-xZr_1-xNb_xGe₃O₉.H₂O where x = 0, 0.1, 0.2 and 0.3 with the structure of the natural mineral umbite have been prepared in high yield using hydrothermal synthesis methods. The parent material displays virtually no ion exchange of the K⁺ for Cs⁺ but the doped materials show rapidly enhanced exchange with replacement of ca. 70% of the K⁺ by Cs⁺ for the 30% doped material. Rietveld analysis of the powder X-ray diffraction data is consistent with no change in the unit cell parameters or K⁺ bonding prior to the exchange, hence we propose the improved property is due to the creation of cation defect sites within the pores of the material that facilities greater cation mobility and leads to exchange.