Synthesis and characterization of zirconium and hafnium sulfates, hydroxide sulfates and oxide sulfates

Abstract

Reactions between ZrO2 or HfO2 and 50-95 wt% H2SO4 have been studied at temperatures up to the boiling point of the acid. Eight different solid products, depending on the H2SO4 concentration, were obtained, including new polymorphs of Zr(SO4)2·7H2O, Zr(SO4)2·4H2O and Hf(SO4)2·7H2O. In addition four solid intermediates were identified by thermal decomposition of Zr(SO4)2·4H2O and Hf(SO4)2·4H2O. Zirconium and hafnium hydroxide sulfates were prepared by slow evaporation of diluted aqueous solutions of zirconium and hafnium sulfates, respectively. On partial thermal decomposition of these, the corresponding oxide sulfates were obtained as intermediates. A simple procedure for disengagement of zirconium and hafnium sulfates from the concentrated H2SO4 mother liquor is described. TG and DTA data are presented, unit-cell dimensions are derived from PXD data and formulae based on TG analyses are given for the synthesized products. Copyright © Acta Chemica Scandinavica 1999.