Ion-exchange and protonic species in the antimony hydrogen phosphate HSb(PO4)2·2H2O

Abstract

It has been established from the incoherent inelastic neutron scattering spectra (IINS) that both the oxonium [H3O]+ and dioxonium [H5O2]+ ions are present in the antimony hydrogen phosphate H1Sb(PO4)2·2H2O, written as H1SbP2·2H2O. However, as the extent of hydration decreases as in H1SbP2·1.25H2O, the proportion of the oxonium [H3O]+ ion increases. MAS NMR indicates that the P—O–H+ group remains undissociated in the anhydrous form. The title compound is an efficient but unselective ion exchanger which is able to extract mono- and poly-valent aquo-cations. In addition, polyvalent complex cations may be exchanged directly without the need for a catalytic or delamination process. A relatively high temperature (266 °C) is needed to dehydrate Co[Sb(PO4)2]2·6H2O in which the cobalt appears to be bound to four water molecules with two axial oxygens from the macroanionic layers.