Synthesis and investigation of the kinetics of ion exchange in solid solutions of substitution of Н$^{+}$/Ме$^{+}$ (Ме=Na$^{+}$, K$^{+}$) antimony and phosphorous antimony acids

The kinetics of ion exchange in antimony acid (SC) of the composition H$_2$Sb$_2$O$_6\cdot$nH$_2$O, where $2<n<5$, and phosphorous antimony acid (FSK) of the composition H$_2$Sb$_{13/7}$P$_{1/7}$O$_6\cdot$nH$_2$O, where $2<n<4$, crystallizing in the structural type of pyrochlore (etc. gr. simm. Fd3m). It is shown that sodium and potassium ions replace oxonium ions (protons) and are located in the channels of the crystal structure of SC and FGC (16d positions). Ion exchange models are considered and it is shown that film kinetics is realized at the initial stages of substitution, and subsequently the Boyd model in the approximation of the spherical grain model describes the processes of ion exchange. The mechanisms of substitution of proton groups in SC and FGC are clarified and the coefficients of mutual diffusion are calculated.