State of iron in nanoparticles prepared by impregnation of silica gel and aluminum oxide with FeSO$_4$ solutions

The state of iron in nanoparticles prepared by impregnating silica gel and aluminum oxide with iron(II) sulfate solutions has been investigated using Mössbauer spectroscopy. It has been revealed that the state of iron depends on the nature of the support. Iron(III) hydroxysulfate and iron(III) oxysulfate nanoparticles are formed on the surface of silica gel, and iron oxide nanoparticles are formed on the surface of aluminum oxide. An increase in the concentration of iron ions or in the size of iron-containing particles leads to hydration of the nanoparticle surface. The calcination of the samples results in the formation of $\varepsilon$-Fe$_2$O$_3$ oxide in a strongly disordered or amorphous state in iron-containing particles on the surface of silica gel.