The Mossbauer spectroscopy and SEM investigation shows that crosslinked ionic polymers containing strongly basic functional groups adsorb Fe(III)-containing cations from sulphate solution through the formation in the polymer phase of high dispersed particles of jarosite mineral type compounds. Using different procedures the particles sizes and morphology, their repartition on the surface and in the volume of the polymer granule, the composition of the "polymer-inorganic compound" structural units were modified that is important for sorbents and catalysts obtaining. On heating in water medium in a boiling water bath, a part of the jarosite type compounds in the polymer phase is converted into ultra fine beta-FeOOH particles in superparamagnetic state and the rest, in relatively massive and magnetically ordered beta-FeOOH particles. The higher is the content of the Fe(III) in the polymer phase, the shorter is the duration of heating in water for the appearance of relatively massive particles of beta-FeOOH. The particles of the jarosite type compounds and of the beta-FeOOH are formed both on the surface and in the volume of the polymer granule. Upon heating in water, a part of the Fe(III)-containing particles have migrated from the volume of the polymer granule to the surface. Thermogravimetric investigation (in an N(2) atmosphere) shows that on heating of the Fe(III)-containing polymer sample up to 900 degrees C, complicated processes take place. (C) 2011 Elsevier B.V. All rights reserved.