Hydrogel template-assisted synthesis of nanometric Fe2O3 supported on exfoliated clay

• Clay mineral/poly(acrylic acid) hydrogel nanocomposite was synthesized.
• Structural analysis confirmed intercalation of the polymer into the clay gallery.
• High adsorption capacity of Fe3+ ions for the studied nanocomposite was observed.
• Clay/hydrogel composite was modified with controlled amounts of Fe.
• Calcined materials exhibited very high dispersion of Fe2O3 nanoparticles.

A synthesis of metal oxide modified clays based on the hydrogel template assisted route was proposed. This novel method was verified by an intercalation of poly(acrylic acid) (PAA) into the interlayer space of montmorillonite (MT) using the in situ polymerization technique. The obtained hydrogel/clay composite with a MT/PAA mass ratio close to 1.0 exhibited an expanded layered structure and an excellent adsorption capacity for transition metal cations. These features were exploited to the modification of MT-PAA material with various amounts of Fe3+ cations by deposition at controlled pH = 2.5. The introduced Fe species favored the hydrogel burning, therefore in a subsequent step the organic template could be easily removed by calcination under oxidizing conditions at temperature protecting the clay against deep dehydroxylation. A gradual delamination of MT with an increase in the Fe content was observed after thermal treatment. This effect resulted in opening of the MT structure, manifested by a relatively high surface area and a large porosity. XRD, TEM, UV–Vis-DRS and XPS measurements exhibited that the formed α-Fe2O3 nanoparticles were highly dispersed on the exfoliated clay, which comprised a framework stabilizing the nanophase.

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