Joint synthesis of Fe₂O₃-SnO₂ nanostructured composite by the polyol method and its photocatalytic performance in rhodamine-B bleaching

ABSTRACT

Composites formed from semiconductor oxides have been synthesized and assessed for their properties and applications, as well as a photocatalyst for restoring aquifers through the degradation or bleaching of organic dyes. The Fe₂O₃-SnO₂ nanocomposite was prepared by the Polyol method, a technique not found for this composite so far in the literature, under reflux in ethylene glycol. The composite and the isolated oxides were synthesized by the same process, characterized, and evaluated as photocatalysts of Rhodamine-B in aqueous solution (10 mg.L^⁻1). The materials collected after the reflux performed at time intervals of 1 h and 8 h generated Fe₂O₃ and SnO₂, respectively, were analyzed by TGA/DTA and by XRD. It was found that α-Fe₂O₃ was obtained at 400 °C and SnO₂ at 650 °C. This composite was treated at 700 °C for 1 h. The SEM proved the formation of a nanostructured composite with SnO₂ nanoparticles. The BET curves indicated non-porous materials with surface areas of 18, 45 and 20 m².g^⁻1 for the samples prepared from Fe₂O₃, SnO₂ and the composite, respectively. The band gaps estimated at 1.9 eV, 3.5 eV and 1.8 eV, in the same sequence as above. The bleaching tests of Rhodamine-B, pH 5.5 in exposure to visible and ultraviolet light, showed completely different properties. The Fe₂O₃ particles showed physical adsorption capable of reducing light absorption by 75% in the initial 15 minutes, however, there was no bleaching over the next 75 minutes. The presence of SnO₂ in the solution showed a maximum bleaching of 45% after 120 minutes. The discoloration obtained by the nanocomposite in 180 minutes was 20%, a result attributed to the total covering of the surface of the α-Fe₂O₃ particles by the SnO₂ nanoparticles, preventing both the physical adsorption of the dye onto the iron oxide and the progress of the absorption mechanism. light followed by dye degradation.

Keywords
Nanocomposites; Polyol; Photocatalysis