| Summary: | Heterogeneous photocatalysis with TiO2 has shown high efficiency in the removal of a wide range of organic contaminants. Recently, significant efforts have been made to activate TiO2 under visible light wavelengths, and promising results were obtained by doping it with nitrogen. The main drawback of the use of nanoparticles for the purification of wastewater is their separation after the depollution treatment and this is an issue that has to be addressed for a proficient application of N-doped TiO2 nanoparticles. The use of magnetic core Fe3O4 and N-doped TiO2 shell nanoparticles could be a solution to this problem. With the aid of an external magnetic field, the removal and recycling of the photocatalyst nanoparticles become possible. For this reason, the aim of this work was to obtain nanocomposites consisting of visible active N-doped TiO2 supported on SiO2/Fe3O4 ferromagnetic nanoparticles. The nanocomposites were then evaluated in the photocatalytic removal of phenol. The photocatalytic tests were carried out in a recirculating batch cylindrical photoreactor irradiated by a strip of white LEDs surrounding the external surface of the reactor and emitting in the visible region.
The experimental results showed that N-doped TiO2/SiO2/Fe3O4 nanoparticles are effective in the removal of phenol, reaching degradation and TOC removal of about 64 and 55%, respectively, after an irradiation time of 270 min. The catalyst was collected at the photoreactor bottom after each test cycle by applying a magnet on the external surface of the photoreactor, so easily separating the treated solution from the photocatalyst. After washing with distilled water and drying at 50 °C, the photocatalyst was reused without further treatment. Photocatalytic tests on the recycled catalyst showed that N-doped TiO2/SiO2/Fe3O4 remains stable, evidencing phenol degradation in the range 59-65% after four operation/regeneration cycles.
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