Zn-Ferrite and Hematite Dispersed by SBA-15 Silica Grains: Visible Light-Driven Photocatalytic Activity for Advanced Oxidation Process on Amoxicillin

Nanoparticles of ZnFe2O4 and hematite with varied sizes and distributions were synthesized using the two-solvent method (cyclohexane, water) on SBA-15 silica batches. Calcination is performed in air at 700 °C (2 °C/min) with rapid quenching produced catalysts with distinct nanoparticle configurations, namely, internal zinc ferrite and external hematite. The choice of precursor was critical, and nitrate salts yielded only zinc ferrite nanoparticles, while chloride salts produced a mixture of hematite and zinc ferrite. The photocatalytic activity of these materials was evaluated under visible light irradiation from an LED lamp, using O2 from air as an oxidizing agent without the addition of H2O2. Samples enriched with external hematite nanoparticles from chloride precursors achieved the highest activity, decomposing 30% of AMX in 225 min. In contrast, nitrate-derived samples with predominantly internal zinc ferrite nanoparticles exhibited lower catalytic activity. Characterization via TEM, XRD, N2 sorption, and Mössbauer spectroscopy confirmed the structural and magnetic properties of the nanoparticles. Mössbauer spectra, particularly at 12K and under a magnetic field, demonstrated the presence of hematite nanoparticles, distinguishing them from isolated Fe (III) cations. Zinc ferrite nanoparticles exhibited specific magnetic ordering, with Fe ions occupying tetrahedral and octahedral sites. The results demonstrate the critical role of nanoparticle, composition, and positioning in optimizing photocatalytic efficiency for water decomposition.