Síntese verde de ZnO puro e compósito magnético com Fe₃O₄ usando extrato da folha do dendezeiro para remediação fotocatalítica de norfloxacino

Abstract

A primary global concern in recent decades has been the improper disposal of pharmaceutical drugs due to their interaction with the ecosystem. Therefore, it is necessary to develop materials and processes that can degrade these pollutants, thereby minimizing environmental impacts. Advanced oxidation processes are considered promising alternatives, such as photocatalysis employing metal oxides, like ZnO, as photocatalysts. Among the methods for synthesizing zinc oxide, green synthesis is considered less environmentally harmful. It produces economic and ecological materials that minimize the use of toxic chemicals and energy consumption. In this work, zinc oxides, with and without iron, were prepared through green synthesis using oil palm leaf extract for application in the photocatalytic degradation of the aqueous antibiotic norfloxacin. The results indicate that phytochemicals from the oil palm leaf extract act as directing agents in the formation of hexagonal pyramids and bipyramids of ZnO, depending on the synthesis conditions and the zinc precursor. The materials in question were characterized by TG/DTA, XRD, FTIR, RAMAN, DRS, SEM, EDX, BET, and pHZPC. The results show that ZnO in the wurtzite phase is obtained under different conditions and, in the presence of iron, forms the magnetic composite ZnO/Fe3O4. All materials presented a band gap below 3.0 eV, and the results of photocatalytic tests indicate that pure zinc oxide prepared with zinc nitrate without pH adjustment had the best photoactivity, with approximately 86% of the antibiotic degraded in only 60 minutes of irradiation. The results also indicate that the degradation mechanism of norfloxacin shows a significant contribution from photogenerated holes (h+), followed by •OH radicals. The insertion of iron resulted in the formation of a ZnO/Fe3O4 magnetic composite, with magnetite nanoparticles dispersed within the hexagonal ZnO pyramids. Light absorption in the visible range is enhanced by the presence of Fe3O4 nanoparticles, as is the photocatalytic activity, resulting in 90% degradation of the antibiotic within 60 minutes of irradiation. In this case, •OH radicals contributed more significantly to the degradation of norfloxacin than the photogenerated holes (h+).