Green Synthesis of Zinc Oxide Using Oil Palm Leaf Extract for the Photocatalytic Degradation of Amoxicillin
摘要
Pharmaceutical waste is a growing environmental concern, particularly antibiotics, which can contaminate water systems and contribute to the development of resistant bacteria. In this study, we used zinc oxide prepared through a green synthesis method to photodegrade amoxicillin, one of the most widely used antibiotics worldwide. Oil palm leaf extract was utilized for the green synthesis of zinc oxide, thereby minimizing the use of toxic chemicals. Zinc oxide samples obtained with and without the addition of hydroxide showed good crystallinity but distinct morphologies. The alkaline medium increased the thermal stability of organic materials and favoured the obtention of particles with rod morphology. The characterization results from different techniques indicated the presence of well-structured carbonaceous materials with a high concentration of hydroxyl groups on the surface of the ZnO synthesized in an alkaline medium. This material has a band gap of 3.15 eV, which is narrower than the band gap of ZnO obtained by conventional methods. The photocatalytic assays demonstrated a degradation efficiency of up to 89% after 60 min and total degradation at 100 min of irradiation, with an apparent kinetic constant of 4.46 × 10–2 min−1 for the most active photocatalyst. The higher photocatalytic activity of the material prepared with oil palm leaf extract in alkaline medium can be attributed to the high concentration of hydroxyl groups in its composition. These hydroxyl groups are converted into hydroxyl radicals (·OH) with the photoexcitation of ZnO, resulting in a highly oxidizing medium. The plausible pathways of amoxicillin degradation were proposed based on LC–MS data, indicating that all products resulting from the β-lactam ring hydrolysis are ultimately degraded.
Graphical Abstract