Sustainable synthesis of iron-doped manganese oxide nanoparticles for effective photo-accelerated detoxification of tetracycline

The widespread use of antibiotics has severely impacted water bodies and ecosystems, necessitating well-designed photocatalysts for effective degradation. In this regard, present work reports the synthesis of MnO₂:xFe³⁺ (MF-x, x = 0, 2, 4, 6, 8, and 10) nanoparticles via the bio-mediated process using Tridax procumbens as the reducing and stabilizing agents. Various physicochemical approaches confirmed the structural, optical, and morphological properties of MF-x nanoparticles, revealing a reduced optical bandgap (2.06-0.97 eV) for visible-light photocatalysis. PXRD analysis reveals cubic crystalline nature of MF-x nanoparticles belonging to space group number 206 (I a-3) with crystallite sizes ranging 39-70 nm, which was further refined using Rietveld method with acceptable χ² value of 2.3 for the doped sample. Raman spectra confirmed the existence of F_g and E_g + F_g active modes from the bixbyite structure corresponding to the space group I a-3. Furthermore, the FESEM and TEM analyses showed a highly crystalline uniform porous morphology with evaluated particle sizes in agreement with the PXRD results. Additionally, the quantitative aspects of precursor elements were confirmed through XPS studies. The photocatalytic activity of MF-10 in degrading Tetracycline hydrochloride (TC-HCl) was evaluated under optimized pH, catalyst dosage, and TC-HCl concentration under visible light. Results show that optimized weight (100 mg) of as-synthesized nanoparticles exhibit high photocatalytic performance with a 94.23% degradation against optimized 20 ppm TC-HCl in 90 min. On the other hand, pH variation and reusability test indicated that the degradation efficiency was significant at neutral pH and reduced at the 5th cycle (64.28) which was further authenticated by pH_PZC evaluation (7.55). Thus, the present work showcased the potential application of MnO₂: Fe³⁺ nanoparticles as low-cost and environmentally friendly material in water treatment applications.