Schinus molle extract mediated green synthesis of iron niobate photocatalyst for the degradation of methyl orange dye under visible light

FeNbO4 monoclinic nanocomposite semiconductors were synthesised using hydrothermal and sol gel methods; photocatalysts were then calcined at 800 °C. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy (UV/Vis) and X-ray diffraction (XRD) technologies were used to investigate crystallinity, morphology and optical properties of the photocatalysts. Fourier transform infrared spectroscopy (FTIR) was used to determine the functional groups of both treated and untreated FeNbO4. It was found that the S. molle extract-treated FeNbO4 prepared using the hydrothermal method (FeNbO4-HT + S. molle) has the smallest nanoparticles (22.8 nm) with the smallest band gap energy (2.78 eV). X-ray photoelectron spectroscopy verified the presence of the elements of FeNbO4 as well as their oxidation states. The photodegradation reactions of 10-ppm methyl orange dye solutions using FeNbO4-sol gel, FeNbO4-HT and FeNbO4-HT + S. molle were carried out under visible light (>420 nm) for 50 min. The reactions resulted in degradation percent of 74 %, 78 % and 96 % by using FeNbO4-sol gel, FeNbO4-HT and FeNbO4-HT + S. molle respectively. The photocatalytic activity of FeNbO4 treated with S. molle extract demonstrated superior light absorption and photostability, which is attributed to the consistency in the photocatalysts’ morphology, optical band gap, particle size distribution, and porosity. The photocatalysts remained stable and effective for five degradation cycles.