Abstract

The Sm and Ag doped SrTiO3 nanoparticles have been effectively produced by using a sol-gel method with citric acid acting as a chelating agent in the ethylene glycol solution for the efficient photodegradation of methylene blue dye under visible light irradiation. All samples show evidence of the creation of the cubic perovskite structure according to X-ray diffraction (XRD) analysis. Images captured by field emission scanning electron microscopy (FESEM) have verified that the addition of doping elements has reduced the particle size and ensured consistency in the samples. The produced samples' UV-vis spectra show a blue-shift in the absorption tail as well as a decrease in band gap energies of 3.61 eV, 3.56 eV, and 3.53 eV with SrTiO3, Sm@SrTiO3, and Sm@Ag@SrTiO3. The ideal photocatalyst operating conditions were determined to be 5 ppm of initial Methylene Blue (MB) concentration, 0.005 g/L of catalyst dosage, and 100 min of irradiation time. Additionally, the photocatalytic analysis shows that the doped sample has a higher rate of MB degradation under visible light. Sm@Ag@SrTiO3 nanoparticles exhibit 80 % higher photocatalytic activity compared to Sm@SrTiO3 and SrTiO3, which have efficiencies of 50.88 % and 30.23 %, respectively. The trans-esterification process was optimized using a 4:1 alcohol-to-oil molar ratio, 100 mg of Sm@Ag@SrTiO3 NPs catalyst, a 60-min reaction time, and 80 degrees C temperature, achieving a biodiesel yield of up to 85 %. The catalyst maintained high efficiency over multiple runs, demonstrating consistent performance and stability. These findings emphasize the catalyst's potential for cost-effective and sustainable biodiesel production.