Fabrication of Pinus pinaster’s Tannin-Engineered Silver Nanophotocatalyst for Degradation of Methylene Blue Dye

The increasing demand for sustainable nanomaterials has driven the development of green synthesis strategies that replace conventional toxic reagents with renewable bioresources. Plant-derived phytochemicals provide an eco-friendly pathway for fabricating functional nanoparticles for environmental applications. Therefore, in this study, silver nanoparticles (AgNPs) were synthesized via a green approach using tannins extracted from Pinus pinaster as natural reducing and stabilizing agents, thereby eliminating the need for hazardous chemicals. The formation of Pinus pinaster’s tannin mediated AgNPs (PPT-AgNPs) was confirmed through UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), and transmission electron microscopy (TEM). The microscopy studies revealed that AgNPs particle sizes ranged from 15.9 to 96.4 nm. The photocatalytic activity of the synthesized AgNPs was evaluated for the degradation of methylene blue dye under UV irradiation. The photocatalytic reaction deviates from classical Arrhenius kinetics but may be governed by a balance between molecular kinetics, adsorption/desorption equilibrium and/or charge carrier recombination rates. Optimum conditions were achieved at pH 5 and 30°C, reaching a degradation efficiency of 87.37% within 5 h. Kinetic analysis showed that the degradation followed pseudo-first-order kinetics with a rate constant of 0.4961 h⁻¹. Overall, the utilization of Pinus pinaster tannins as natural reducing and stabilizing agents provides a sustainable route for AgNP fabrication, yielding photocatalysts with promising activity for wastewater treatment applications.