Mechanistic Investigation of Visible-Light-Driven Photocatalysis in Bio-Synthesized Graphitic Carbon Nitride/MgO Nanocomposites Toward Safranine Orange Dye.

In this work, we report a sustainable strategy for the synthesis of magnesium oxide (MgO) nanoparticles, graphitic carbon nitride (g-C3N4), and MgO/g-C3N4 nanocomposites derived from orange peel waste, with MgO loadings ranging from 28 to 76 wt %. Comprehensive physicochemical characterization, including optical spectroscopy, structural analysis, and electron microscopy, confirmed the successful formation of well-dispersed heterostructures with tailored surface functionalities. The photocatalytic performance of the as-prepared materials was evaluated toward the degradation of Safranin O under simulated solar irradiation. Among all samples, the nanocomposite containing 61 wt % MgO exhibited the highest activity, achieving 89% degradation within 120 min. Kinetic investigations revealed a rate constant approximately 4.6 and 3.7 times higher than those of pristine g-C3N4 and MgO, respectively, highlighting the strong synergistic interaction between both components. Importantly, cytotoxicity assays conducted on human dental pulp stem cells demonstrated the good biocompatibility of the synthesized materials. Overall, this study presents a green and scalable route to engineer efficient and biocompatible photocatalysts from biowaste, offering promising prospects for sustainable water-remediation applications.