Bioinspired Synthesis of Propolis-Capped Silver Nanoparticles for Rapid Azo Dye Adsorption: Experimental Performance, Thermodynamic Evaluation, Regeneration, and Computational Insights

The development of sustainable nanomaterials is essential for efficient wastewater treatment. This study evaluates silver nanoparticles (AgNPs), synthesized through an ecofriendly green route using Algerian propolis extract, as reusable nanoadsorbents for the rapid removal of Basic Blue 41 (BB41) from aqueous solutions. AgNPs were characterized before and after adsorption using UV–Vis, XRD, FTIR, SEM/EDS, and XPS. Adsorption performance was tested alongside thermodynamic, regeneration, and density functional theory (DFT) analyses. Characterization confirmed the face-centered cubic structure of metallic silver and dye uptake via propolis-derived surface functional groups. The AgNPs showed exceptionally rapid adsorption within 8 min. The process was spontaneous and exothermic, following the Langmuir model from which a maximum adsorption capacity (qmax) of 754.96 mg g−1 was derived. For the regeneration tests over six adsorption–desorption cycles, the adsorption efficiency decreased from 94.55% in the first cycle to 29.37% in the sixth cycle. DFT analysis revealed a favorable BB41–Ag66 interaction within the adopted finite-cluster model, with a BSSE-corrected interaction energy of −4.085 eV, consistent with contributions from interfacial polarization and dispersion. Ultimately, these findings highlight Algerian propolis-mediated AgNPs as fast-acting, high-capacity nanoadsorbents for dye removal, supported by solid experimental and computational mechanistic insights.