Neem mediated silver nanoparticles for reactive orange dye adsorption with statistical optimization and artificial neural network modeling

The uncontrolled discharge of synthetic dyes into aquatic systems poses serious environmental and health hazards to humans and animals. Therefore, green, reusable, and effective adsorbents must be developed for sustainable treatment. This study investigated biosynthesized AgNPs as an adsorbent for RO dye removal. To confirm their crystalline structures, functional biomolecules, and surface morphologies, the nanoparticles were analyzed using XRD, FTIR, and FESEM-EDS. Batch experiments showed that dye removal was strongly affected by operational parameters. The maximum dye removal efficiency of 97% was achieved at a pH of 3, 70 °C, 2.5 g/L adsorbent dosage, and 60 min contact time. Kinetic and isotherm studies indicated that adsorption proceeded through a heterogeneous multistep process influenced by diffusion and surface interactions. Equilibrium data were fitted best with the Dubinin–Radushkevich and Temkin isotherms, indicating favorable adsorption on a heterogeneous surface. The ΔH° and ΔS° values were 79.57 kJ mol ⁻¹ and 247.4 J mol⁻¹ K⁻¹, respectively, confirming that the process was endothermic and spontaneous. The regeneration study demonstrated stable adsorption efficiency over five cycles, followed by gradual decline. RSM identified the optimum operating conditions for RO removal as 2.5 g L⁻¹ AgNPs dosage, pH ≈ 3, at 70 °C for 60 min, and ANN modeling showed strong predictive performance for the nonlinear adsorption behavior with temperature showing greater influence on adsorption behavior. Overall, neem-mediated AgNPs appear to be an eco-friendly, efficient, and reusable adsorbent for RO dye removal and may support sustainable water remediation applications.