Biosynthesis and response surface optimization of methyl violet 10B adsorption onto Moringa oleifera–mediated silver nanoparticles

The increasing global demand for sustainable wastewater treatment has intensified interest in developing cost-effective and environmentally benign nanomaterials. In this study, biogenic silver nanoparticles (MO/AgNPs) were synthesized using Moringa oleifera leaf extract as a natural reducing and stabilizing agent and first applied as a bioadsorbent for Methyl violet 10B removal from aqueous solutions. The MO/AgNPs were characterized before and after adsorption. Zeta potential shifted from − 24.5 mV to less negative after adsorption, indicating interactions between dye molecules and nanoparticles. X-ray diffraction confirmed their crystalline structure, while transmission electron microscopy revealed uniformly distributed spherical nanoparticles with diameters of 9.03–12.54 nm. A central composite design (CCD) was applied to evaluate and optimize the combined effects of solution pH, contact time, MO/AgNPs concentration, and initial dye concentration on dye removal efficiency. The experimental CCD runs showed removal efficiencies ranging from 41.29% to 90.73%, with the highest observed removal of 90.73% obtained at pH 11, contact time 90 min, MO/AgNPs concentration 1 mg/mL, and initial dye concentration 75 ppm. Desirability-based optimization then predicted a maximum Methyl violet 10B removal efficiency of 95.72% at pH 8.07, contact time 68.11 min, MO/AgNPs concentration 1.25 mg/mL, and initial dye concentration 67.98 ppm. Experimental validation under these conditions yielded a removal efficiency of 96.13%, closely agreeing with the predicted value and confirming the accuracy and reliability of the developed model. These findings demonstrate the novel application and considerable potential of M. oleifera -mediated silver nanoparticles as an efficient, eco-friendly, and sustainable adsorbent for treating dye-contaminated wastewater.