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<p>The sustainable green synthesis of MnO<sub>2</sub> nanoparticles (NPs) was optimized using response surface methodology (RSM) based on a central composite design (CCD). The developed quadratic model was highly significant (F = 21.28, <i>p</i> &lt; 0.0001) with strong predictability (R<sup>2</sup> = 0.9551). The optimized synthesis conditions for the reproducible formation of MnO<sub>2</sub> NPs were identified as 20&#xa0;g precursor, 500&#xa0;mL extract, 75&#xa0;°C, and pH 6. The synthesized NPs displayed characteristic absorption maxima at 266&#xa0;nm and were phase-pure α-MnO<sub>2</sub> with a tetragonal structure, nanoscale size (7–8&#xa0;nm), and defect-rich crystalline nature. Surface characterization proved good colloidal stability (− 28.8&#xa0;mV) along with the presence of phytochemical-derived functional groups, indicating effective bio-reduction and capping. Under the optimized conditions, the synthesized MnO<sub>2</sub> NPs displayed excellent efficiency for the removal of 4-Chlorophenol (98.47%) and Bisphenol A (97.61%). RSM analysis proved that the adsorbent dosage and contact time were the dominant factors for the removal of pollutants. Kinetic studies proved that the removal of pollutants followed a pseudo-second-order model and proved the involvement of chemisorption in the removal process. Isotherm and thermodynamic analyses revealed favorable, spontaneous, and endothermic adsorption, with a higher affinity toward 4CP. The high qmax values of 16.26&#xa0;mg g<sup>-1</sup> for 4CP and 11.93&#xa0;mg g<sup>-1</sup> for BPA indicate the superior adsorption capacity of MnO<sub>2</sub> NPs. Mechanistic investigations using HPLC, LC–MS/MS, and FT-IR proved a synergistic adsorption–oxidation pathway with the involvement of reactive oxygen species (ROS), leads to progressive degradation into low-molecular-weight intermediates. The nanoparticles retain &gt; 90% removal efficiency after five reuse cycles, indicates good stability and reusability. Overall, this study demonstrates a green and scalable synthesis approach for MnO₂ NPs with dual adsorption–catalytic functionality, offering an effective strategy for the removal of phenolic contaminants from aqueous systems.</p>

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Integrated response surface methodology for the optimization of green-synthesized MnO2 nanoparticles and their application in phenolic pollutant removal

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  • 发表日期：

    2026年7月24日

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  • Pavani Peddi

摘要

The sustainable green synthesis of MnO2 nanoparticles (NPs) was optimized using response surface methodology (RSM) based on a central composite design (CCD). The developed quadratic model was highly significant (F = 21.28, p < 0.0001) with strong predictability (R2 = 0.9551). The optimized synthesis conditions for the reproducible formation of MnO2 NPs were identified as 20 g precursor, 500 mL extract, 75 °C, and pH 6. The synthesized NPs displayed characteristic absorption maxima at 266 nm and were phase-pure α-MnO2 with a tetragonal structure, nanoscale size (7–8 nm), and defect-rich crystalline nature. Surface characterization proved good colloidal stability (− 28.8 mV) along with the presence of phytochemical-derived functional groups, indicating effective bio-reduction and capping. Under the optimized conditions, the synthesized MnO2 NPs displayed excellent efficiency for the removal of 4-Chlorophenol (98.47%) and Bisphenol A (97.61%). RSM analysis proved that the adsorbent dosage and contact time were the dominant factors for the removal of pollutants. Kinetic studies proved that the removal of pollutants followed a pseudo-second-order model and proved the involvement of chemisorption in the removal process. Isotherm and thermodynamic analyses revealed favorable, spontaneous, and endothermic adsorption, with a higher affinity toward 4CP. The high qmax values of 16.26 mg g-1 for 4CP and 11.93 mg g-1 for BPA indicate the superior adsorption capacity of MnO2 NPs. Mechanistic investigations using HPLC, LC–MS/MS, and FT-IR proved a synergistic adsorption–oxidation pathway with the involvement of reactive oxygen species (ROS), leads to progressive degradation into low-molecular-weight intermediates. The nanoparticles retain > 90% removal efficiency after five reuse cycles, indicates good stability and reusability. Overall, this study demonstrates a green and scalable synthesis approach for MnO₂ NPs with dual adsorption–catalytic functionality, offering an effective strategy for the removal of phenolic contaminants from aqueous systems.