Synergistic Optimization of Pb(II) Adsorption from Aqueous Solutions by Manganese-Doped Carbon Aerogels

In this study, a novel carbon aerogel adsorbent (Mn-PA-CS) was synthesized through a one-step calcination-activation method using manganese acetate as the precursor. Unlike conventional phytic acid-activated carbons, this work introduces manganese doping as an effective strategy to tailor the pore structure and surface chemistry. The resulting material features enriched surface P/O functional groups and a significantly increased proportion of micropores (0.7–0.8   nm), which closely match the hydration diameter of Pb(II) ions, alongside elevated defect density (ID/IG = 0.94). These modifications synergistically promote adsorption through micropore filling, electrostatic attraction, and surface complexation. The optimized Mn-PA-CS, prepared with 100   mg of manganese acetate, exhibited a high Pb(II) uptake capacity of 302.88   mg·g -1 , which represents a 132.43% improvement compared to the undoped material. The adsorption behavior followed pseudo-second-order kinetics and the Freundlich isotherm, suggesting a spontaneous, endothermic, and multilayer chemisorption process. This study indicates that transition metal doping is a promising strategy for regulating the adsorption performance of bio-derived carbon materials.