<p>The development of efficient and sustainable adsorbents for heavy metal removal remains an important challenge in water remediation. In this study, a novel pyrazolone-functionalized “tweezer-like” biopolymer (AAF) was synthesized by modifying chitosan through a one-pot Mannich-type reaction using 4-aminoantipyrene and formaldehyde. The incorporation of pyrazolone groups introduces additional nitrogen and oxygen-donor sites and forms a cooperative binding architecture that enhances the affinity of the material toward Pb(II) ions compared with conventional chitosan-based adsorbents. The successful functionalization and physicochemical properties of AAF were confirmed through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, X-ray diffraction (XRD), ¹H-NMR and elemental analysis. The adsorption performance of AAF toward Pb(II) ions was systematically investigated through batch experiments under varying operational parameters. Under optimized conditions, the material exhibited excellent removal efficiency, achieving up to 98.98% Pb(II) elimination from aqueous solution. Process parameters were statistically optimized using Response Surface Methodology (RSM) combined with a Box–Behnken Design (BBD), and the developed model showed strong agreement with the experimental data. Adsorption equilibrium followed the Langmuir isotherm model with a maximum adsorption capacity of 59.17&#xa0;mg g⁻¹ at pH 6.0 and 298&#xa0;K. Kinetic studies indicated that the adsorption process follows a pseudo-second-order model, suggesting that chemisorption dominates Pb(II) binding. Furthermore, AAF exhibited good regeneration ability and maintained stable performance over six adsorption–desorption cycles using dilute HNO₃, demonstrating its potential as a cost-effective and environmentally sustainable adsorbent for practical Pb(II) remediation in contaminated water systems.</p>