NiO‐Decorated Activated Carbon for Selective and High‐Performance Pb(II) Adsorption

ABSTRACT Lead contamination in water systems poses a serious environmental and public health concern, necessitating the development of efficient and selective adsorbents. In this study, a NiO‐decorated activated carbon (NiO@AC) nanocomposite was synthesized via chemical activation followed by a precipitation‐assisted method. The resulting material exhibited well‐dispersed NiO nanoparticles on a porous carbon matrix. The adsorption performance toward Pb(II) ions was strongly dependent on solution conditions, with optimal removal achieved at pH 5. The NiO@AC nanocomposite demonstrated a maximum removal efficiency of 95% and maintained 89% removal at an initial Pb(II) concentration of 200 mg/L. Equilibrium data were best described by the Langmuir isotherm model ( R 2 = 0.9786), indicating monolayer adsorption with a maximum adsorption capacity of 826.9 mg/g. Kinetic analysis showed that the adsorption process followed the pseudo‐second‐order model, suggesting that both physical and chemisorption are the dominant mechanism. Furthermore, the nanocomposite exhibited strong selectivity toward Pb(II) ions in the presence of competing metal ions and retained good performance over repeated adsorption–desorption cycles, confirming its stability and reusability. These results highlight NiO@AC as an efficient, selective, and sustainable adsorbent with strong potential for practical wastewater treatment applications.