Core–shell type magnetic Ni/NiO nanoparticles as recyclable adsorbent for Pb (II) and Cd (II) ions: One-pot synthesis, adsorption performance, and mechanism.

Abstract A polymer-assisted one-pot synthesis of Ni/NiO core-shell type nanomaterial and the assessment of Ni/NiO as a potential adsorbent for heavy metal removal has been reported. The controlled synthesis process enables the formation of nanoparticle with magnetic properties, which facilitates separating the nanoparticles easily from aqueous media in the presence of an external magnet. The formation of the Ni/NiO nanostructure was confirmed through structural and spectroscopic characterizations. The experimental results suggested that the adsorption capacities of Ni/NiO were ∼308 mg g−1 and ∼172 mg g−1 for Pb (II) and Cd (II) ions, respectively. Time-dependent adsorption studies indicated that the adsorption of heavy metal ions on Ni/NiO is primarily dominated by film diffusion and follows a pseudo-second-order kinetics equation. The equilibrium experiment results suggested that heavy metal ion adsorption on Ni/NiO is a physical adsorption process and follows the Langmuir isotherm model. The thermodynamic parameters (ΔH and ΔG) computed from the temperature-dependent adsorption experiments indicated endothermicity spontaneity of the adsorption process.