Removal of Pb ions using green Co₃O₄ nanoparticles: Simulation, modeling, adsorption, and biological studies

Chemical co-precipitation synthesized novel and green cobalt-oxide nanoparticles (Co₃O₄-NPs) utilizing cobalt nitrate as cobalt precursors. FTIR, Raman, scanning electron microscopy, UV visible, X-ray powder diffraction, and BET was used to analyze the surface characteristics, composition, and morphology, of the NPs. These green Co₃O₄-NPs were employed to remove Pb ions from simulated wastewater solutions at various pH, adsorbate, temperature, and dose concentrations. At dose 20 mg/L, pH 6.0, 20 mg/L (Pb(II) solution, 25 °C of temperature, and 45 min for equilibrium, nearly 99.44% of Pb ions were removed. To evaluate the kinetic data, four different kinetic equations were used. The data fit the Elovich rate equation better than the other three models. Thermodynamic and isothermal studies were also evaluated, and the maximum adsorption capacity of 450.45 mg/g was observed at 298.15 K. 0.1 M HNO_3, and 0.1 HCl were used to regenerate used Co₃O₄-NPs. Simulation results show the strong correlation of the Co atom in the Co₃O₄-NPs generates active delocalized surface states, which are energetically most favorable for heavy metal (Pb ions) adsorption and removal, supporting the experimental outcomes. In concluding remarks, green Co₃O₄-NPs can also be used as an adsorbent to remove Pb ions from wastewater bodies.