Novel alginate carbon nanoparticle composite beads for efficient removal of Pb2+ ions from aqueous solutions

Adsorption of lead is an environmentally sustainable approach to remediate lead pollution in water to protect human and environmental health. Therefore, the current study seeks to develop a new adsorbent material using alginate carbon nanoparticle (ACNP) composite beads and explore its efficacy in removing lead ions through a series of batch experiments. SEM and EDX analysis have been used to characterize ACNP composite. ACNP showed strong Pb 2+ adsorption at pH 5.5. The pseudo-first-order model cannot adequately fit the experimental data. The high R 2 (0.99) and strong agreement between the observed q e (13.81 mg/g) and computed q e (14.62 mg/g) values demonstrate the pseudo-second-order model's applicability to explain and interpret the experimental data. The intraparticle diffusion model had a low R 2 value, indicating that intraparticle diffusion was not the only rate-controlling step for the removal of Pb 2+ ions by the ACNP composite beads and chemisorption was involved in the adsorption process. The Langmuir model's strong correlation coefficient ( R 2 = 0.997) confirms monolayer coverage and chemisorption of Pb 2+ onto the adsorbent surface. The experimental findings demonstrated good compatibility for the Freundlich model, indicating chemical adsorption. The linear graph of the Temkin isotherm matches well, with R 2 of 0.97 confirming chemical adsorption. The DKR mean free energy, E = 13.3 kJ/mol, indicate chemisorption with ion-exchange mode. The values of Δ G ° indicate favorable adsorption at lower temperatures, whereas the value of Δ H ° (− 65.0 kJ mol −1 ) implies exothermic adsorption, as evidenced by decreased Pb 2+ adsorption as temperature rises. HCl solution can be used to regenerate ACNP composite beads. Therefore, the current work suggests that ACNP composite beads might be a suitable material for sequestering lead ions from aqueous solutions.