Adsorption of lead(II) onto magnetic chitosan@calcium phosphate rock biocomposite

A new magnetic chitosan@calcium phosphate rock (MCs@CPR) biocomposite was synthesized to be an efficient adsorbent for lead (II) adsorption from water. The composite was characterized by XRD, FTIR, SEM, XPS, BET, and point of zero charge (pH_PZC) analysis. Batch adsorption experiments were performed under various conditions including contact time, pH, initial Pb(II) concentration, adsorbent dose, and temperature. Equilibrium data were fitted to kinetic and isotherm models while theoretical calculations were performed to gain insight into adsorption mechanism. The pseudo-second-order model well represented the kinetic data, while the monolayer adsorption capacity was 234.19 mg g⁻¹ at 25 °C. The Pb(II) uptake process was spontaneous and endothermic. Theoretical calculations exhibited a good correlation between the simulated and the experimental data. Pb(II) adsorption involved electrostatic interaction, ion exchange, pore filling, surface complexation, van der Waals (vdW) interaction, and precipitation. The presence of co-existing ions reduced Pb(II) uptake capacity. The composite showed reusability capability up to four cycles. The composite can be a promising adsorbent to decontaminate other emerging contaminants from actual wastewater.