Solid-phase extraction of Cu²⁺ and Pb²⁺ from waters using new thermally treated chitosan/polyacrylamide thin films; adsorption kinetics and thermodynamics

<p>New biologically safe thin adsorptive films were synthesised using chitosan/polyacrylamide polymer blend (Ch/PA) via thermal crosslinking technique for the separation of Cu²⁺ and Pb²⁺ from aqueous solution and natural water samples. The prepared films were characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and Thermogravimetric analysis (TGA) techniques. Thermo-gravimetric analysis revealed an enhancement in the thermal stability of the prepared thin films with increasing polyacrylamide content. Kinetic and thermodynamic studies were evaluated by batch-type experiments. The obtained results indicated that the adsorption isotherms were well described by Freundlich model, and Ch/PA have adsorption capacities of 177.9 and 126.58 mg.g⁻¹ to Cu²⁺ and Pb²⁺, respectively. Under optimum conditions, calculated detection limits were as low as 0.018 and 0.034 μg.L⁻¹ for Cu²⁺ and Pb²⁺, respectively, and relative standard deviations of less than 4% for five separate experiments. Moreover, the traditional <i>Lagergren</i> adsorption kinetic model provided the best fitting for the kinetic data. Furthermore, the reusability studies revealed a decrease in the adsorption capacity by about 8% after three adsorption–desorption cycles. The prepared thin films were successfully applied for the separation of Cu²⁺ and Pb²⁺ from natural water samples.</p