Comparative Study of the Extraction of Cu(II) and Fe(II) Ions Using Chitosan and Modified Chitosan/Polyvinylpyrrolidone Adsorptive Membranes: Adsorption, Kinetic, and Thermodynamic Study

Abstract

The current work examined chitosan's adsorption capabilities for removing Cu(II) and Fe(II) ions from the aqueous phase in a batch equilibrium system. The membranes were prepared using the leaching-out method. The effects of the adsorbent's initial pH, concentration, temperature, and dose on adsorption were examined. Adsorption tests were conducted at temperatures ranging from 15 to 45 °C and initial concentration ranges of 20−400 mg/L. The observations from the adsorption isotherms fitted the Langmuir and Freundlich model adequately. The nonlinear form of the pseudo-first-order model was followed by the kinetics of Cu(II) and Fe(II) on chitosan, and the model parameters were reliably obtained. The endothermic and spontaneous character of Cu(II) and Fe(II) adsorption on chitosan adsorbents was verified by the computed negative values of standard Gibbs free energy and positive enthalpy changes. Finally, chitosan (CS) showed to be an efficient adsorbent for the removal of Cu(II) and Fe(II) ions due to its high adsorption capacity for Cu(II), which was 182.15 mg/g for C1, 331.28 mg/g for C2, and 384.31 mg/g for C3, and Fe(II), which was 201.67 mg/g for C1, 352.53 mg/g for C2, and 315.8 mg/g for C3 (where C1 is the CS membrane, C2 is the CS/silica membrane, and C3 is the CS/polyvinylpyrrolidone membrane).