Investigation of kinetics, thermodynamics, and isotherms of the simultaneous removal of heavy metal ions by activated carbon from cypress fruit

Abstract

This research investigates the simultaneous removal of lead ion-Pb(II), cadmium ion-Cd(II), and cobalt ion-Co(II) from aqueous solution and real samples using activated carbon (AC-C) synthesized from cypress fruit. The investigation meticulously examines the prompt of several adsorption parameters (pH, adsorbent dosage, temperature, initial concentration, and agitation time) on the effectiveness of heavy metal removal by AC-C. FTIR, SEM, and EDS analyses provide convincing evidence for the effective adsorption of metal ions onto the AC-C surface. Pb(II) performed best at a concentration of 40 mg.L −1 in an acidic solution (pH 5) with 70 mg of adsorbent and 100 min of agitation time. Co(II) and Cd(II) achieved their highest removal rates at a concentration of 90 mg.L −1 in basic solutions (pH 10) with 70 mg of adsorbent and 90 min of agitation time. Under these optimal conditions, AC-C demonstrates remarkable removal efficiencies of 98.68% for Pb(II), 95.60% for Co(II), and 76.45% for Cd(II). Kinetic studies reveal that the adsorption process fits a second-order model for the simultaneous removal of the three metal ions. Additionally, equilibrium data are best characterized by the Langmuir isotherm model, indicating monolayer adsorption of the heavy metal ions mixture. Thermodynamic analysis provides further insights into the adsorption process. The positive enthalpy (ΔH°) confirms the endothermic adsorption of the three ions, and the positive entropy (ΔS°) predicts an unpredictable nature at the solid-solution interface. This study establishes AC-C derived from cypress fruit as a highly effective and promising candidate for the simultaneous removal of Pb(II), Cd(II), and Co(II) from aqueous environments. Its remarkable performance, coupled with the readily available natural resource, paves the way for wider application of AC-C in environmental remediation strategies.