Adsorption of Lead (II) and Chromium (VI) onto Activated Carbon Prepared from Pineapple Peel: Kinetics and Thermodynamic Study

In this study, locally available adsorbent pineapple (Ananas comosus) peel has been tested by preparing activated carbon through KOH activation for its effectiveness in removing hexavalent chromium and divalent lead present in water at low concentrations. A batch adsorption method was employed to investigate the efficiency of the adsorbent. Adsorption parameters such as adsorbent dose, pH, contact time, and temperature were studied. The adsorption isotherms of Freundlich and Langmuir were tested, indicating the heterogeneity of the adsorbent surface, with data best fitting the Freundlich model. The adsorption kinetics followed a pseudo-second-order kinetic model. Thermodynamic parameters for Pb (II) and Cr (VI) adsorption, including enthalpy change (-0.149 and -0.081 kJ/mol), entropy change (0.183 and 0.012 kJ/mol), and Gibbs free energy change (-3.138 and -3.554 kJ/mol at 293 K, -3.191 and -3.615 kJ/mol at 298 K, -3.245 and -3.675 kJ/mol at 303 K), respectively, have been calculated. The results indicated that the adsorption process was feasible, spontaneous, and exothermic.