Adsorption of lead (II) and chromium (VI) onto activated carbon prepared from pineapple peel: Kinetics and thermodynamic study

Abstract

The locally available adsorbent pine apple peel (Ananascosmosus) has been tested by preparing activated carbon by KOH activation for its effectiveness in removing hexavalent chromium and divalent lead present in the water at low concentrations. Batch adsorption method has been employed to investigate the efficiency of the adsorbent. Adsorption parameters like adsorbent dose, pH, contact time and temperature have been obtained. Adsorption isotherms Freundlich and Langmuir, which states that heterogeneity of the adsorbent surface, were tested and the data obtained best fits to Freundlich model. The adsorption kinetics follow pseudo-second-order kinetic model. Thermodynamic parameters for Pb (II) and Cr (VI) adsorption, enthalpy change, (-0.149 and -0.081kJ/mol), entropy change (0.183 and 0.012kJ/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 show that adsorption is feasible, spontaneous in nature, and exothermic.