Kinetic and thermodynamic study of the adsorption of Pb (II) from aqueous solution to the natural and treated bentonite

Abstract

Lead (Pb) is one of the major environmental pollutants. Adsorption appears to be the most widely used for the removal of heavy metals. The aim of this work is to investigate the adsorption potential of commercial natural bentonite (NB) in the removal of Pb (II) ions from aqueous solution. The effect of different variables, such as, concentration of Pb, mass of NB, pH, time, NB washing and heat treatment and temperature was investigated. The bentonite sample under the heat and washed treatment are labeled as CB and WB respectively. The adsorption experiments were carried out using batch process. The equilibrium time for Pb (II) adsorption on NB was 5 min, the processes conforming to second order kinetics. NB had a much higher adsorption capacity for Pb (II) with the Langmuir monolayer capacity (qm) of 107, 110 and 120 mg g− 1 at 293, 313 and 333 K respectively compared to others adsorbents. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were calculated. The adsorption process was found to be endothermic and spontaneous. The enthalpy change for Pb (II) by NB adsorption has been estimated as 33 kJ mol−1, indicating that the adsorption of Pb (II) by NB corresponds to a physical reaction. The adsorption capacity of washed bentonite WB was very high compared to NB and CB   Key word: Adsorption, clay minerals, bentonite, lead, wastewater treatment