Application of Isotherm and Kinetic Models for the Removal of Lead Ions from Aqueous Solutions

Abstract

The aims of the current study were to evaluate the ability of three types of Thai bentonite (TNBC) for the removal of lead ions [Pb(II)] from aqueous solutions. Batch-adsorption kinetic experiments revealed that the sorption of Pb(II) onto TNBCs was very fast and reached equilibrium after 30 min. The adsorption mechanisms in the Pb(II)/TNBC system follow pseudo–second order reactions. The adsorption isotherm of Pb(II) follows both Langmuir and Freundlich models. The maximum adsorption capacities for the three tested clays were 45.46, 40.00, and 47.62 mg/g, respectively. The results also revealed that the sorption energy (E-value) were 15.18, 11.85, and 17.25 kJ/mol, respectively, for the three tested clays. Desorption of Pb(II) ions and regeneration of the natural clays were attained simultaneously by acid elution. Even after four cycles of adsorption–elution, the adsorption capacity was maintained, and the decline in efficiency was less than 10%. It is concluded that Thai bentonite has an affinity to lead ions from aqueous solutions and might have a potential to be used effectively to remove Pb(II) wastewater.