Removal of Pb(II) from aqueous solutions by low cost adsorbent, Equilibrium, kinetic and thermodynamic studies

The ability of Moroccan clay, called locally Ghassoul, in removal of Pb(II) ions from aqueous solutions has been examined in a batch adsorption process with respect to several experimental conditions including pH, contact time, initial metal ions concentration, temperature, ionic strength. The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir, Freundlich and Dubinin–Radushkevich isotherms. The monolayer adsorption capacity was found as 90.91 mg g−¹. Kinetic studies revealed that Pb(II) ions uptake was fast with 90% or more of the adsorption occurring within first 30 min of contact time. The kinetic data fits to the pseudo-second-order model. Thermodynamic parameters including the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) changes indicated that the present adsorption process was feasible, spontaneous and endothermic in the temperature range of 25-45 °C.