Adsorptive removal of Pb(II) and Cd(II) ions from aqueous solution onto modified Hiswa iron-kaolin clay: Equilibrium and thermodynamic aspects

In view of promising adsorption efficiency of clay based materials, a modified iron-kaolin clay was used as an adsorbent of Pb(II) and Cd(II) ions from aqueous solutions. The effects of various experimental parameters, such as initial metal ions concentration, contact time, temperature and pH were investigated. The Langmuir and Freundlich adsorption isotherm models were applied to the experimental equilibrium data at different temperatures. The maximum adsorption capacities of Pb(II) and Cd(II) ions were 76.92 and 75.19 (mg/g), respectively. Thermodynamic parameters such as the change of Gibbs free energy, enthalpy and entropy of adsorption were also calculated and it was found that the lead and cadmium ions uptake by modified kaolin clay is endothermic and spontaneous in nature