Removal of Pb⁺² Ions from Aqueous Solutions by Adsorption on Kaolinite Clay

The adsorption potential of the kaolinite clay for the removal of lead ions from aqueous solutions was tested. The measured adsorption isotherms at the different temperatures 298.15 K, 308.15 K and 318.15 K were found to be perfectly fit to the Langmuir isotherm equation. A high adsorption capacity was calculated. An increase in the retention capacity with increasing temperature was measured. The adsorption process was found to be endothermic with an estimated mean enthalpy change of 135.2 kJ/mol. The measured adsorption kinetic data at different temperatures proved that not only intraparticle diffusion controls the adsorption process but also surface adsorption contributes to the control of rate of adsorption. The influence of pH in the acidic range was investigated. The measured increase in the adsorption rate at higher pH values (4.9) was explained through the influence of H⁺ ions on the complex ion formation.