Layered Double Hydroxide Adsorption of Lead: Equilibrium, Thermodynamic and Kinetic Studies

Layered double hydroxide (LDH) with Mg/Al ratio of 4:1 was synthesis by co-precipitation method and characterized for batch adsorption studies. Pre and post EDX analysis shows binding on the surface confirming adsorption. Kinetic modeling of the metal ion removal was done using First-Order and Pseudo second order models rate expressions respectively. Equilibrium isotherm data analysis for the metal ion was done with the Langmuir and Freundlich equations. Both the Langmuir adsorption isotherm (R=0.9993) and Freundlich adsorption isotherm (R0.9998) described the adsorption data very well. Thermodynamic parameters such as enthalpy (∆H◦), entropy (∆S◦), Gibbs free energy (∆G◦), activation energy (Ea) and isosteric heat of adsorption were calculated and the results are discussed in detail.