Sorption of Pb(II), Cd(II) and Zn(II) ions from aqueous solution using Jordanian kaolinite modified by the amino acids methionine or cysteine

Modification of kaolinite clay with amino acids methionine or cysteine and the adsorption of Pb(II), Cd(II) and Zn(II) ions from aqueous solutions were studied. The modified kaolinite (K-Meth or K-Cyst) was characterized by FTIR, TGA, SEM, and XRD. The sorption behavior and adsorption isotherms of the K-Meth or K-Cyst toward Pb(II), Cd(II), and Zn(II) was studied by batch equilibrium technique as a function of K-Meth or K-Cyst mass, pH, temperature and contact time. The column experiment was effectively used for the determination of metal ions loading capacity as well as for desorption studies. The K-Meth or K-Cyst showed high metal-ion uptake capacity towards Pb(II) more than Cd(II) and Zn(II). The adsorption isotherm data shows fittings for Langmuir's more than Freundlich and Dubinin-Radushkevich equations. The adsorption reaction was found to have positive values for H and S, this suggest an increase in randomness at the solid-liquid interface during the adsorption process. The interactions are thermodynamically favorable and are accompanied by a decrease in Gibbs energy with temperature. The column loaded K-Meth or K-Cyst was regenerated by 0.1 M HNO 3 and therefore can be employed for the removal of heavy metal pollutants in environmental and industrial applications.