Removal of lead ions by Unye (Turkey) bentonite in iron and magnesium oxide-coated forms

This paper presents the adsorption of Pb(II) from aqueous solution onto Unye (Turkey) bentonite in raw (RB), iron oxide-coated (ICB) and magnesium oxide-coated (MCB) forms. Adsorption of Pb(II) by samples was investigated as a function of the initial Pb(II) concentration, solution pH, ionic strength, temperature and inorganic ligand effect (Cl−). Changes in the surface and structure were characterized by means of XRD and N2 gas adsorption data. The Langmuir monolayer adsorption capacities of RB, ICB and MCB in 0.1 M KNO3 solution were estimated as 16.70, 22.20 and 31.86 mg/g, respectively. The spontaneity of the adsorption process is established by decrease in ΔG which varied from −21.60 to −28.60 kJ/mol (RB), −21.74 to −32.22 kJ/mol (ICB) and −26.27 to −33.11 (MCB) in temperature range 303-338 K.