Efficient removal of Pb(II) and Zn(II) ions from aqueous solutions by adsorption onto a native natural bentonite

The new Native Natural Bentonite (NNB) for adsorption of Pb(II) and Zn(II) ions from aqueous environments was investigated at 27 ± 1⁰C by in batch laboratory experiments. Chemical and mineralogical structure of the NNB adsorbent was characterized by XRF and cation exchange capacity (CEC). The effect of pH, metals concentration, adsorbent dose, and agitation time were also studied. Langmuir and Freundlich isotherm and the Giles classification isotherm were used for describing the equilibrium data. The results show that the NNB contains silica (SiO₂) and alumina (Al₂O₃) as a major chemical compound. The maximum adsorption capacity (mg/g), based on Langmuir isotherm were 8.55 and 7.90 for Pb(II) and Zn(II), respectively. Pb(II) and Zn(II) removal efficiency was increasing by increasing the initial pH of solutions, adsorbent dose, and contact time. Therefore, the results of this study show that the equilibrium is reached slowly (180 min), indicating the adsorption sites are not well exposed. By increasing the initial metals ion concentration, the capacity of adsorption decreased and the uptake of Pb(II) and Zn(II) per unit weight of the adsorbent (mg/g) increased. The adsorption efficiency of Pb(II) was higher than Zn(II).