Evaluation of adsorption capacity of montmorillonite-K10 and Al-pillared clay towards Pb2+, Cu2+ and Zn2+ ions

Abstract

Adsorption capacity of the two adsorbents was investigated as a function of contact time, the initial heavy metals concentration of the synthetic wastewater, pH, temperature and adsorbent mass. Preliminary experiments at different pH values between 2.0 and 7.0 were performed and were observed that maximum adsorption occurs at pH 5 for copper, 6.0 for lead and 6.5 for zinc ions. Capacity of studied adsorbents for adsorption of Pb²⁺, Cu²⁺ and Zn²⁺ was calculated using Langmuir and Freundlich models. Thermodynamic parameters - enthalpy change (ΔH⁰), entropy change (ΔS⁰) and free energy (ΔG⁰) - were calculated for predicting the nature of adsorption. Scanning electron micrograph (SEM) revealed changes in the surface morphology of the adsorbent as a result of heavy metal ions adsorption. On the basis of obtained results it was proposed an order of adsorption of  Pb²⁺, Cu²⁺ and Zn²⁺ on sorbents.