Evaluation of Adsorption Capacity of Montmorillonite and Aluminium-pillared Clay for Pb2+, Cu2+ and Zn2+

Adsorption capacity of the two adsorbents was investigated as a function of contact time between adsorbent and heavy metal ions solutions, the initial heavy metals concentration of the synthetic wastewater, pH value, 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 (q(max) = 92.59 mg . g(-1)), 6.0 for lead (q(max) = 97.08 mg . g(-1)) and 6.5 for zinc ions (q(max) = 73.52 mg . g(-1)), respectively. The sorption capacity of studied adsorbents for Pb2+, Cu2+ and Zn2+ was calculated using Langmuir and Freundlich models. Thermodynamic parameters - enthalpy change (Delta H-0), entropy change (Delta S-0) and free energy (Delta G(0)) - 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. EDS characterization confirmed qualitatively the presence of adsorbed species in the samples. On the basis of the obtained results the adsorption it was proposed an ordered adsorption: Pb2+, Cu2+ and Zn2+, on the sorbents we investigated.