Original scientific paper
Published in: Holistic Approach Environ. 3(2013) 3, pp. 116 – 133
Paper reference number: HAE-44
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UTILIZATION OF TUNISIAN BENTONITE AS ION-EXCHANGE AND SORBENT MATERIAL IN THE REMOVAL OF LEAD FROM AQUEOUS SOLUTIONS

Yasser Hannachi^*, Tarek Homri^*, Taoufik Boubaker^*

^* Faculty of Sciences of Monastir, Tunisia

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ABSTRACT

The adsorption characteristics of Pb(II) ions using the Tunisia  bentonite were investigated. Experimental parameters affecting the adsorption process such as pH, contact time, adsorbent dosage and temperature were studied. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were applied to describe the biosorption isotherms. The adsorption capacity of bentonite for Pb(II) ions was found to be 36.23 mg/g. From the D–R isotherm model, the mean free energy was calculated as 11 kJ/mol, indicating that the adsorption of Pb(II) ions was taken place by ion-exchange process. The calculated thermodynamic parameters showed that the adsorption of Pb(II) ions onto  bentonite was feasible, spontaneous and exothermic in nature. Kinetics data were best described by pseudo- second- order model. Infrared (IR) spectra of the bentonite sample showed that the positions and shapes of the fundamental vibrations of the OH and Si–O groups were influenced by the adsorbed Pb(II) cations. The X-ray diffraction (XRD) spectra indicated that the Pb(II) adsorption onto the bentonite samples led to changes in unit cell dimensions and symmetry of the parent bentonite.

Keywords: bentonite, ion-exchange, Langmuir isotherm, pseudo-second- order model, mass transfer analysis, thermodynamic, (IR) spectra, (XRD) spectra
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