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Tamazert kaolin was modified with dimethyl sulfoxide (DMSO). The starting material and resulting from the intercalation were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). Intercalation caused considerable changes in our clay by increasing the basal spacing to 11.22 Å, an intercalation rate of 98 %. The adsorption of methylene blue was studied as a function of pH, contact time, temperature, dye concentrations and adsorbents. Kinetic data have been adequately described by the pseudo-second order and intraparticle scattering model. The adsorption isotherm is in good agreement with the Redlich-Peterson model. A change in thermodynamic values (ΔH°, ΔS° and ΔG°) was observed after intercalation. Adsorption became non-spontaneous exothermic and ordered.

a b s t r a c tThe removal of cadmium(II) and lead(II) from aqueous solution was investigated using thermally processed halloysite. The samples were previously heated in the 200-1000°C range at interval of 200°C. The resulting materials were characterized by thermal analysis, electron microscopy, X-ray diffraction, electrophoretic mobility measurement, and N2 adsorption. Metal adsorption was studied as a function of pH, contact time, temperature, metal and adsorbent concentrations, and correlated with the physicochemical properties of the materials. A particular interest has been focused on the spectroscopic study to elucidate the mechanism of the interaction of M 2+ (M = Cd or Pb) cations with the best adsorbent. The kinetic and equilibrium data were adequately described by the pseudo-second order and Redlich-Peterson models, respectively. The mechanism mainly involved an electrostatic interaction between these metallic cations and the hydroxyl groups of surface. Whatever metal, maximum adsorption occurred for the material that preserved its structure, i.e. H200 (halloysite heated at 200°C) for Pb(II) and H400 for Cd(II). The intermediate adsorption of H600 and H800 was explained by their poorly organized structures due to dehydroxylation. H1000 was found to be the worst adsorbent due to its low specific surface area. Regardless of the material, the adsorption sequence was: Pb > Cd, which was correlated with the ionic properties of each metal. As long as it preserves its structure, halloysite clay proves to be an efficient adsorbent for removing heavy metals from aqueous solutions.

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