In this study, three adsorbents were prepared with the raw kaolin issued from the Tamazert region in Algeria (Tamazert kaolin (KT)), for the removal of basic dye methylene blue (MB) from aqueous solutions. The first absorbent, KT-1, was obtained by thermal treatment; the second, KT-2, was obtained by thermal followed by acid treatment; and the third, KT-3, was obtained by thermal followed by acid and alkaline treatments. These adsorbents were characterized by powder X ray diffraction, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area, and scanning electron microscopy. Adsorption equilibrium isotherms of MB were correlated with common isotherm equations such as Langmuir and Freundlich models. The modified kaolins (KT-1, KT-2, and KT-3) showed different capacities of the equilibrium adsorption in comparison with raw kaolin (KT). The maximal adsorption capacity (111 mg g À1 ) was observed with modified kaolin (KT-3). The effect of operating parameters such as the initial dye concentration, contact time, adsorbent dose, pH, and temperature were studied onto KT-3. The removal of MB by adsorbent increased with an increase in adsorbent dose and initial concentration. Kinetics models, the pseudo-first-order, and pseudo-second-order rate equations were applied. The obtained results show that the adsorption of MB by KT-3 was well described by the pseudo-second-order kinetic model. The thermodynamic study revealed that the adsorption process was spontaneous, endothermic, and the positive value of ÁS indicated the affinity of MB molecules to the adsorbent surface. This study showed that this new adsorbent could be a good candidate for some activated carbons.

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An iron catalyst supported on the modified Tamazert kaolin has been prepared and tested in catalytic wet peroxide oxidation using phenol and 4-chlorophenol (4-CP) as target compounds (100 mg/L initial concentration). Kaolin is not usually employed as a catalytic support due to its low developed porous structure, but its textural properties may be improved upon calcination and acid and basic treatment. The catalyst was characterized by N2 adsorption–desorption and chemical analysis by total-reflection X-ray fluorescence spectroscopy. The catalytic tests were carried out in a batch reactor with a stoichiometric amount of H2O2. The catalytic efficiency was studied within the temperature range of 25–55°C at an initial pH of 3.3 and 1 g/L catalyst. Complete phenol and 4-CP removal was achieved with no significant differences in phenol and 4-CP conversions within the temperature range tested. Meanwhile, total organic carbon (TOC) reduction was greatly favoured by increasing the temperature, which may be partially attributed to a probable contribution of a homogeneous reaction associated with iron leaching. However, this effect might be of limited significance because the highest concentrations of iron in the liquid phase were below 4.5 and 8.5 mg/L in the experiments with phenol and 4-CP, respectively. At 55°C, TOC was reduced by ~70% after 4 h reaction time, with the remaining by-products corresponding almost completely to low-molecular-weight carboxylic acids of very low ecotoxicity.

In this investigation, Maghnia (Ma) and Mostaganem (Ms) bentonite clays, mined from west Algeria, with no prior affinity for anionic dyes, were modified by simple ion exchange with aqueous Fe3+ solutions, followed by calcination at 500°C. The resulting materials, Fe-Ma and Fe-Ms, respectively, were employed as adsorbents for methyl orange. The starting materials and the two adsorbents were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, Brunauer–Emmett–Teller specific surface area and X-ray fluorescence and by determining the point of zero charge. The effects of various variables, such as initial dye concentration, contact time, adsorbent dose, initial pH and adsorption temperature, were studied. The kinetics were well described by the pseudo-second-order model and the mechanism was determined from the intraparticle diffusion model, while corresponding isotherms fitted better to the Freundlich model. Thermodynamic parameters showed that the adsorption process was endothermic, spontaneous and physical in nature, accompanied by an increase of entropy.

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