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ABSTRACT:The adsorption ability of natural clay towards the removal of basic dyes from aqueous textile solutions was investigated. The equilibrium isotherms were measured and analyzed using the Langmuir model and the experimental results compared with the theoretical data. The adsorbent exhibited considerable adsorption capacities of 567, 526, 427 and 300 mg/g towards Neutral Red, Methyl Violet, Methyl Green and Methylene Blue, respectively. Thus, the clay may be used as a cost-effective industrial adsorbent for the removal of basic dyes from industrial effluents.

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The removal of fluoride ions from an aqueous solution using a modified sulfuric acid clay was studied in batch adsorption. The adsorption kinetics were studied to identify the retention mechanisms. For kinetics study, perfectly stirred batch experiments were carried out after the adjustment of the parameters influencing the system, such as the pH, the adsorbent dosage, the initial concentration of fluoride ions, and the stirring speed. It appears that the rate of fluoride ion removal (1) increased with the mass of adsorbent and the stirring speed, and (2) decreased with the initial fluoride ion concentration. The experimental results were adjusted according to kinetic equations representing four external transport models. The latter were used to calculate the external mass transfer coefficient, k f . The results showed that this coefficient is in the range of 10 À5 e10 À4 m s À1 .