In this study, the adsorption of an industrial dye Supranol Yellow 4GL onto Cetyltrimethylammoniumbentonite (CTAB-bentonite) is investigated. The organobentonite is synthesised by exchanging cetyltrimethylammonium cations (CTAB) with inorganic ions on the surface of bentonite. The adsorption of Supranol Yellow 4GL onto organobentonite is found to be maximum when the concentration of CTAB exchanged is 100% according to the cation exchange capacity of the clay (CEC). The modification of organobentonite is examined using XRD and FTIR techniques.The effect of the process parameters such as: contact time, adsorbate concentration, adsorbent dose, pH and temperature are reported. Nearly 1200 seconds of contact time are found to be sufficient for the adsorption to reach equilibrium. The pseudo second order model is used to describe the kinetic data, and the rate constant is therefore evaluated. The dye adsorption to organobentonite is characterized by monolayer isotherm and caused by adsorption with relatively strong uptake. The Langmuir and Freundlich models adsorption are applied to describe the isotherm equilibrium and to determine its constants. The Langmuir and Freundlich models agree well with the experimental data with a adsorption capacity of 0.5 g of dye per g of organobentonite. A better fixation was obtained at acidic pH. The effect of temperature on the adsorption of dye has been also studied and the thermodynamic parameters H , S, G, Abbreviations C i the initial concentration of dye, g/L C e the concentration of dye in solution after equilibrium, g/L V the total volume of the solution, L m the mass of the adsorbent, g q e the amounts of dye adsorbed at equilibrium time, g/g q the amounts of dye adsorbed at time t, g/g K 1 the pseudo-first order rate constant, sec −1 K 2 the pseudo-second order rate constant, sec −1 q m the amount of solute adsorbed per weight of adsorbent in forming a complete monolayer on the surface, g/g bLangmuir constant related to the energy, L/g R L dimensionless separation factor k and n Freundlich constants k d the partition coefficient, L/g

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