Kinetic and Thermodynamic Study of the Adsorption of Methyl Red by Natural and Modified Clays from Côte d’Ivoire

Agri-food and textile industrial units located near waterways discharge their wastewater, which often contains large quantities of toxic dyes, potentially carcinogenic and very dangerous for humans. It is necessary to effectively treat these industrial effluents in order to limit their impact on the environment. Thus, the treatment of colored solutions has become one of the interests of scientific research. It is in this context that this work examines the ability of clays to remove the methyl red contained in aqueous solutions. For this, clays from Côte d’Ivoire were brought into contact with synthetic solutions of methyl red by following parameters such as contact time, pH of the medium (2-10), temperature (293 K – 323 K), mass of clay (5 mg – 80 mg) and initial concentration of methyl red (5 mg/L – 100 mg/L). Experiments have shown that the adsorption capacity increases quickly during the first 30 minutes of contact. The contact time for reach equilibrium can be estimated as 30 minutes. The adsorption reaction is described by a second-order kinetic model. It is influenced by the pH of the medium, the temperature and the valence of the saturating cation and its degree of hydration. The adsorption capacity increases with the mass of clay, the initial concentration of methyl red, the content of iron compound, of titanium oxide TiO2 and the importance of the clay fraction with a diameter < 2 μm. Thermodynamic parameters revealed that it is a spontaneous physical adsorption.