Kinetic, isotherm and thermodynamic study of methyl orange adsorption on raw clay from north of Morocco

Clay and clays minerals have highly reactive surface and interesting texture properties that can easily remove organic and inorganic contaminants from wastewaters.  In this perspective, this work reports the study of clay-pollutant interactions by using Moroccan clay as absorbents and methyl orange as anionic model of dyes textile. The clay was sampled in the region of Tetouan. Structural and physicochemical properties of the sample were determined   by different characterization techniques (XRD, IR, FTIR, SEM, ATG/ADT, BET, and CEC). The results reveal that the raw clay is mainly composed of kaolinite and smectite as clay minerals. The SiO2 / Al2O3 ratio is about 2.4. Its CEC is about 25.34 meq/100g. The specific surface area is about 51.28 m2/g. The adsorption isotherms were carried out using batch conditions. The kinetics adsorption of MO on the clay revealed that equilibrium is rapidly   reached. The data were adjusted by four kinetic models: pseudo-first-order, pseudo-second-order, intra-particle diffusion model and Elovich model. The pseudo second-order model was the most adequate to describe the adsorption kinetics of the MO dye. The experimental results were modeled by four models, namely Langmuir, Freundlich, Dubinin Redushkevich (D-R) and Elovich. The adsorption isotherm shows that the Langmuir model perfectly represents the adsorption of methyl orange on the studied clay. The adsorption capacity is high and reach 113 mg/g. The thermodynamic parameters obtained indicate that the adsorption of methyl orange is feasible and spontaneous. The obtained results showed clearly the selected clay could be used as adsorbent of anionic dyes.