Investigating the comparative adsorption of methyl orange and methyl green on commercial bentonite

This paper presents the utilization of commercial bentonite obtained from Biochem Chemopharma Company, in France, as an adsorbent for the anionic dye methyl orange (MO) and cationic dye methyl green (MG) in aqueous solutions. The material was analyzed using X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Nitrogen adsorption at 77 K and thermogravimetric analysis (TGA) were performed for characterization. The study evaluated the impact of various experimental parameters such as contact time, solution pH, adsorbent dose, initial dye concentration, and temperature. Batch adsorption studies revealed that MO exhibited a maximum of 90 mg/g in an acidic medium, with an equilibrium time of 20 min and an adsorbent dosage of 1 g/L. On the other hand, MG demonstrated maximum adsorption of 165 mg/g in a natural medium, with an equilibrium time of 5 minutes and an adsorbent dose of 0.6 g/L. The adsorption of MO followed a pseudo-first-order kinetic model and the isotherms were well-fitted by the Freundlich model for MO and both Freundlich and Langmuir models for MG. Thermodynamic analysis indicated an exothermic, spontaneous, and physical adsorption process. Lastly, the adsorption performance of commercial bentonite for MO was compared with that of MG. Bull. Chem. Soc. Ethiop. 2025, 39(4), 643-657. DOI: https://dx.doi.org/10.4314/bcse.v39i4.4