Adsorption mechanisms of methylene blue and methyl orange on activated carbon: scientific interpretation and modeling simulation

Activated carbon was produced from olive waste to investigate the adsorption behavior of methylene blue (MB) and methyl orange (MO) dyes in aqueous solutions. The adsorbent was characterized using X-ray diffraction and scanning electron microscopy, and adsorption isotherms were measured at three different temperatures. A statistical physics framework was employed to analyze the adsorption mechanisms of the dyes on the carbon surface. The steric, energetic, and thermodynamic characteristics of the most relevant advanced were analyzed in detail. The number of active sites for MB was determined to range from 1.32 to 1.78, while for MO it ranged from 1.23 to 1.62, indicating that the orientation of dye molecules on the adsorbent is influenced by temperature. Overall, MB shows a slightly higher adsorption capacity than MO. Moreover, increasing the temperature reduces adsorption, indicating that the process is exothermic for both dyes. Moreover, adsorption energy values ranging from 9.85 to 18.90 kJ/mol indicate that physical interactions are responsible for the adsorption process. Thermodynamic characteristics demonstrated that deyes adsorption onto the AC adsorbent is spontaneous and feasible.