Effect of Particle Size on the Adsorption Behavior of Methylene Blue onto Activated Carbon

• Smaller activated carbon particles significantly enhance methylene blue adsorption capacity due to increased surface area and pore accessibility. • Adsorption kinetics follow a pseudo-second-order model, indicating chemisorption as the rate-limiting step. • Langmuir isotherm best fits equilibrium data, suggesting monolayer adsorption on a homogeneous surface. • Thermodynamic analysis reveals spontaneous and exothermic adsorption, favoring lower temperatures for efficient dye removal.