Comparative phenomenological modeling of the overall adsorption rate of drugs onto activated carbon. The case of the chlorpheniramine

Abstract

The adsorption of chlorpheniramine on a predominantly acid-granular activated carbon was studied using diffusional kinetic models. The experiments were performed on rotatory basket batch adsorbers at pH values of 4, 7 and 9 and temperatures of 25, 35 and 45 °C using the equilibrium concentration and uptake of each experiment to describe the equilibrium behavior. The textural characterization demonstrated a type IV N2 isotherm, indicating that the active carbon used combines micro and mesopores. The adsorption isotherms obtained presented Langmuir behavior with an average deviation of 3%. The diffusional modelling revealed that surface diffusion is the predominant intraparticle diffusion mechanism governing the adsorption process, with contributions to the total intraparticle diffusion being higher than 96% regardless of the radial position. However, these contributions decreased as low as 50% when Chlorpheniramine (CPM) uptake increased. The pH studies demonstrated that the surface diffusion coefficient increased as the pH increased due to a combination of stronger π stacking interactions and electrostatic interactions. Meanwhile the temperature study demonstrated an increase in surface diffusivity as the temperature increased due to the higher energy that the chlorpheniramine molecules gained due to the temperature increment.