Adsorption equilibrium and kinetics of pharmaceutical compounds onto granular activated carbon from aqueous phase

The aim of this study was to investigate the adsorption equilibrium and kinetics of several pharmaceutical compounds (Ronidazole, Metronidazole, Dimetridazole, Diclofenac, Sulfamethoxazole and Carbamazepine) onto granular activated carbon (GAC) from aqueous phase. The adsorption mechanism of the six compounds was dominated by pi-pi dispersive interactions between the aromatic ring of pharmaceutical compound and the aromatic rings of the graphene layers of GAC. Furthermore, the adsorption capacity of GAC can be enhanced by attractive electrostatic interactions. The overall rate of adsorption of the nitroimidazoles was interpreted using diffusional models and the intraparticle diffusion of the nitroimidazoles was the controlling mechanism of overall adsorption rate. Besides, the surface diffusion contributed from 68 to 98 % of total intraparticle diffusion.