Evaluation of mass transfer mechanisms involved during the adsorption of metronidazole on granular activated carbon in fixed bed column

Abstract

This work is focused on the transient analysis of the different mass transfer mechanisms during the adsorption of metronidazole on activated carbon packed in a fixed-bed column. The analysis was carried out by modeling the breakthrough curves at different operation conditions with a fixed bed general model (FBGM) that considers the mass transport mechanisms of axial dispersion, convective, external and intraparticle (pore volume diffusion and surface diffusion). The results show that the FBGM model adequately simulated the dynamics of the experimental data under all operating conditions. Moreover, it was demonstrated that the convective mass transport governs the mass transport of metronidazole primarily, while the axial dispersion contributes only up to 5–10 % within the interstitial space of the packed column. The external mass transfer can be less than 5 % of the total mass transport of solute in the liquid phase. Regarding the intraparticle mass transport inside the activated carbon, it was found that surface diffusion is more important than the pore volume diffusion in the dynamic adsorption of metronidazole, and represents 80–100 % of the total intraparticle transport.