A mass transfer study considering intraparticle diffusion and axial dispersion for fixed-bed adsorption of crystal violet on pecan pericarp (Carya illinoensis)

Abstract

This research was focused on the representation of the fixed bed adsorption of crystal violet dye (CV) on treated pecan pericarp (Carya illinoensis) using a mass transfer approach based on the intraparticle diffusion and axial dispersion. The operation was firstly evaluated in batch mode to determine the external mass transfer coefficients, the equilibrium relation, and the thermodynamic aspects. It was then studied the continuous operation. In this case, the breakthrough curves were modeled by a phenomenological approach, based on the combination of the fluid phase mass balance with intraparticle diffusion (FBID). The results were compared with the Thomas model, which not considers the axial dispersion. The external mass transfer was 4.39 × 10-3 cm s−1. The equilibrium relation was better represented by the Langmuir model. The adsorption process was endothermic, with a maximum adsorption capacity of 639.7 mg g−1. Concerning fixed-bed adsorption evaluation, Thomas and FBID models were able to describe the breakthrough tendencies. Nevertheless, the FBID was used to estimate the axial dispersion coefficient, which ranged from 0.79 × 10-6 to 7.81 × 10-6 cm2 s−1.