Characterization of P-nitrophenol adsorption kinetic properties in batch and fixed bed adsorbers

Abstract

P-nitrophenol (PNP) adsorption in batch and fixed bed adsorbers was studied. The homogeneous surface diffusion model (HSDM) based on external mass transfer and intraparticle surface diffusion was used to describe the adsorption kinetics for PNP in stirred batch adsorber at various initial concentrations and activated carbon dosages. The fixed bed model considering both external and internal mass transfer resistances as well as axial dispersion with non-linear isotherm was utilized to predict the fixed bed breakthrough curves for PNP adsorption under the conditions of different flow rates and inlet concentrations. The equilibrium parameters and surface diffusivity (D s ) were obtained from separate experiments in batch adsorber. The obtained value of D s is 4.187×1012 m2/s. The external film mass transfer coefficient (k f ) and axial dispersion coefficient (D L ) were estimated by the correlations of Goeuret and Wike-Chang. The Biot number determined by HSDM indicated that the adsorption rate of PNP onto activated carbon in stirred batch was controlled by intraparticle diffusion and film mass transfer. A sensitivity analysis was carried out and showed that the fixed bed model calculations were sensitive to D s and k f , but insensitive to D L . The sensitivity analysis and Biot number both confirm that intraparticle diffusion and film mass transfer are the controlling mass transfer mechanism in fixed bed adsorption system.