Kinetics of adsorption of phenol and indole from aqueous solutions on activated carbons: Kinetik der Adsorption von Phenol und Indol aus wäβrigen Lösungen an aktivkohlen

Abstract

In this paper we compare various diffusion models and examine their applicability for description of intraparticle mass transfer during adsorption of phenol and indole from aqueous solutions on activated carbons. Kinetic curves were determined experimentally with a special batch adsorber ensuring complete elimination of laminar boundary layer resistance. The DENT method proposed (Dividing the Experimental into the Normalized Time) allows the calculation of diffusivity for each point of the kinetic curve. For an adequate diffusion model a parameter assumed constant proves to be constant. Surface diffusion with constant diffusivity, pore diffusion with constant diffusivity, combined surface and pore diffusion with constant diffusivities and surface diffusion in two adsorption zones with constant diffusivities do not describe adsorption kinetics observed adequately. Finally, the DENT method was applied to a model in which the surface diffusion coefficient depends on loading exponentially. This approach describes the experimental data most exactly.