Kinetics of Adsorption on Activated Carbon: III. Natural Organic Material

Abstract

Adsorption kinetics of a fulvic acid (FA) were investigated in detail. Based on experimental equilibrum data, the mixture was subdivided into two pseudocomponents with different adsorbabilities and one nonadsorbable fraction. Thus the impact of the initial concentration on the overall isotherm could be described well. However, equilibrium data of the FA after preadsorption were poorly predicted. Minicolumn experiments allowed for the determination of external mass transfer coefficients of the adsorbable pseudocomponents. The results also yielded an estimation of the effective diffusivity and the average molecular size of the FA in the bulk liquid phase. Intraparticle diffusivities were evaluated from batch kinetic experiments. The overall concentration change with time was well described by the film‐homogeneous diffusion model, while the behavior of the pseudocomponents could be described more closely by the filmheterogeneous diffusion model. The applicability of the models to predict a minicolumn breakthrough curve is discussed.