Linear driving force analysis of adsorption dynamics in stratified fixed-bed adsorbers

Abstract

The linear driving force (LDF) model has been used to study adsorption dynamics in many gas and liquid phase applications and is particularly useful in the simulation of cyclic sorption operations. It is computationally a simpler alternative to the more complex models that use partial differential equations to represent diffusion within the sorbent particle. In this study, an LDF model that takes into account sorbent particle size distribution (PSD) within the adsorber is developed to study adsorption dynamics in fixed-bed adsorbers with different geometries and layering of particles of different sizes. Phenol and 2, 4-dichlorophenol (DCP), two trace contaminants in water supplies and wastewaters with differing adsorption characteristics, are studied in different adsorber configurations to determine the effects of bed geometry on bed capacity utilization. The convergent tapered stratified bed with eight granular activated carbon (GAC) particle sizes was found to enhance bed capacity utilization by 20% and 50% respectively for phenol and DCP over that of conventional stratified cylindrical bed adsorbers. The LDF model was found to provide good prediction and representation of adsorption dynamics in stratified fixed-bed adsorbers at much reduced computational effort. Sensitivity analyses indicate that the adsorption affinity of solute, bed geometry, and particle stratification play key roles in the enhancement of bed capacity utilization in fixed-bed adsorbers.