Is it time to move on from the Bohart-Adams model for column adsorption?

Abstract

The Bohart-Adams model provides a standard expression for the breakthrough curve of contaminant at the outlet of a packed column. It is a basic building block for analysis and computations in the field. In this paper we demonstrate that this model can provide highly inaccurate results and that its well-documented success is shown to be a result of using known system parameters as unknown fitting parameters, permitting constant values to vary, permitting unphysical values (such as negative adsorption sites) and an acceptance of poor fits. Using correct system parameters we provide examples where the Bohart-Adams prediction for the breakthrough time is more than double the experimentally observed value. It is shown that the symmetric exponential form is an inevitable consequence of a mathematical model consisting of a balance between advection and a mass sink, where the sink is of the Langmuir form. Finally, we briefly mention a model that fits a wider range of experimental data without resorting to unphysical and inconsistent parameter values.