  A mathematical model is developed for the process of mass transfer from a
fluid flowing through a packed column. Mass loss, whether by absorption or
adsorption, may be significant. This is appropriate for example when removing
contaminants from flue gases. With small mass loss the model reduces to a
simpler form which is appropriate to describe the removal of
contaminants/pollutants from liquids. A case study is carried out for the
removal of CO2 from a gas mixture passing over activated carbon. Using the
experimental parameter values it is shown, via non-dimensionalisation, that
certain terms may be neglected from the governing equations, resulting in a
form which may be solved analytically using a travelling wave substitution.
From this all important quantities throughout the column may be described;
concentration of gaseous materials, amount of material available for mass
transfer, fluid velocity and pressure. Results are verified by comparison with
experimental data for the breakthrough curve (the amount of carbon measured at
the column outlet). The advantage of the analytical expression over a purely
numerical solution is that it can easily be used to optimise the process. In
the final section we demonstrate how the model may be further reduced when
small amounts of contaminant are removed. The model is shown to exhibit better
agreement than established models when compared to experimental data for the
removal of amoxicillin and congo red dye from water.
