Prediction of multicomponent adsorption behavior in activated carbon adsorbers: kinetic aspects

Although the concentrations of solutes are very low in water treatment, it cannot be expected that the film-diffusion model predicts breakthrough behavior satisfactorily, for the following reasons: most of the solutes have less favorable isotherms than p-nitrophenol or p-chlorophenol; many solutes are much larger molecules and hence have a much higher internal diffusion resistance than p-nitrophenol or p-chlorophenol; and displacement effects cause a much higher internal resistance than expected from single-solute data. Therefore, internal diffusion resistance has to be incorporated into the film-homogeneous diffusion model. All parameters needed in this model can be obtained from batch reactor tests. Multi-solute systems may be regarded as a single-solute system or a bi-solute system, respectively, if all solutes except one or two are present in very different concentrations; and/or have a comparatively small affinity to activated carbon; and/or have a comparatively small internal diffusion coefficient.