Pollutants adsorption from aqueous solutions: the role of the mean lifetime

The adsorption of chromate ions from aqueous solutions onto the novel CTAB–silica–gelatin composite has been studied with a non-conventional method. We show that the mean lifetime, ττ (K, D, binding parameters) provides a compact and convenient description of adsorption measurements. Here K is a parameter that measures the adsorption at the interface, D   is the bulk diffusion constant for the fluid in the pore space, and the binding parameters indicate all the parameters that characterize the kinetics of adsorption sites. The practical utility of the method is shown discussing in detail two case limits very useful in treatment of experimental data. In particular we show that the function ττ (K, D  , binding parameters) is a measure of the global rate of adsorption while its initial contribute, τI−1 is related to ττ (K  , ∞∞, binding parameters). Both ττ and τI−1 can be used to study, via Laplace transform representation, the disappearance of chromate ions from the solution. The formula obtained is a reasonable approximation of the experimental adsorption data.

► The lifetime ττ provides a convenient and compact way to interpret the adsorption results.
► The parameter ττ can be used independently from the geometry of the solid adsorbent.
► The overall and initial values of ττ are related to the adsorption mechanism.
► Laplace Transform is used to obtain an approximate formula able to describe how the solute concentration varies over time.