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, tau (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 tau (K, D, binding parameters) is a measure of the global rate of adsorption while its initial contribute, tau(-1)(l) is related to T (K, infinity, binding parameters). Both tau and tau(-1)(l) 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. (C) 2011 Elsevier Ltd. All rights reserved.