Extension of Dubinin’s Theory to Adsorption from Aqueous Solutions

Adsorption of sparingly soluble organics from aqueous solutions, by activated carbons, can be described within the framework of Dubinin’s theory by using a modified Dubinin-Radushkevich-Kaganer (DRK) equation, where relative pressures are replaced by relative concentrations. With respect to the descriptions based on the Langmuir model and similar expressions, this approach has the advantage that it allows predictions on the basis of simple physico-chemical properties of the solid and of the adsorbate. Preliminary experiments indicate that in the case of dilute binary mixtures, the model of independent coadsorption, based on the DRK equation, applies. However, more experimental evidence is needed to confirm this potentially very useful approach in filtration technology.

Keywords: Dubinin’s theory; adsorption; aqueous solutions; binary mixtures