Linear driving force models for dynamic adsorption of volatile organic compound traces by porous adsorbent beds

Models for the dynamic adsorption of volatile organic compound (VOC) traces in air are considered. They are based on the linear driving force approximation associated with various adsorption isotherms characteristic of the couple VOC-adsorbent (Langmuir, Freundlich, Type V and Dubinin–Astakhov (D–A)). This versatile last model is useful not only for VOCs but also for water vapour according to the values of its three parameters. A necessary and sufficient condition for the existence of a constant pattern concentration front is given. The model involving the D–A isotherm provides an interesting case, which is discussed. Theoretical results are illustrated by numerical simulations carried out by means of the finite element method (with Comsol software) and typical behaviours of the breakthrough curves for various adsorbent bed lengths are described.