Adsorption and mass transfer in granular porous membranes/media due to inserted volatile materials

摘要

Here we study experimentally diffusion mass transfer and adsorption/desorption processes of vapor of sublimating volatile materials located below a granular porous membrane/medium. The adsorption kinetics of three different materials: camphor, naphthalene and 2,4-Dinitrotoluene (DNT) was explored. These chemically different materials with significant differences in volatility were chosen to elucidate the common mechanisms of their physisorption in porous media and to establish a novel method which allows one to use such model materials as camphor and naphthalene for predictions relevant to such low volatility materials as DNT, etc. Accordingly, the experimental results were rationalized in the framework of the adsorption/desorption theory to establish the kinetic and equilibrium adsorption/desorption parameters. It should be emphasized that the transient adsorption/desorption theory developed in the present work is novel. Experiments were conducted at different temperatures below melting points of three volatile substances, with morphologies of the clusters of the adsorbed molecules being explored and the adsorbed mass measured versus time. Two experimental methods were implemented. The first setup revealed the kinetics of adsorption/desorption of different substances onto the sand surface, and enabled an estimate of the kinetic constants, and the second setup provided an additional insight regarding the simultaneous processes of diffusion and adsorption/desorption within granular media. The theoreticalumerical predictions are shown to be in good agreement with the experimental data, as well as the agreement between the two experimental methods used to measure the adsorbed mass on sand was quite satisfactory.