Distributed mass transfer rate for modelling the leaching of porous granular materials containing soluble pollutants

摘要

Studies on the release of chemical compounds contained in porous materials, in contact with a solvent have shown multi-scale dynamics. In the long term, a slight release of substance from the solid matrix is detected. The release kinetics can be correlated to the porous structure. The modelled system consists of a porous granular material containing totally or partially soluble species in contact with water. The mathematical model for intra- and extra-particle transfer is based on the distributed mass transfer rates. The dissolution/precipitation phenomena within the ports and at the particle surface have been taken into account. We have studied release phenomena for an environmental analysis of porous materials. The model has been applied to percolation of Waelz slag. The cations studied are: Na+, K+ and Ca2+. The experimental results show a purely diffusional behaviour for Na+ and K+ whereas the low solubility of Ca2+ limits release. Three pore categories have been considered in the model. The corresponding transfer parameters have been determined by adjustment to the experimental data. Simulations have been carried out for different equilibrium scenarios and for percolation of materials with water. Simulations have shown that a simplified experimental schedule and setup may be used to obtain the same informations about the compounds' mobility. (C) 2000 Elsevier Science Ltd. All rights reserved. [References: 16]