Analysis Of Adsorption & Migration Behaviour Of Contaminants In Aqueous Phase Through The Desert Soil Porous Medium

Abstract

The main focus of this project was to investigate transport and adsorption of contaminants (radionuclide) on loamy desert soil through modeling the system by the Finite Element Method (FEM) and verification using experimentation. The Advective dispersion reaction (ADR) mechanism and pore diffusion model were employed to describe the contaminant transport and adsorption in soil medium. Partial Differential Equations (PDE) obtained from unsteady state mass balance consisted of convective diffusion, solute adsorption, and dispersion terms for the ADR equation. In pore diffusion models, the shape of the soil particles were assumed to be spherical and mass balances were performed on the soil phase as well as on the liquid phase. Equilibrium and kinetic experiments were conducted using lead as a surrogate radionuclide. Initial batch equilibrium adsorption experiments revealed that the system follows Langmuir adsorption isotherm. The diffusion coefficient was evaluated by nonlinear regression analysis on kinetic experimental data, which was used as a parameter in the ADRE. The other required parameters for the model such as Langmuir constant and maximum adsorption capacity of the adsorbent were evaluated from batch experiments. Darcy's law was coupled with the continuity equation to calculate the pressure drop along the length of the column and the velocity. Adsorption isotherm equation and Darcy's law was internally coupled with "Advective Dispersion Reaction" Equation and the resulting set of unsteady non linear Partial Difference Equation (PDE) were solved using "COMSOL MULTIPHYSICS - 3.2".