Modeling kinetic adsorption in porous media by a two-state random walk particle method

Abstract EN

In this paper, a stochastic approach to address linear kinetic adsorption mechanisms using a two-state particle tracking random walk theory is presented.

During reactive solute transport in porous medium particles are assigned two states: Either mobile (free) or immobile (adsorbed).

By studying the exchange of particles’ states, the mech-anism of adsorption can be better understood.

The kinetics of the particles is modeled with a Markov chain characterized by a transition probability matrix between the two states.

The concept of exchange of particle states of the solute particles is more fundamental than that of relaxing the probability with a retardation factor and it is of great sig-nificance in modeling various reactive transport mechanisms.

A com-puter code (called ADS_2D) has been developed to perform numerical adsorption experiments.

It has been shown from the experiments that adsorption with slow kinetics can not adequately be modeled using a retardation factor.

The fundamental analytical solution deviates from the numerical solution, particularly the spreading of the solute plume.

This is due to the fact that the fundamental analytical solution does not take into account the extra dispersion due to the kinetic reaction.