Parameter estimation for kinetic interactions during colloid-facilitated transport in a porous medium

The analysis of experimental data on colloid-facilitated transport is in general not a simple task. Usually, only the breakthrough curve for the total mobile contaminant concentrations, i.e. the sum of the concentration of free species and contaminants sorbed to mobile colloids, is available while the time-dependent concentration distribution of the different species in the system is unknown. Since the breakthrough curve of mobile contaminants is a ''lumped'' result of different processes, separation of the effect of these different processes and estimation of the relevant model parameters on the basis of experimental data is not a trivial problem. In this contribution a model for ID coupled colloid and contaminant transport in a porous medium is presented. Incorporated in the model are kinetic terms for interactions between: contaminants and the solid matrix, colloids and the solid matrix, and contaminants and colloids. A least squares procedure has been implemented to estimate the kinetic interaction parameters from measured and calculated breakthrough curves. The procedure has been applied to a column experiment. Kinetic interaction parameter values and their covariance matrix have been estimated. It is shown that this procedure assists in identifying relevant processes and estimating model parameters that fit the experimental data of colloid-facilitated transport.