PREDICTING MULTICOMPONENT ADSORPTION AND TRANSPORT OF FLUORIDE AT VARIABLE PH IN A GOETHITE-SILICA SAND SYSTEM

Environmental impacts of soil pollution are greatly affected by the mo bility and migration contaminants in soil. Multicomponent transport pr ocesses can play an important role in this migration. Therefore, model ing of transport processes and prediction of contaminant mobility as a function of soil properties can be a useful tool in risk evaluation. This work shows how a mechanistic model of ion adsorption an variable charged surfaces combined with a convective dispersive solute transpor t model was used to predict multicomponent transport of fluoride at va riable pH in a goethite-silica sand column. In order to show the poten tial of this type of modeling, the chemical properties of the column m aterial used in the transport calculations were not derived from measu rements on the material itself, but predicted from independent data on synthetic goethite and silica. In this way the only parameters needed to predict the transport of fluoride and acidity were the chemical co mposition of the infiltrating solution, and the surface areas of goeth ite and silica present in the column. Although no chemical data of the actual column material were used, the agreement between predicted and experimental fluoride and pH breakthrough curves was very good. This shows that this type of modeling can be very useful for the understand ing of multicomponent transport processes.