Reactive-transport modelling of electrokinetic extraction of heavy metals from marine sediments

This work presents a one-dimensional numerical model to simulate the electrokinetic remediation of real contaminated sediments characterized by a heterogeneous solid matrix and aged heavy metal pollution. The numerical model couples a transport model able to simulate electromigration and electroosmosis with a geochemical model which calculates aqueous speciation, precipitationdissolution, adsorption and surface complexation reactions. Laboratory scale experiments were carried out to validate the model. We identified the acid buffering capacity as the most significant factor for the extraction of heavy metals from the sediments as their speciation and mobility are strictly dependent on sediment capacity to prevent the pH shift to the acidic range. A good agreement was obtained between simulated pH and metal profiles and experimental data