Mobilization of potentially toxic elements from harbor contaminated sediments capped with mixtures of hematite and active carbon

In this study, the immobilization of potentially toxic elements (PTEs) by two mixtures of hematite (HT) and activated carbon (AC) was evaluated. For the experiments, a 10-cm layer of contaminated sediment was capped with a 10-cm layer of these minerals (the control was not capped), and a 10-cm layer of seawater was placed on top. Three different sceneries were considered as a good remediation technique: (a) when the mobilization of the PTEs from the contaminated sediment did not occur (Cr and Cu); (b) when mobilization occurs but only reaches the 10-cm capping layer (Pb and Zn); and (c) when mobilization occurs and the amount of PTEs reaching the water column is minimal or insignificant (Ag), compared with the mobilization without active capping layer (control). Otherwise, As transference from the capping layer into overlaying seawater was observed. In addition, the estimation of diffusive flux of this element, based on Fick’s first law, indicated a flux from the capping layer to the sediment layer, proving that the investigated minerals were not a correct choice for reducing the concentrations of this specific pollutant.