Influence of modified Fenton treatment on Organic Matter Content and Heavy Metal Mobilization

This study presents the results of laboratory experimental modified Fenton treatments conducted on marine sediments collected in a harbour situated in a high density industrial area, characterized by a high pollution levels of hydrocarbons. Fenton’s-like oxidation proved to be effective in the remediation of soils contaminated by different pollutants, but very little information is given in case of marine sediments. The investigated parameters were: the H2O2 dose, the pH of the reagents and the effect of a phosphate salt addition. To evaluate sediment’s characteristics COD, TGA and DTA under O2 atmosphere analyses were performed while TOC, COD, pH and Eh were measured on the liquid. Sequential extractions were also performed on the treated sediment to assess metal mobility. The attention was particularly focused on the sediment’s thermal behaviour, because Fenton-like oxidation could also become a pre-treatment of a successive thermal treatment. In our case, the pre-treated sediment would have easier-to-handle characteristics and the lower temperatures generated during the combustion of the organic contaminants, would limit the mixing with inert material. As the conditions generated during the treatment change the redox potential of the sediment an evaluation of the heavy metal mobilization was also performed. Results indicate that the treatment was able to change the organic matter to a less hydrophobic state, to destroy part of the carbon and to lower the COD of the sediment. In addition the treated sediment showed easier-to handle characteristics, reduced caking and lower aggregation capacity. However some mobilization of Cu and Zn occurred while the concentration of Fe lowered.