Experimental assessment of heavy metal extraction from contaminated italian harbour sediment by rhamnolipid

This study presents the results of laboratory scale experimental tests of contaminants extraction from marine sediment slurries. The sediment was collected in a harbour situated in a high density industrial area, characterized by a high pollution level of heavy metals. The contamination of the sediment used in this experimentation was artificially increased to reach final values of 1250 mg/Kg of Cu and 2026 mg/Kg of Pb. The objective of this study was to investigate the effectiveness of selected chelating agents (Rhamnolipid, EDDS and Acid Citric) in heavy metals removal from contaminated sediments. The investigated parameters during the washing tests were the chelants concentration and the overall washing time. To evaluate sediments characteristics COD and acid digestion were performed, while TOC and heavy metal’s concentration were determined on the solutions extracted. Results show that the use of EDDS and EDTA allows the reaching of good extraction efficiencies (up to 95 %) unlike lower removal rates reached by the Acid Citric and Rhamnolipid, probably due to very low values of constants of the corresponding metal-additive complexes. Finally, major cations, above all Fe and Ca, were found to be strong competitors with the target metals for the metal-ligand complexes formation.