Use of different chelating agents for heavy metal extraction from contaminated harbour sediment

Abstract

This study presents the results of laboratory-scale experimental tests of contaminant extraction from marine sediment slurries. The sediment was collected in a harbour situated in a high-density industrial area, characterised by a high pollution level of heavy metals. The objective of this study was to investigate the effectiveness of selected chelating agents (rhamnolipids, EDDS, EDTA and citric acid) in heavy metal removal from contaminated sediments. To this aim, contamination of the sediment used in this experiment was artificially increased to reach final values of 1250 mg·kg⁻¹ Cu and 2026 mg·kg⁻¹ Pb. The investigated parameters during the washing tests were chelant concentration and overall washing time. To evaluate the sediment characteristics, COD and acid digestion were performed, whereas total organic carbon and heavy metal concentration were determined on the solutions extracted. The results show that the use of EDDS and EDTA gave good extraction efficiencies (up to 95%), unlike the lower removal rates achieved by using citric acid and rhamnolipids. In addition, major cations, mainly Fe and Ca, were found to be strong competitors with the target metals for metal–ligand complex formation.

Keywords:

• sediment remediation
• heavy metal
• washing
• additives
• rhamnolipids