Heavy metals removal from dredged sediments using electrokinetics process
Résumé
Dredging practices constitute a challenge for developing and maintaining harbor and fluvial activities. They also present a contamination risk of coastal waters which can affect the ecosystems. The unsuitability and restriction to marine disposal of dredged sediments leads ultimately the managers to provide a treatment ashore because of the great volume of material to be treated.So, Heavy metals fate and transport in contaminated sediments involve difficult risk assessment and remediation challenges.Laboratory electromigration experiments show the efficiency of such process on heavy metals removal from fine sediments. Analysis of solid fractions after test allows to highlight the mobility of heavy metals inside the sediment sample. Among all the additives tested for metal removal, nitric acid showed the best removal efficiency, but citric acid, which is environmentally friendly, was also very interesting due to its buffering and chelating capacities. Results revealed that adding a strong inorganic acid (Nitric Acid) into the aqueous fluid was more effective than a weak acid (Citric Acid), but the complexing citric acid was promising for longer treatment. The Citric Acid as enhancing-process fluid provides significant heavy metals removal. Zn and Cd are easy-removed from natural sediment which presents more metals-affinity than model sediment for which removal was more significant. Further results showed that combining an acid and a surfactant allowed simultaneous removal of heavy metals and PAHs.
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