Assisted Washing for Heavy Metal and Metalloid Removal from Contaminated Dredged Materials

In the present study a chemical washing process was applied to dredged sea and river sediments. Five chelating agents (ethylenediaminetetraacetic, nitrilotriacetic, citric, [S,S]-ethylenediaminedisuccinic and oxalic acids), three surfactants (sodium dodecyl sulphate, cetylpyridinium chloride and saponin Q), as well as monobasic potassium phosphate were used as the extracting agents. The effect of sonication was also tested as a conditioning step to couple with chelant-based extraction. The extraction experiments were performed in both single and multiple washing stages. The results indicated that, for given experimental conditions, the remediation efficiency was strongly dependent on the specific contaminant under concern, with contaminant speciation and distribution in the solid matrix as well as affinity for the extracting agent playing a major role in the decontamination process. In this respect, the study also showed that in the presence of multiple contaminants the use of a single extraction agent is not sufficient to attain adequate quality levels for the treated sediment.