Application of biosurfactants and periodic voltage gradient for enhanced electrokinetic remediation of metals and PAHs in dredged marine sediments
Résumé
Dredged harbor sediment co-contaminated by heavy metals and polycyclic arom. hydrocarbons (PAHs) was subjected to enhanced electrokinetic treatments, using a mixt. of a chelating agent (citric acid CA) and a surfactant as additives in the processing fluids. We tested various operating conditions (at 1 V cm-1): different CA concns., applying a periodic voltage gradient, pre-conditioning the sediment with the additives, and replacing the synthetic surfactant Tween 20 (TW20) by biosurfactants. Increasing the CA concn. was favorable for both metal and PAH removal. Applying a periodic voltage gradient assocd. to a low concn. of CA and TW20 provided the best results for Zn, Cd and Pb removal and also for removal of the 16 priority PAHs. Promising results were obtained with solns. contg. rhamnolipids (0.028%) and a viscosin-like biosurfactant produced by Pseudomonas fluorescens Pfa7B (0.025%), assocd. to a periodic voltage gradient. Although the rhamnolipid and the viscosin-like compds. involved a higher elec. current than TW20, metals were less removed from the sediment. The electroosmotic flow was lower when we used biosurfactants, hence a less effective effect on PAH removal.