Volume 3, Issue 7 (July 2006)
Evaluation of the Removal of Heavy Metals from Contaminated Sediment in Continuous Flow Tests with Selective Sequential Extraction
Solutions to heavy metal-contaminated sediment require the understanding of the availability of heavy metals, interaction of the contaminants with soil and sediment particles, and metal retention mechanisms, which are complicated phenomena. The objective of this investigation was to study the removal of heavy metals (copper, zinc, and nickel) from the sediments by employing a biosurfactant rhamnolipid in continuous flow tests. Continuous flow of the biosurfactant in a column was applied to evaluate the feasibility of this type of setup since the configuration simulates the process of soil flushing. In the case of heavy metals, the flowing washing agent is believed to reduce the possibility of readsorption of the metals on to the soil and sediment. In addition, since the distribution of heavy meals between soil and solute is the key to evaluating the environmental impact of the metals, to determining the mobility of metals and to recommending reliable removal techniques, selective sequential extraction tests were used to determine the portion of sediment from which the metal was removed. This method is based on extracting metals with solutions of increasing strengths from different fractions of soils or sediments. Exchangeable, carbonate, reducible oxide, and organic fractions responded to washing techniques while residually bound contaminants are not economical or feasible to remove. This information is vital in proposing the most appropriate conditions for sediment washing.