one of the most common contaminants in the environment and has chronic toxicity.
A number of techniques have been developed to remove heavy metals from contaminated sites, including ex-situ washing with physical-chemical methods and in-situ phytoextraction. In the ex-situ washing methods, chelating agents or acids are used to enhance heavy metals removal. Ethylene- diaminetetraacetic acid (EDTA) is the most commonly used chelate because of its strong chelating ability for different heavy metals. Besides chelating chemicals, dissolved organic carbon (DOC) in the leachate also shows the ability to form complexes with heavy metals. Indeed, water-soluble organic matter may play a significant role in enhancing heavy metal leaching to groundwater.(1)