Reusing chelating agents to wash metal-contaminated soils

We studied a chemical treatment in order to reuse aqueous solutions of chelating agents for trace-metals extraction from a contaminated soil. FeS, air-sparging and Ca3(PO4)2 were successively used to precipitate Cu, Ni and Pb from chelates in soil extracts and recover polyaminocarboxylates in their Ca-form. The results of batch experiments showed that the reused extracting solutions kept their high extraction efficiency after 3-runs. Chelant and solution losses were stable on each run and ranged from 10 to 20%. The low solubility and the stability of FeS in mild acidic conditions make it a promising reagent for metal precipitation and chelant recovery in soil-washing.