The Combination of Na2EDTA and Reducing Organic Acid on Remediation of Soil Contaminated by Heavy Metals

Washing tests using a typical chelating agent (Na2EDTA) and two reducing organic acids (oxalic and ascorbic acid) were conducted to remediate soil contaminated by heavy metals at a former metal smelter. Removal efficiencies of arsenic, cadmium, copper and lead under Na2EDTA washing enhanced by reducing organic acid were tested with washing time and steps. Results showed that the addition of reducing acid increased the overall removal efficiencies of metals in some extent. The combination of Na2EDTA and oxalic acid was effective in removing arsenic and copper, while the combination of Na2EDTA and ascorbic acid was more effective in removing cadmium and lead. Washing process included the rapid desorption (20~60 min) and the rate-limited dissolution. Most available contents of metals were extracted within an hour. Multi-step washing was more effective than single washing. However, secondary washing was sufficient for remediation. So the washing conditions should be identified prudently.