Extraction of metals using EDTA, DTPA and NTA and its effects on metals' fractions.

Metals in polluted soils from disused copper mining area were extracted using EDTA,DTPA and NTA.After extraction,metals(Cu,Zn,Pb,Fe and Al)in different phases were analyzed by modified BCR sequential extraction procedure.The extraction efficiency of metals increased evidently at the presence of EDTA,DTPA and NTA.The extraction efficiency was 8.08(EDTA),8.15(DTPA)and 5.40(NTA) times of the control for Cu,and 10.5(EDTA),5.75(DTPA)and 3.63(NTA)times of the control for Zn.Mg was only slightly affected compared to other elements,and its extraction efficiency was 1.28(EDTA),1.21(DTPA)and 1.12(NTA)times of the control.However,Mn and Fe were impacted severely,and the extraction efficiency of Fe was 11.3(EDTA),21.7(DTPA)and 2.33(NTA)times of the control.All the fractions tested could be affected by the extraction using EDTA,DTPA and NTA.Exchangeable fraction and reducible fraction of the metals(Cu,Zn,Pb)significantly reduced due to the extraction with the three ligands.After extraction,reducible fraction of Zn was only 19.9%(EDTA),18.6%(DTPA)and 22.3%(NTA)of the control and exchangeable Pb was 64.3%(EDTA),49.5%(DTPA)and 82.4%(NTA)of the control.For EDTA and DTPA treatment,reducible fraction of Cu was only 71.9% and 75.1% of the control.Extraction with the three ligands also resulted in the decrease of the contents of exchangeable/acid-extractable Fe and Al.The extraction using organic ligands(EDTA,DTPA and NTA) resulted in the increase of the dissolution of both the target heavy metals(Cu,Zn,Pb)and other metals(Al and mineral elements -Ca,Mg,Mn,and Fe),and the extraction decreased the bioavailable fractions of the heavy metals.