Extraction of Heavy Metals from Soils Using Biodegradable Chelating Agents

详细信息    查看全文

• 作者：Susan Tandy ; Karin Bossart ; Roland Mueller ; Jens Ritschel ; Lukas Hauser ; Rainer Schulin ; and Bernd Nowack
• 刊名：Environmental Science & Technology
• 出版年：2004
• 出版时间：February 1, 2004
• 年：2004
• 卷：38
• 期：3
• 页码：937 - 944
• 全文大小：176K
• 年卷期：v.38,no.3(February 1, 2004)
• ISSN：1520-5851

文摘

Metal pollution of soils is widespread across the globe,and the clean up of these soils is a difficult task. One possibleremediation technique is ex-situ soil washing usingchelating agents. Ethylenediaminetetraacetic acid (EDTA)is a very effective chelating agent for this purpose but hasthe disadvantage that it is quite persistent in theenvironment due to its low biodegradability. The aim ofour work was to investigate the biodegradable chelatingagents [S,S]-ethylenediaminedisuccinic acid (EDDS),iminodisuccinic acid (IDSA), methylglycine diacetic acid(MGDA), and nitrilotriacetic acid (NTA) as potential alternativesand compare them with EDTA for effectiveness. Kineticexperiments showed for all metals and soils that 24 h wasthe optimum extraction time. Longer times only gaveminor additional benefits for heavy metal extraction butan unwanted increase in iron mobilization. For Cu at pH 7,the order of the extraction efficiency for equimolarratios of chelating agent to metal was EDDS > NTA>IDSA > MGDA > EDTA and for Zn it was NTA > EDDS> EDTA >MGDA > IDSA. The comparatively low efficiencyof EDTA resulted from competition between the heavymetals and co-extracted Ca. For Pb the order of extractionwas EDTA > NTA >EDDS due to the much strongercomplexation of Pb by EDTA compared to EDDS. At higherconcentration of complexing agent, less differencebetween the agents was found and less pH dependence.There was an increase in heavy metal extraction withdecreasing pH, but this was offset by an increase in Caand Fe extraction. In sequential extractions EDDS extractedmetals almost exclusively from the exchangeable, mobile,and Mn-oxide fractions. We conclude that the extractionwith EDDS at pH 7 showed the best compromise betweenextraction efficiency for Cu, Zn, and Pb and loss of Caand Fe from the soil.