Chelant extraction of heavy metals from contaminated soils using new selective EDTA derivatives.
Soil washing is one of the few permanent treatment alternatives for removing metal contaminants. Ethylenediaminetetraacetic acid (EDTA) and its salts can substantially increase heavy metal removal from contaminated soils and have been extensively studied for soil washing. However, EDTA has a poor utilization ratio due to its low selectivity resulting from the competition between soil major cations and trace metal ions for chelation. The present study evaluated the potential for soil washing using EDTA and three of its derivatives: CDTA (trans-1,2-cyclohexanediaminetetraacetic acid), BDTA (benzyldiaminetetraacetic acid), and PDTA (phenyldiaminetetraacetic acid), which contain a cylcohexane ring, a benzyl group, and a phenyl group, respectively. Titration results showed that PDTA had the highest stability constants for Cu(2+) and Ni(2+) and the highest overall selectivity for trace metals over major cations. Equilibrium batch experiments were conducted to evaluate the efficacy of the EDTA derivatives at extracting Cu(2+), Zn(2+), Ni(2+), Pb(2+), Ca(2+), and Fe(3+) from a contaminated soil. At pH 7.0, PDTA extracted 1.5 times more Cu(2+) than did EDTA, but only 75% as much Ca(2+). Although CDTA was a strong chelator of heavy metal ions, its overall selectivity was lower and comparable to that of EDTA. BDTA was the least effective extractant because its stability constants with heavy metals were low. PDTA is potentially a practical washing agent for soils contaminated with trace metals.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China.
Tao
T
Zhang
Jun-Min
JM
Liu
Xiong-Fei
XF
Huang
Bing
B
Xia
Cheng-Yong
CY
Su
Guo-Fan
GF
Luo
Yao-Wei
YW
Xu
Ying-Xin
YX
Wu
Zong-Wan
ZW
Mao
Rong-Liang
RL
Qiu
D002614:Chelating Agents / Q000737:chemistry*; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry*; D052918:Environmental Restoration and Remediation; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*
D002614:Chelating Agents; D019216:Metals, Heavy; D012989:Soil Pollutants; D004492:Edetic Acid
Cu(II); EDTA derivatives; Extraction; Potentiometric titration; Selectivity