Abilities and Mechanisms of GLDA and Its Combined Complexing Agents to Extract As,Cd,Cu and Pb from Soil
In this study,heavy metals combined polluted soil was taken as the study object,and N,N-bis(carboxymethyl)-tetrasodium salt(GLDA)and other biodegradable chelators were combined to explore the extraction efficiency and influence mechanism of single and combined reagents on different heavy metals from soil.The results showed that with the increase of the molar ratio of reagents to heavy metals,the extraction rates of heavy metals increased gradually,and the optimal molar ratio was 5∶1.The abilities of oxalic acid(OA)to extract As and citric acid(CA)to extract Cu were close to those of ethylenediaminetetraacetic acid disodium(EDTA)to extract As and Cu.GLDA had higher extraction abilities for various heavy metals under acidic conditions.With the combination of different reagents,GLDA and OA had the strongest extraction abilities of As,Cu and Pb in soil when the molar ratio was 1∶1,which was 52.4％,75.0％and 89.8％,respectively.The order of extraction ability was Pb＞Cu ≈Cd＞As.While GLDA and CA had the strongest extraction ability of Cd in soil when the molar ratio was 5∶1,which was 95.7％.The chemical fractions of heavy metals before and after extraction showed that GLDA+OA(1∶1)reduced the contents of heavy metals in most chemical fractions,especially the weakly bound heavy metals that are easily transported and absorbed by organisms.
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