Reclamation of EDTA by sodium tetraethylenepentamine-multi dithiocarbamate after soil washing process with EDTA |
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| Authors: | Yan Wang Bingru Zhang Tianlin Deng Fengting Li |
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| Institution: | 1.State Key Lab of Pollution Control and Resource Reuse, UNEP-Tongji Institute of Environment for Sustainable Development, College of Environmental Science and Engineering,Tongji University,Shanghai,China;2.Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering,Tongji University,Shanghai,China |
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| Abstract: | Ethylenediaminetetraaceticacid (EDTA) has been proven to be an efficient soil washing liquid to remove metal contaminants from soils. However, EDTA may cause secondary pollution due to its low biodegradability if it is not recycled or destroyed in the washing process. Thus, it is necessary to recycle and recover EDTA for sustainable use. In this paper, the extracting performance of fresh EDTA was firstly studied as a function of EDTA concentration, liquid/sediment (L/S) ratio and pH of the solution, and also extraction time. Then sodium tetraethylenepentamine-multi dithiocarbamate (TEPA-DTC), a heavy metals capturing agent, was synthesized on the base of the research of LIU-Lihua. Compared with Na2S and DDTC, TEPA-DTC shows strong chelating capacity, because it has functional groups of dithiocarbamate that could strongly chelate heavy metals and capture metal ions from Me-EDTA to form precipitates, allowing us to reclaim the EDTA during the process of soil washing. Three divalent heavy metals were investigated (Pb, Cd, and Cu). These three metals could almost precipitate completely with TEPA-DTC under the dosage of 300 mg/l, and EDTA was regenerated. The recovered EDTA was used again in three cycles of soil washing, and the amount of heavy metals extracted just slightly decreased each cycle. |
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