Removal of heavy metals from contaminated soils with fresh and recycled EDTA
EDTA及其回收溶液治理重金属污染土壤的研究

Experiments showed that EDTA has most effectiveness in removing heavy metals from both contaminated soils; however, EDTA is relatively expensive and cannot be readily degraded by conventional biological treatment processes. Thus, EDTA may be recycled and reused. Species distributions of heavy metals in the extraction solutions were analyzed with MINTEQA2 computer programme at working condition, metal-EDTA was found to be predominant fractionation among metal species. Metals and EDTA were separated efficiently by Na2S addition from the extraction solution. After that, the recycled EDTA was reused to remove heavy metals from contaminated soils. The extracting and recycling procedures were repeated four times. Although the recycled EDTA showed the leaching ability from both contaminated soils, the extraction efficiencies of heavy metals with the recycled EDTA were lower than those with the fresh EDTA because of the residual Na2S and lower concentration of recycled EDTA than before.