Washing of heavy metal contaminated soil around a lead-zinc smelter by several chelating agents and the leached soil utilization

Batch leaching experiments were conducted to examine the effects of different chelates( EDTA,EDDS,EGTA and NTA) on extraction Cd,Cu,Zn and Pb from different contaminated soils and the utilizable value of soil after leaching. The redistributions of heavy metals were determined using the BCR sequential extraction procedure before and after treatment. The utilizable value assessment of leached soil was also studied by the ryegrass pot experiment. The results showed that for the four kinds of heavy metal,Cd was the easiest to leaching and the leaching efficiency of different chelates on contaminated soil followed the sequence of EDTA NTA EDDS EGTA. Among the four chelates,i. e. EDTA,EDDS,EGTA and NTA,EDTA was the best effective in removing Cd,Cu,Zn and Pb,with removal rate being 90. 98%,42. 10%,56. 98% and 52. 03%. Enzyme activity assays showed that leaching with EDTA had a distinctly positive impact on soil microbial and enzyme activity,while leaching with NTA had less impact. Taking into account comprehensively extraction effectiveness,utilizable value and cost of the agents,EDTA was suitable for heavy metals extraction from contaminated soil.