Study on desorption of heavy metal in sewage-irrigated soil by complexing with saponin
皂角苷络合洗脱污灌土壤中重金属的研究

In this paper,a plant-based biosurfactant saponin was selected to wash up the heavy metals, such as Cu, Cd,Pb and Zn, from the sewage irrigated soil with a series of batch-washing experiments. The results showed that desorption efficiency of heavy metals could be enhanced with the increase of the added saponin concentrations, and could finally reach 43.87 %, 95.11% , 83.54% and 20.34% for Cu, Cd,Pb, and Zn, respectively, by adding 3.0% of Saponin while desorption efficiency by water flushing alone was less than 5%. It was also found that the desorbed amount gradually decreased with the increase of pH values of the soil, which indicated that the high removal only took place in the week acidic environment. The ionic strength slightly had a negative influence on the desorption of Cd ,Cu, but no efforts on Pb,Zn. Comparing the spices transformation of heavy metals before and after desorption in the soil matrix by Tessier method, it was evident that soluble species and carbonated fractions of Cu ,Cd ,Pb ,Zn adsorbed on the soil surfaces were tremendously washed away. As a result, the toxicity and bio-reusability of the heavy metals in soil were significantly decreased.