Simultaneous And Efficiently Eluting Of Heavy Metals And PCBs In Soils By Mixed Eluent

Nowadays, electronic wastes have grown faster than ever because of the rapid replacement for electronic products being more common, which is a side effect of technology development. In the meantime, in progress of dismantling and incinerating these electronic wastes, ecological system and human health could be severely damaged by heavy metals like Cu, Pb, Cd and persistent organics like PCBs and PBDEs that were transmitted from electronic wastes into soil and groundwater. For the time being, few studies about soil remediation have been carried out in China, and most of them are targeted for only one single contaminant, instead of for combination of heavy metals and hydrophobic organics. Therefore, researches of complex contaminated soil remediation play a significant role for modern society and fragile ecosystem.This dissertation consisted of three fundamental experiments to find out an effective and efficient solution to cope with mentioned problem. First of all, by applying the method of oscillation balance for batch, saponin has demonstrated that it has best elution effect among other eluents for heavy metals- polychlorinated biphenyls polluted soil. Secondly, saponin, tween-80 and citric acid were composed as mixed eluent considering the influence of different factors such as concentration ratio, p H and eluting time, etc., to examine the best elution condition. Thirdly, an additional method of leaching through the soil column, the institute was mixed eluent under more realistic conditions for a greater amount of contaminated soil leaching effect, and to consider the amount of eluent, leaching rate, leaching methods factors affecting leaching effect, obtained the optimum leaching conditions. The main findings are as follows:(1) By comparing the elution effects for co-contaminated soils with heavy metals(Cu, Pb, Cd) and PCBs by concentration of 5g/L and 20g/L of dodecyl dimethyl betaine, cocamidopropyl betaine, sodium lauryl amphoteric imidazoline, cocoampho imidazoline, saponin and citric acid, and found that saponin has a comprehensive elution effect to heavy metals and PCBs.(2) By the research of the elution effects for co-contaminated soils by different concentrations of saponin mixed with Tween-80, we found that when the concentration of saponin and Tween-80 are 12g/L and 10g/L, the elution of the four contanmination has the best effect. And the elution ratio of Cu, Pb, Cd and PCBs are 54.35%, 61.13%, 86.33% and 80.27%.(3) By the research of the elution effects for co-contaminated soils by different concentrations of citric acid mixed with 12g/L saponin and 10g/L Tween-80, we found that when the concentration of citric acid is 5g/L, we get the best elution effect. A strategic result can be found that the elution reaches its best condition when the ratio of saponin, Tween-80 and citric acid in the mixed eluent are 12, 10 and 5g/L in circumstance of p H 5.0, being eluted 6 hours, and the elution ratios of Cu, Pb, Cd and PCBs are 88.32%, 82.75%, 94.89% and 80.56% respectively, which achieve the efficiently simultaneously elution of heavy metals and hydrophobic organics in the co-contaminated soils. And the elution ratio of the heavy metals R1 and R2 are more than R3 and R4.(4) By the research of the influence of elution effect in the experiment of soil column leaching by the factor such as ratio of soil and sand, the amount of eluent, the rate of leaching and the way of leaching. And found that when using 700 ml mixed elution with 12g/L saponin, 10g/L Tween-80 and 5g/L citric acid,whose p H is 5, to wash the co-contaminated soils with heavy metals and PCBs by the way of soil column leaching, if the ratio of soil and sand is 1/3, the rate is 2ml/min, the elution ratio of Cu, Pb, Cd and PCBs are 92.87%, 86.68%, 96.23% and 81.34%.