皂角苷对土壤中重金属的解吸过程及机制

以Pb、Cd、Zn复合污染土壤为供试样品,采用振荡法考察皂角苷对土壤中重金属的解吸效果、解吸过程以及解吸前后的形态变化,并采用傅立叶红外变换光谱分析了解吸机制,结果表明：皂角苷质量分数为3%时,对Pb、Cd、Zn的解吸率分别为10.86%、41.25%和8.45%,再增加皂角苷浓度,其解吸效果无明显增加;Pb、Cd、Zn的解吸过程均分为快反应和慢反应2个阶段,均为非均相扩散过程;经皂角苷解吸后,Pb的残渣态和碳酸盐结态含量分别下降42.31%和35.39%,水溶态及可交换态含量稍有增加,其他形态含量无明显变化;Cd的水溶态及可交换态、碳酸盐态、Fe-Mn氧化物态、有机结合态和残渣态含量分别下降48.25%、58.70%、54.39%、32.16%和41.82%;Zn的碳酸盐态含量降低29.19%,水溶态及可交换态含量显著增加,其他形态无明显变化;皂角苷是通过羧基基团与重金属配位形成可溶络合物而达到解吸效果的,与Zn的络合能力相对较弱。

Study on the Process and Mechanism of Heavy Metals Desorption from Contaminated Soil by Saponin

The soils contaminated with Pb、Cd、Zn were selected as test samples.Oscillation tests were conducted to study the effect,process and speciation variety of heavy metals desorption by saponin.The Fourier transform infrared spectroscopy method was adopted to investigate the desorption mechanism.The results showed that with 3% of saponin applied to the soil,desorption efficiencies of Pb、Cd and Zn were 10.86%,41.25% and 8.45%,respectively.The desorption efficiencies did not increased obviously with the content of saponin further increased.The desorption process of Pb、Cd、Zn could be divided into two phases： the fast phase and slow phase,which were both diffusion process of heterogeneous phase.After the desorption by saponin,the contents of the residual and carbonate fractions of Pb decreased by 42.31% and 35.39%,respectively;the content of soluble fraction slightly increased,and others did not change obviously.The concentrations of the soluble,carbonate,Fe-Mn oxide,organic matter and residual fractions of Cd reduced by 48.25%,58.70%,54.39%,32.16% and 41.82%.The content of the carbonate fraction of Zn decreased by 29.19%;the content of soluble fraction markedly increased,and others did not change significantly.Saponin desorbed heavy metals through complexing with heavy metals,and the ability of saponin complexing with Zn was weaker.