皂角苷对红壤和黄褐土中Pb2+、Zn2+的解吸特征

以Pb~(2+)、Zn~(2+)污染的红壤和黄褐土为材料,以皂角苷为解吸剂,研究不同皂角苷浓度(0~20 g·L-1)、p H(3~7)、解吸次数(1~3次)下土壤中重金属的解吸效果。结果表明,随着皂角苷浓度升高,其从土壤中解吸Pb~(2+)和Zn~(2+)的量增大;皂角苷溶液p H越高,对Pb~(2+)和Zn~(2+)的解吸率越低。皂角苷对土壤中Zn~(2+)的解吸率明显高于Pb~(2+),红壤中Zn~(2+)的解吸率最高可达47%,而黄褐土中Zn~(2+)的解析率则为30%。单次解吸,红壤中含量降低最大的是酸溶态的Pb~(2+)和Zn~(2+),分别为38%和34%;可氧化态Zn~(2+)的含量下降较少,约为14%,但下降程度仍高于黄褐土。黄褐土中可还原态Pb~(2+)的含量减少最多,达26%,且各形态的解吸量均显著低于红壤。皂角苷对供试红壤中Pb~(2+)、Zn~(2+)的解吸效果好于黄褐土,可能是红壤与黄褐土的矿物组成和表面电荷性质不同所致。加入皂角苷后,红壤的Zeta电位下降,黄褐土的升高,两种土壤的Zeta电位均向零趋近。

Desorption characteristics of Pb2+ and Zn2+ from red soil and yellow-cinnamon soil by saponin

Incubations of Pb²⁺ and Zn²⁺ in contaminated red and yellow-cinnamon soil were conducted to investigate the effect of saponin on desorption of heavy metals. Various factors such as concentration of adsorbent(0~20 g·L^-1), pH(3~7), extract times(1~3) were studied, the effect of saponins on Pb²⁺ and Zn²⁺ desorption was researched by Zeta potential analysis. Results showed that the desorption amounts of Pb²⁺ and Zn²⁺ enhanced with the increasing of saponin concentration and were negative with the acidity of saponin solution in tested soils. Under the same condition, saponin could desorb more Zn²⁺ than Pb²⁺, the highest desorption rate of Zn²⁺ was 47%, and 30% in the red and yellow-cinnamon soil, respectively. After single desorption, acid soluble Pb²⁺(38%) and Zn²⁺(34%) decreased most in the red soil than in the yellow-cinnamon soil. The declined content of oxidable Zn²⁺ was relatively less(about 14%), but still higher than that in the yellow-cinnamon soil. The reduction of reducible Pb²⁺ was more than other forms of Pb²⁺ in yellow-cinnamon soil, about 26%. The desorption amounts of all forms of Pb²⁺ and Zn²⁺ were significantly lower in the yellow-cinnamon soil than those in the red soil. The desorption effects of Pb²⁺ and Zn²⁺ by saponin were better in red soil than in yellow-cinnamon soil, these were mainly because of the differences of mineral composition and surface charge properties of the two soils.Compared with the red soil, the yellow-cinnamon soil had more constant charge minerals and less variable charge minerals. After adding saponin, the Zeta potential of the red soil decreased and that of the yellow-cinnamon soil increased, and the Zeta potentials of the two soils were generally close to zero.