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以甘肃白银东大沟Pb、Zn、Cd复合污染土壤为研究对象,通过毒性浸出、形态提取、微观分析等手段,研究了水泥对重金属污染场地的固化稳定化效果及适用性.毒性浸出结果表明,水泥对污染土壤中Cd、Zn能够起到较好的固化稳定化作用,在5%的添加量下,水泥对Cd、Zn的修复效率分别达到99.5%~100%、96.6%~98.8%,而Pb的浸出浓度提高了2.6~5.8倍;在8%的添加量下,水泥对Cd、Zn的修复效率分别达到99.6%~100%,94.4%~97.9%,而Pb的浸出浓度提高了1.9~12.5倍.形态分析结果表明,水泥能够使土壤中的酸可提取态Cd、Zn向残渣态转化,可还原态Pb向可氧化态、残渣态转化,稳定性增强.微观特征分析结果表明,Pb~(2+)、Zn2+、Cd2+这3种离子可以参与水泥的水化反应,生成相应的硅酸盐矿物和氢氧化物,进而对其起到固化稳定化作用.综上,水泥在重金属污染场地修复工程中具有良好的优势,但在具体应用过程中需注意场地及环境条件的特殊性.
Taking Pb, Zn and Cd contaminated soils in Baikanyou East Dagou, Gansu as an example, the effect of solidification and stability of cement on heavy metal contaminated sites was studied by means of toxicity leaching, morphological and microscopic analysis, etc. The results of toxicity leaching , And cement could stably stabilize Cd and Zn in contaminated soil. Under 5% loading, the restoration efficiency of Cd and Zn in cement reached 99.5% -100% and 96.6% -98.8% respectively, While the leaching concentration of Pb increased by 2.6-5.8 times. Under the condition of 8%, the recovery efficiency of Cd and Zn reached 99.6% -100% and 94.4% -97.9% respectively, while the leaching concentration of Pb increased by 1.9% ~ 12.5-fold.The results of morphological analysis showed that cement could convert acid extractable Cd and Zn in the soil into residual state, and the reduction and transformation of Pb to oxidizable and residual state of the soil enhanced the stability.Micro-characteristics analysis showed that, The three kinds of ions Pb 2+, Zn 2+ and Cd 2+ can participate in the hydration reaction of cement to produce the corresponding silicate minerals and hydroxides, which in turn can stabilize them.In summary, Contaminated site restoration project has a good advantage, but in the specific application process In the need to pay attention to the particularity of the site and environmental conditions.