地质聚合物固化稳定化重金属复合污染土壤
Soil of heavy metal composite pollution by geological polymer stabilization
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摘要: 以污染土壤部分替代偏高岭土，在碱激发剂的作用下制备地质聚合物稳定化处理Pb、As、Cd复合污染土壤，研究了其稳定化效果及处理后固化体中重金属的赋存形态。结果表明：污染土壤部分替代高岭土降低了固化体抗压强度，从力学性能上看，土壤掺量低于50%时，能满足建筑材料的强度要求（>10 MPa），掺量为60%仅能满足固废填埋要求（>5 MPa），土壤掺量?70%均不能满足要求。随着土壤掺量增加，对土壤中重金属的稳定化效果也逐渐降低，当土壤Pb、As和Cd浓度分别为600、80和22 mg·L-1（HJ 350-2007B）时，土壤掺量在20%～50%，固化体中3种元素浸出浓度均低于浸出标准；当土壤掺量达到60%时，Pb的浸出浓度不能满足标准要求，当土壤掺量增加至70%，固化体中Pb、Cd浸出浓度均超标。固定土壤掺量为30%，随着污染土壤中重金属含量的增加，浸出浓度也增加：土壤中3种重金属浓度为HJ 350-2007B时经过30 d的稳定化处理，浸出浓度满足标准要求；而当浓度达到HJ 350-2007B的2倍时，Pb浸出浓度超标；达到HJ 350-2007B的3倍时，3种Pb、As和Cd均超出浸出标准。固化体中Pb、As、Cd的形态研究表明，外源重金属进入土壤后多以活性较高的形态存在，经过固化稳定后活性态占比降低、残渣态占比增加。Abstract: Geopolymer obtained from a polluted soil substitute partial metakaolin catalytic synthesis by the alkali activator was used to stabilize Pb, As and Cd. The stabilization effect and the speciation of heavy metals in the cured body were studied. The results show that the partial replacement by soil reduces the compressive strength of the cured body. However, from the mechanical properties, it can meet the strength requirements of building materials (greater than 10 MPa) when the content of soil is less than 50%, and it can meet the solid waste landfill requirements (greater than 5 MPa) when the content of soil reaches 60%, while it cannot meet the requirements when the soil content is higher than 70%. The stabilization effect of heavy metals in soil decreased gradually with the increasing content of soil. Pb, As and Cd maintained at 600, 80 and 22 mg·kg-1(HJ 350-2007B) respectively, the leaching concentrations of three elements in the solidified body are lower than the leaching standard when the soil content range from 20% to 50%, and the leaching concentration of Pb cannot meet the standard requirements when the soil content reaches 60%. Additionally, Pb and Cd leaching concentration exceeded when the soil content higher than 70%. When the content of fixed soil maintained at 30%, the leaching concentration increased with the increasing heavy metal. When the concentration of three heavy metals reached HJ 350-2007B, the leaching concentration could meet the standard requirement, and when it reached 2 times HJ 350-2007B, Pb leaching concentration exceeded, three times of the B standard, three kinds of Pb, As and Cd are all unable to meetthe leaching standard. The exogenous heavy metal mainly existed in the high activity forms after it entered the soil. After treated, the activity forms decreased while the residual state increased.
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Key words:
- geopolymer /
- composite pollution /
- purple soil /
- soil remediation /
- leaching toxicity /
- stable efficiency /
- morphological analysis
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