水泥基复合固化剂对镉和锌混合污染土的固化试验研究

Utilization of Cement-Based Composite Curing Agent for Solidification/Stabilization of Soil Contaminated by Dual Ionic Cd2+ and Zn2+

摘要:

为了研究水泥基复合固化剂对重金属混合污染土的固化稳定效果及其与单一重金属污染土的固化效果差别，探究锌和镉离子之间是否有协同或拮抗作用，采用水泥、石灰、粉煤灰和蒙脱石等作为复合固化剂，通过开展无侧限抗压强度试验、毒性浸出试验、X射线衍射分析（XRD）以及电镜扫描分析（SEM），研究锌镉混合污染土在不同固化剂掺量下的强度特性与浸出毒性、pH值与浸出毒性间的关系、重金属混合污染土与单一重金属污染土的固化效果差异，并通过XRD和SEM分别对固化产物的成分和形貌进行微观分析，进而分析固化机理。试验结果表明：用生石灰、粉煤灰、海泡石、蒙脱土替代等量水泥可使固化产物的强度提高；Zn²⁺与Cd²⁺之间不存在拮抗作用，Cd²⁺的存在还会有助于Zn²⁺的固定；重金属离子的浸出浓度随浸出液pH值的增大而明显降低；固化效果好的样品相较于固化效果差的样品有更多的针状、网状等较为致密的结构。

Abstract:

This paper aims to study the solidification and stabilization effect of cement-based composite cement curing agent on mixed contaminated soil with a high level of Cd and Zn， to explore whether there is synergy or antagonism between Zn and Cd， and to Compare the difference of curing effect between mixed contaminated soil and single contaminated soil. The cement-based composite cement curing agent includes cement， lime， fly ash， and montmorillonite. Four tests including the unconfined compressive strength test， the toxic leaching test， the X-ray diffraction（XRD） analysis ，and scanning electron microscope（SEM） test were performed. These tests can study mixed contaminated soil strength characteristics and leaching toxicity at different curing agent contents. In addition，this paper also investigats the relationship between the pH value and leaching toxicity and the solidification difference between the mixed contaminated soil and the single contaminated soil Moreover， it analyzes the composition and morphology of the solidified products by XRD and SEM， and then analyzes curing mechanism. The results prove that the strength of solidified products can be improved by using quicklime， fly ash， sepiolite， and montmorillonite instead of the same amount of cement. There is no antagonism between Zn²⁺ and Cd²⁺， and the existence of Cd²⁺ can help the fixation of Zn²⁺. The leaching concentration of heavy metal ions decreases significantly with the increase of leaching solution pH value. Compared with the samples with poor curing effect， the samples with good curing effect have more acicular， reticular， and other relatively dense structures.