Badreddine R, Humez A N, Mingelgrin U, Benchara A, Meducin F, Prost R
Unité de Science du sol, INRA, Route de Saint Cyr, 78026 Versailles, France.
Environ Sci Technol. 2004 Mar 1;38(5):1383-98. doi: 10.1021/es0209520.
Toxic elements found in wastes may have a negative impact on the environment, especially through the contamination of groundwater and plants. To reduce their mobility and availability, French regulations mandate the solidification and stabilization of toxic wastes. Many methods to stabilize and solidify wastes exist, among them the Ecofix process which employs low cost materials and consists of mixing wastes with lime, aluminum hydroxide, and silica. To evaluate the long-term behavior of solidified/stabilized (S/S) samples, their alteration under saturated conditions was studied in a water extractor, a Soxhlet-like device, used to follow the weathering of rocks. Kinetic measurements have shown that the release of Fe, Pb, Cd, Cr, and Cu was very slow, indicating a strong retention of these elements by the S/S materials prepared by the Ecofix process. To elucidate the mechanisms of retention of the trace metals, the mineral phases that existed in the S/S samples throughout and at the end of the extraction runs were studied by X-ray diffraction and by infrared and nuclear magnetic resonance spectroscopies. Scanning electron microscopic (SEM) examinations and electron microprobe analyses of the S/S samples were also performed at different stages of weathering. These observations revealed that assorted calcium silicate hydrates (C-S-H) were the predominant phases in the S/S preparations and that gradual alterations occurred in the structure of the investigated materials. The overall Ca/Si ratio of the C-S-H phases decreased as the enhanced alteration progressed. Although trace metals in oxide, hydroxide, and carbonate forms were found in the S/S materials, the bulk of the trace metals was incorporated in the matrix of the C-S-H phases.
废弃物中发现的有毒元素可能会对环境产生负面影响，尤其是通过污染地下水和植物。为降低其迁移性和有效性，法国法规要求对有毒废弃物进行固化和稳定化处理。存在多种稳定化和固化废弃物的方法，其中包括Ecofix工艺，该工艺使用低成本材料，是将废弃物与石灰、氢氧化铝和二氧化硅混合。为评估固化/稳定化（S/S）样品的长期性能，在一种类似索氏提取器的水提取装置中研究了它们在饱和条件下的变化情况，该装置用于跟踪岩石的风化过程。动力学测量表明，铁、铅、镉、铬和铜的释放非常缓慢，这表明通过Ecofix工艺制备的S/S材料对这些元素具有很强的保留能力。为阐明痕量金属的保留机制，通过X射线衍射、红外光谱和核磁共振光谱研究了在整个提取过程及提取结束时S/S样品中存在的矿物相。还在风化的不同阶段对S/S样品进行了扫描电子显微镜（SEM）检查和电子微探针分析。这些观察结果表明，各种硅酸钙水合物（C-S-H）是S/S制剂中的主要相，并且所研究材料的结构发生了逐渐变化。随着蚀变程度的加深，C-S-H相的总体钙硅比降低。尽管在S/S材料中发现了氧化物、氢氧化物和碳酸盐形式的痕量金属，但大部分痕量金属都结合在了C-S-H相的基质中。
