Abstract
Ettringite is commonly used for the stabilization/solidification for heavy metal‐contaminated soils, and its treatment effect will be influenced by Ca/Al mole ratio. Lead‐contaminated soil samples were solidified using ettringite with different Ca/Al mole ratios. The pH value, unconfined compressive strength of solidified samples, and leaching concentration were investigated to understand the influence of Ca/Al mole ratio on properties of ettringite‐solidified contaminated soils. The microstructural characteristics of solidified contaminated soils were also explored. The results show that lead leaching concentration decreases dramatically with increasing the content of lime and curing time. Lead concentration drops from 49.89 mg/L to 0.19 mg/L when Ca/Al mole ratio increases from 4 : 3 to 10 : 3 at 28 days and from 36.57 mg/L to near 0 mg/L at 90 days. In addition, the unconfined compressive strength of samples drops at first and then increases with the increase of Ca/Al mole ratio. Besides, the pH values of solidified soil and leachate rise with the increase of content of lime. The pH values of solidified soil increase from 9.68 to 11.34, and there is little difference between 28 days and 90 days. However, the pH values of leachate increase from 5.56 to 8.59 at 28 days, and 90‐day pH values increase from 5.65 to 9.44. The results of SEM, XRD, and EDS tests also indicate that Ca/Al mole ratio affects the shape of ettringite, the stabilization/solidification effectiveness of contaminated soil, and the pore of solidified soil. When Ca/Al mole ratio equals to 8 : 3, ettringite content has a substantial increase, and lead leaching concentration is lower than 5 mg/L.
Highlights
Heavy metal-contaminated soils have attracted much attention from engineers and environmentalists during the past decades for it may cause significant damages on human health and ecosystem [1]. ere are many techniques that can be used to reduce the bad effect of heavy metal-contaminated soils, among which solidification/stabilization is seen as a common way [2,3,4,5] with its economic advantage and effectiveness
In order to clarify the effect of Ca/Al mole ratio on the stabilization and immobilization of heavy metal lead by ettringite, this study investigated the physical, mechanical, and leaching performances of solidified soil with different Ca/Al mole ratios. e binder consisted of high-alumina cement, lime, and gypsum and remained the total content of 15% through experiments, and the S/Al mole ratio kept unchanged
By means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP), this study investigated the microcosmic mechanism that the Ca/Al mole ratio affects the leaching and mechanical performances of solidification/immobilization of heavy metalcontaminated soil by ettringite. e results revealed that the variation of Ca/Al mole ratio in ettringite has significant influences on its performance when solidifying/ stabilizing lead-contaminated soils
Summary
Heavy metal-contaminated soils have attracted much attention from engineers and environmentalists during the past decades for it may cause significant damages on human health and ecosystem [1]. ere are many techniques that can be used to reduce the bad effect of heavy metal-contaminated soils, among which solidification/stabilization is seen as a common way [2,3,4,5] with its economic advantage and effectiveness. Many studies indicated that the solidification/ stabilization of contaminated soils with ettringite may be Advances in Civil Engineering affected by the concentration of certain ions. In order to clarify the effect of Ca/Al mole ratio on the stabilization and immobilization of heavy metal lead by ettringite, this study investigated the physical, mechanical, and leaching performances of solidified soil with different Ca/Al mole ratios. By means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP), this study investigated the microcosmic mechanism that the Ca/Al mole ratio affects the leaching and mechanical performances of solidification/immobilization of heavy metalcontaminated soil by ettringite. E results revealed that the variation of Ca/Al mole ratio in ettringite has significant influences on its performance when solidifying/ stabilizing lead-contaminated soils By means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP), this study investigated the microcosmic mechanism that the Ca/Al mole ratio affects the leaching and mechanical performances of solidification/immobilization of heavy metalcontaminated soil by ettringite. e results revealed that the variation of Ca/Al mole ratio in ettringite has significant influences on its performance when solidifying/ stabilizing lead-contaminated soils
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