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Solidification/Stabilization of Pb2+ and Cd2+ Contaminated Soil Using Fly Ash and GGBS Based Geopolymer
Arabian Journal for Science and Engineering ( IF 2.6 ) Pub Date : 2021-08-26 , DOI: 10.1007/s13369-021-06109-1
Hairong Wang 1 , Zhiduo Zhu 1 , Shaoyun Pu 1 , Weilong Song 1
Affiliation  

Geopolymer is an environment-friendly cementitious material, which can effectively immobilize heavy metals. However, the existing study on solidification/stabilization (S/S) of heavy metal contaminated soil using geopolymer is very limited. In order to investigate the effects of geopolymer produced by activating fly ash (FA) and ground granulated blast-furnace slag (GGBS) (FA + GGBS) with composite activator of Na2SiO3 and NaOH on environmental and engineering properties of Pb2+ and Cd2+ contaminated soil, a series of tests including soil pH, leachate pH and electrical conductivity (EC), toxicity leaching, UCS and pH-dependent tests were conducted at different curing times. Additionally, scanning electron microscopy/energy dispersive spectroscope (SEM/EDS), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests were performed to analyze the micro mechanism of FA + GGBS based geopolymer solidified contaminated soil. The results indicated that the UCS and pH of soil increased steadily with FA + GGBS content and curing time increasing. Moreover, as FA + GGBS content and curing time increased, the leached Pb2+, Cd2+ concentration decreased significantly, and the concentration was closely related to the pH of leachate. Compared with Cd2+, the solidification ratio of FA + GGBS based geopolymer for Pb2+ was lower. Besides, the leached Pb2+ and Cd2+ concentrations decreased first and then increased with increasing pH of extraction fluid. Microscopic analysis showed that the gel products of FA + GGBS based geopolymer were mainly C-(N)-A-S–H gels. However, the geopolymer structure became looser due to the existence of Pb2+ or Cd2+. The formation of Cd(OH)2 was the primary solidification mechanism of Cd2+, while Pb2+ was mainly immobilized in geopolymer structure by ion exchange. The MIP results showed that the volume of inter-aggregate pores between 0.01 and 1 μm reduced with increasing FA + GGBS content of solidified soil.



中文翻译:

使用粉煤灰和 GGBS 基地质聚合物固化/稳定 Pb2+ 和 Cd2+ 污染土壤

地聚合物是一种环保胶凝材料,可有效固定重金属。然而,现有的利用地质聚合物对重金属污染土壤进行固化/稳定(S/S)的研究非常有限。为了研究用Na 2 SiO 3和NaOH复合活化剂活化粉煤灰(FA) 和磨碎的高炉矿渣(GGBS) (FA + GGBS) 生产的地质聚合物对Pb 2+ 的环境和工程性能的影响和镉2+针对受污染土壤,在不同的固化时间进行了一系列测试,包括土壤 pH 值、渗滤液 pH 值和电导率(EC)、毒性浸出、UCS 和 pH 依赖性测试。此外,还进行了扫描电子显微镜/能谱仪(SEM/EDS)、X射线衍射(XRD)和压汞孔隙率(MIP)测试,分析了基于FA+GGBS的地质聚合物固化污染土壤的微观机理。结果表明,随着FA+GGBS含量和固化时间的增加,土壤UCS和pH值稳步上升。此外,随着FA+GGBS含量和固化时间的增加,浸出的Pb 2+、Cd 2+浓度显着降低,且该浓度与浸出液的pH值密切相关。与 Cd 2+相比, FA + GGBS 基地质聚合物对 Pb 2+的凝固率较低。此外,浸出的Pb 2+和Cd 2+浓度随着萃取液pH值的增加而先降低后升高。显微分析表明,FA+GGBS基地质聚合物的凝胶产物主要是C-(N)-AS-H凝胶。然而,由于Pb 2+或Cd 2+的存在,地质聚合物结构变得松散。Cd(OH) 2的形成是 Cd 2+的主要凝固机制,而 Pb 2+主要通过离子交换固定在地质聚合物结构中。MIP 结果表明,随着固化土壤中 FA + GGBS 含量的增加,0.01 到 1 μm 之间的团聚体孔隙体积减小。

更新日期:2021-08-27
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