Microstructural Evaluation of Stabilization and Solidification of Heavy Metals by Cement at the Presence of Nano Montmorillonite

Stabilization/Solidification (S/S) is an attractive technology which helps to reduce the toxicity and facilitate the disposal of sediments containing heavy metals, industrial wastes, and contaminated soils. The efficiency of the S/S technology can be enhanced by the use of clay nanoparticles. The S/S process incorporating Montmorillonite nanoparticles can be employed to prevent the dissemination of heavy metals effectively. Although many studies have addressed the stabilization of contaminant by the use of cement, few have discussed the microstructural interactions between montmorillonite nanoparticles, heavy-metal contaminants, and cement in different time intervals. In addition, there are not enough researches on the impact of montmorillonite nanoparticles in the efficiency of solidification process. Therefore, this study aims to investigate the interactions between montmorillonite nanoparticles, heavy metals, and cement in different time intervals from microstructural point of view and to determine the impact of clay nanoparticles on toxicity leaching from solidified/stabilized contaminants. To achieve the above mentioned objectives, different concentrations of heavy metal (zinc) and different percentages of Portland cement were added to nano-montmorillonite. The contaminant retention mechanism was then experimentally analyzed through monitoring the changes in pH, evaluating microstructural changes (using X-Ray Diffraction), and Toxicity Characteristic Leaching Procedure (TCLP) measurement. The results indicate the role of clay nanoparticles in retaining the heavy-metal contaminant and the lack of linear relation between the quantity of cement content of the specimen and the contaminant retention efficiency.