Microstructural Evaluation of Progress of Lime Pozzolanic Reactions in Stabilization and Solidification of Zn Contaminant

Subject Areas : Heavy metal

Vahidreza Ouhadi ¹ (Prof., Bu-Ali Sina University, Faculty of Engineering)
Mohammad Amiri ² (Assistant Professor, Hormozgan University, Faculty of Engineering)
Mohammadhassan Bagher ³ (Master Student, Bu-Ali Sina University, Faculty of Engineering)

Received: 2014-05-07 Accepted : 2014-11-12 Published : 2016-03-20

Keywords: Stabilization and Solidificati, Zn contaminant, Lime, C-S-H Nanostructure, XRD,

Abstract :

Introduction and objective: The present research aims to investigate the mechanism of clay particles - heavy metal contaminant - lime interaction process over time from a microstructural point of view. Material and method: To achieve this objective, different percentage of lime was added to a laboratory contaminated natural soil. Then, the mechanism of contaminant retention was analyzed through studying pH changes and evaluating microstructure study (XRD). Result and discussion: The results of this research show that the addition of 10% lime to the contaminated natural clay not only stabilizes the soil, but also for a sample contaminated with 250 cmol/kg-soil concentration of zinc as a heavy metal, more than 37% increase in retention observes. The XRD evaluation shows that the presence of heavy metal contaminant reduces the extent of lime-clay interaction; consequently a reduction in the formation of C-S-H and C-A-H nanostructures happens. Based on the results of XRD experiment and soil contaminant retention measurement of the treated sample with less than 6% lime, the presence of heavy metal contaminant was probably the main cause for  peak intensity reduction of clay minerals. The results of this research show that the formation of C-S-H nanostructure improves absorption characteristics due to its high specific surface area.  In addition, its formation reduces contaminant mobility through encapsulation of heavy metal ions (solidification). Moreover, the presence of heavy metal contaminant of zinc reduces C-S-H nanostructure formation, in a way that the presence of 25 cmol/kg-soil of heavy metal contaminant of zinc reduces peak intensity of C-S-H nanostructure about 90 CpS.

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