Investigating the Dissolution Behaviour and Dental Amalgam immobilization in Different Geopolymer Cement Waste Form

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Dental amalgam is composed of mercury alloy, where the mercury is the major component. The dental amalgam usage has brought the global attention as it has an environmental and health hazard, which are covered in this dissertation. This project backed up with statistics compiled from different literatures as it interprets the issue in numbers, which gives the problematic material (dental amalgam (mercury)) a priority attention as it has mercury. There are different sources where mercury released whether naturally or industrially, and the random disposal of the dental amalgam (mercury) just exacerbate the situation. Therefore, this project supporting the treatment of the wastewater loaded with toxic metals in the aspect of investigating the Mercury immobilization using geopolymer cementitious material. The aim of this project is to investigate the potential of the mercury immobilization in geopolymer wasteform as the ordinary Portland cement has low durability and immobilization efficiency in comparison with geopolymers. Thus, different recovery process for dental amalgam mercury from domestic wastewater were reviewed and the focus in this project was on the ion exchange process as a recovery technique. Furthermore, Different cementitious materials were investigated in terms of their properties and more focus was on the geopolymer cement wasteform. The aim of this chapter is to provide a scientific benchmark for the materials and methods that would be used for conducting this project, which are ion-exchange using zeolite filter for separating mercury from waste water and geopolymer cement wasteform as a binder material. However, owing to the global pandemic (rapid Covide-19 outbreak), all face to face learning and lab work were suspended then paused to unknown time, which affected the plan of this work and added some limitation and challenges to the flow and quality of this project. Therefore, the data acquisition method alternated to be obtained via data mining method, where the sources studying mercury immobilization in geopolymer are limited, so a further challenge affected the plan and the progress of the project. The methodology of the project was based on data mining, searching about the dissolution behaviour of geopolymers under different conditions in the past studies, collecting data about the factors affect the mechanical properties and the possibility of mercury immobilization in geopolymers. All the studies utilized in this project were filtered and verified, then the data extracted and analysed. There are some patterns were observed, and findings that comply with other studies which are Si and Al solubility are influenced by the change of temperature and alkaline concentration, which reflect positively on the geopolymerization process. Moreover, it is noticed that the increase in curing temperature, curing and aging duration can affect the geopolymer durability and immobilization efficiency. Finally, based on the data obtained and analysed, geopolymers have the capacity to immobilize recovered mercury by 98 to 99% at optimum curing temperatures between 25 C to 85 C, yet the more Hg-concentration the more leaching observed. It is recommended that further studies with regard to mercury immobilization in geopolymer wasteform should be conducted and investigated under different conditions.
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