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Identification of Active Agents for Reductive Dechlorination Reactions in Cement/Fe (II) Systems by Using Cement Components  

Jeong, Yu-Yeon (Department of Environmental Engineering, Pusan National University)
Kim, Hong-Seok (Department of Environmental Engineering, Pusan National University)
Hwang, In-Seong (Department of Environmental Engineering, Pusan National University)
Publication Information
Journal of Soil and Groundwater Environment / v.13, no.1, 2008 , pp. 92-100 More about this Journal
Abstract
Experimental studies were conducted to identify the active agents for reductive dechlorination of TCE in cement/Fe(II) systems focusing on cement components such as CaO, $Fe_2O_3$, and $Al_2O_3$. A hematite that was used to simulate an $Fe_2O_3$ component in cement was found to have degradation efficiencies (k = 0.641 $day^{-1}$) equivalent to that of cement/Fe(II) systems in the presence of CaO/Fe(II), only when it contained an aluminum impurity$(Al_2O_3)$. When the effect of $Al_2O_3$ content of hematite/CaO/$Al_2O_3$/Fe(II) system was tested, the mole ratio of $Al_2O_3$ to CaO affected the rate of TCE degradation with an optimum ratio around 1 : 10 that resulted in a rate constant of 0.895 $day^{-1}$. In the SEM images of hematite/CaO/$Al_2O_3$/Fe(II) systems, acicular crystals were also found that were also observed in cement/Fe(II) systems. Thus it was suspected that these crystals were reactive reductants and that they might be goethite or ettringite that are known to have acicular structures. An EDS element map analysis revealed that these crystals were not goethite crystals. A subsequent experiment that tested reactivities of compounds formed during the ettringite synthesis showed that ettringite and minerals associated with ettringite formation are not reactive reductants. These observations conclude that a mineral containing CaO and $Al_2O_3$ with a acicular structure could be a major reactive reductant of cement/Fe(II) systems.
Keywords
Reductive dechlorination; Hematite; Calcium oxide(CaO); Aluminium oxide($Al_2O_3$; ); TCE; Acicular crystal;
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Times Cited By KSCI : 1  (Citation Analysis)
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