| Title |
Influence of Temperature on the Treatment Efficiency of Chlorinated Organic Substances in Groundwater by Permeable Reactive Barrier |
| Authors |
김선혜 ( Sun Hye Kim ) ; 김은지 ( Eun Zi Kim ) ; 김동수 ( Dong Su Kim ) |
| DOI |
https://doi.org/10.15681/KSWE.2014.30.2.175 |
| Keywords |
Chlorinated organic substance; Groundwater; Permeable reactive barrier; Pourbaix diagram; Temperature |
| Abstract |
The influence of temperature on the treatment efficiency of chlorinated organic substances contained in groundwater by permeable reactive barrier which is composed of Feo has been investigated by constructing the Pourbaix diagrams for Fe-H2O system at different temperatures based on thermodynamic estimation. In aerobic condition, the equilibrium potentials for Feo/Fe2+ and Fe2+/Fe3+ were observed to increase, therefore, the dechlorination reaction for organic pollutants by Feo was considered to decline with temperature due to the diminished oxidation of reactive barrier. The result for the variations of the ionization fraction of Fe2+ and Fe3+ ion in the pH range of 0 ~ 2.5 obtained by employing Visual MINTEQ program showed that the ionization fraction of Fe2+ increased with pH, however, that of Fe3+ decreased symmetrically and the extent of the variation of ionization fraction for both ions was raised as temperature rises. The equilibrium pH for Fe3+/Fe(OH)3 was examined to decrease with temperature so that the treatment efficiency of chlorinated organic substance was expected to decrease with temperature due to the enhanced formation of passivating film in aerobic condition. The change of the reactivity of a specific chemical species with temperature was defined quantitatively based on the area of its stable region in Pourbaix diagram and depending on this the reactivity of Fe3+ was shown to decrease with temperature, however, that of Fe(OH)3 was decreased monotonously as temperature is raised for Fe3+/Fe(OH)3 equilibrium system. In anaerobic condition, the equilibrium potential for Feo/Fe2+ was observed to rise and the equilibrium pH for Fe2+/Fe(OH)2 were examined to decrease as temperature increases, therefore, similar to that for aerobic condition the efficiency of the dechlorination reaction for organic substances was considered to be diminished when temperature rises because of the reduced oxidation of Feo and increased formation of Fe(OH)2 passivating film. |