| Summary: | 碩士 === 國立清華大學 === 生醫工程與環境科學系 === 95 === The dechlorination of carbon tetrachloride (CT) by biogenic iron species produced from the reductive dissolution of ferrihydrite by Geobacter sulfurreducens in aqueous solutions containing quinone compounds as electron mediators was investigated. The use of quinone compounds in the presence of G. sulfurreducens under iron-reductive conditions can effectively dechlorinate CT. The dechlorination of CT followed pseudo-first-order kinetics and the pseudo-first-order constants (kobs) for 10 �嵱 AQDS, LQ (lawson) and NQ (naphthoquinone) were correspond to 6.5, 5.1, and 2.5 times higher than that in control systems, respectively. The dechlorination of CT was related to the ferrous concentrations produced from the dissolution of ferrihydrite by G. sulfurreducens. The dechlorination of CT was obvious when the system amended with 100 �嵱 quinone compounds and contained no ferrihydrite in the presence of G. sulfurreducens under anaerobic conditions. Addition of ferrihydrite enhanced the efficiency and rate of CT dechlorination under iron-reducing conditions. This enhanced effect is attributed to the formation of active surface-bound iron species when ferrous adsorbed onto the surface of ferric oxides. In addition, the amendment of 10 �嵱 AQDS, LQ, or NQ produced the highest Fe(II) concentration in the presence of G. sulfurreducens. Addition of 0.2 mM NQ and BQ into media, however, inhibited the growth of G. sulfurreducens. Spectroscopic results including EPR and UV-Vis showed that the selected quinone compounds can form various active electron mediators for electron transfer. AQDS can be reduced to semiquinone, LQ can be converted to hydroquinone, while NQ could be produced to hydroquinone and trace amounts of semiquinone in the presence of G. sulfurreducens. Results obtained show that addition of quinone compounds can enhance the ferrous production, and subsequently formed surface-bound iron species to effectively dechlorinate chlorinated hydrocarbon for long-term remediation under iron-reducing conditions.
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