Reductive Dechlorination of Carbon Tetrachloride Using Iron(II) Iron(III) Hydroxide Sulfate (Green Rust)
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- 作者：Marianne Erbs ; Hans Christian Bruun Hansen ; and Carl Erik Olsen
- 刊名：Environmental Science & Technology
- 出版年：1999
- 出版时间：January 15, 1999
- 年：1999
- 卷：33
- 期：2
- 页码：307 - 311
- 全文大小：105K
- 年卷期：v.33,no.2(January 15, 1999)
- ISSN：1520-5851
文摘
The reductive dechlorination of CCl4 and CHCl3 in thepresence of the synthetic sulfate form of green rust (GRSO4),FeII4FeIII2(OH)12SO4yH2O, at pH ~ 8 and room temperaturewas investigated. Reduction of CCl4 produces CHCl3 and C2Cl6as main chloroaliphatic products, while GRSO4 is oxidizedto magnetite (Fe3O4). The formation of C2Cl6 indicates a couplingreaction between trichloromethyl radicals in the suspension.Chloroform was much less susceptible than CCl4 toreductive dechlorination by GRSO4 showing reduction ratesapproximately 100 times less than for reduction of CCl4.The transformation of CCl4 by GRSO4 can be described bypseudo-first-order reaction kinetics with respect to formationof chloride. At room temperature the rate expression isgiven as: d[Cl-]/dt 
-d[CCl4]/dt = r·kobs[Fe(II)]GR, wherekobs is in the range (0.47 × 10-5)-(2.18 × 10-5) s-1 forCCl4 concentrations above its aqueous solubility. This narrowrange may be due to the constant CCl4(aq) concentrationowing to buffering of the CCl4(aq) concentration by freephase CCl4(l) thereby indicating that the reaction takes placein solution. Experiments with initial CCl4 concentrationsbelow its aqueous solubility support this theory. The reactionkinetics are compared with similar reactions whereiron(0) is used as reductant of CCl4. The first-order rateconstants for transformation of CCl4 with zerovalent iron andGRSO4, respectively, are found to be in the same range.Thus, GRs formed during corrosion of iron(0) under nonacidconditions may considerably contribute to the totalreduction of CCl4 measured in iron(0) systems.
-d[CCl4]/dt = r·kobs[Fe(II)]GR, wherekobs is in the range (0.47 × 10-5)-(2.18 × 10-5) s-1 forCCl4 concentrations above its aqueous solubility. This narrowrange may be due to the constant CCl4(aq) concentrationowing to buffering of the CCl4(aq) concentration by freephase CCl4(l) thereby indicating that the reaction takes placein solution. Experiments with initial CCl4 concentrationsbelow its aqueous solubility support this theory. The reactionkinetics are compared with similar reactions whereiron(0) is used as reductant of CCl4. The first-order rateconstants for transformation of CCl4 with zerovalent iron andGRSO4, respectively, are found to be in the same range.Thus, GRs formed during corrosion of iron(0) under nonacidconditions may considerably contribute to the totalreduction of CCl4 measured in iron(0) systems.