The reductive dechlorination of CCl{sub}4 and CHCl{sub}3 in the presence of the synthetic sulfate form of green rust (GR{sub}(SO{sub}4), Fe{sub}4{sup}IIFe {sub}2{sup}III(OH){sub}12SO{sub}4yH{sub}2O, at pH～8 and room temperature was investigated.Reduction of CCl{sub}4 produces CHCl{sub}3 and C{sub}2Cl{sub}6 as main chloroaliphatic products, while GR{sub}(SO{sub}4) is oxidized to magnetite (Fe{sub}3O{sub}4). The formation of C{sub}2Cl{sub}6 indicates a coupling reaction between trichloromethylradicals in the suspension. Chloroform was much less susceptible than CCl{sub}4 to reductive dechlorination by GR{sub}(SO{sub}4) showing reduction rates approximately 100 times less than for reduction of CCl{sub}4. The transformation of CCl{sub}4 byGR{sub}(SO{sub}4) can be described by pseudo-first-order reaction kinetics with respect to formation of chloride. At room temperature the rate expression is given as: dCl{sub}-/dt≌ -dCCl{sub}4/dt= r·k{sub}(obs)Fe(II){sub}(GR), where k{sub}(obs) is in the range (0.47×10{sup}-5)-(2.18×10{sub}-5) s{sub}-1 for CCl{sub}4 concentrations above its aqueous solubility. This narrow range may be due to the constant CCl{sub}4(aq) concentration owing to buffering of the CCl{sub}4(aq) concentration by freephase CCl{sub}4(I) thereby indicating that the reaction takes place in solution. Experiments with initial CCl{sub}4 concentrations below its aqueous solubility support this theory. The reaction kinetics are compared with similar reactions where iron(0) is used as reductant of CCl{sub}4. The first-order rate constants for transformation of CCl{sub}4 with zerovalent iron and GR{sub}(SO{sub}4), respectively, are found to be in the same range. Thus, GRs formed during corrosion of iron(0) under nonacidconditions may considerably contribute to the total reduction of CCl{sub}4 measured in iron(0) systems.
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