Reductive transformation of carbon tetrachloride by sulfide-treated goethite

In natural environments, many reductants contribute to the reductive transformation of chlorinated aliphatic hydrocarbons (CAHs). To effectively apply monitored natural attenuation in the remediation of CAH-contaminated aquifers, the identification of the predominant species that determine the reaction rate and the parameters that control the product distribution is needed. In this research, sulfide (S(-II))-treated goethite was used to simulate sulfate-reducing iron oxide-rich environments and the reductive dechlorination of carbon tetrachloride (CT) was studied. By changing pH and added Fe(II) and, by aging, the abundance of different reductants in S(-II)-treated goethite was changed in order to correlate the concentration of the different reductants with CT reduction rates. Experimental results indicated that weakly bound Fe(II) is the most reactive species in the electron transfer from surface to CT. Formate, CS₂, CO and chloroform were identified as CT transformation products in S(-II)-treated goethite. A chlorine balance showed that the unidentified products were completely dechlorinated.