Efficient Dechlorination of Carbon Tetrachloride by Hydrophobic Green Rust Intercalated with Dodecanoate Anions

Abstract

The reductive dechlorination of carbon tetrachloride (CT) by Fe(II)-Fe(III) hydroxide (green rust) intercalated with dodecanoate, Fe(II)(4)Fe(III)(2)(OH)(12)(C(12)H(23)O(2))(2) · yH(2)O (designated GR(C12)), at pH ~ 8 and at room temperature was investigated. CT at concentration levels similar to those found in heavily contaminated groundwater close to polluted industrial sites (14-988 μM) was reduced mainly to the fully dechlorinated products carbon monoxide (CO, yields >54%) and formic acid (HCOOH, yields >6%). Minor formation of chloroform (CF), the only chlorinated degradation product, was also detected (yields <6.3%). Reactions carried out with excess GR followed pseudo first-order kinetics with respect to CT with rate constants ranging from 6.5 × 10(-2) to 0.47 h(-1). These rate constants are comparable to those measured for CT dechlorinations mediated by zerovalent iron. Reduction of the highest concentration of CT (1.4 mM) proceeds until 56% of the Fe(II) sites of GR(C12) was consumed. This reaction ceased after 10 h due to surface passivation of GR(C12).

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature

“…A study also shows that 0.3% magnetite in aquifer sediment was responsible for the natural attenuation of cis-dichloroethene (cis-DCE) in a groundwater plume [395]. A recent study has reported CCl4 degradation by different minerals with the normalized rate constant in the order of Fe 0 > GR > Fe(II) sorbed goethite > magnetite [396]. Another study found the rate constants for cis-DCE degradation in the order of GR > Fe(OH)2 > mackinawite = magnetite [397].…”

Review of Abiotic Degradation of Chlorinated Solvents by Reactive Iron Minerals in Aquifers

“…The rate of CCl 4 degradation on pyrite was slower than on FeS, but still faster than the other Fe(II)‐containing minerals. Ayala‐Luis et al () summarized carbon tetrachloride degradation by different minerals with the normalized rate constant in the order of Fe(0) > green rust > Fe(II) sorbed goethite > magnetite.…”

“…As a result, abiotic reductive dechlorination by minerals has attracted considerable attention within the research community (e.g., Butler and Hayes ; Elsner et al ; Han et al ; Jeong and Hayes , ; Jeong et al ; Tratnyek et al ). Abiotic transformation of carbon tetrachloride (CT), trichloroethane (TCA), TCE, and PCE has been investigated by a number of research groups using reactive iron minerals such as pyrite, troilite, mackinawite (Butler and Hayes ; Choi et al ; Hansson et al ; Lee and Batchelor , ; Kim et al ), vivianite (Bae and Lee ), magnetite (Lee and Batchelor ), and green rusts (Ayala‐Luis et al ; Lee and Batchelor ; Liang and Butler ; O'Loughlin et al ). Additionally, several field‐related studies have provided evidence that reactive iron minerals, such as iron sulfides and magnetite, may have important contributions to the degradation of chlorinated solvents in natural and engineered systems (Butler et al ; Darlington et al , ; Davis et al ; Devlin and Muller ; Ferrey et al ; Kennedy et al ; Kenneke and Weber 2003; Shen and Wilson ).…”

Effects of nitrate on the treatment of lead contaminated groundwater by nanoscale zerovalent iron

“…In addition, a large amount of green rust (GR) (color of the mixture was green, and confirmed via XRD; see Fig. S2) was formed at the end of the first phase due to the formation of highly reactive Fe(II)-Fe(III) layered double hydroxides [42]. In the second phase, nitrite (formed in the first phase) was rapidly reduced by Fe 0 (in excess Fe 0 condition) or dissolved Fe 2+ .…”