Abstract
Chlorinated ethenes have been used extensively as solvents, degreasers, and dry-cleaning agents in a range of commercial and industrial applications. This has created a legacy of contaminated soils and groundwater, particularly with respect to perchloroethylene (PCE; a.k.a. tetrachloroethene—C2Cl4), and trichloroethylene (TCE; a.k.a. trichloroethene—C2HCl3), prompting the development of a wide array of treatment technologies for remediation of chlorinated ethene-contaminated environments. Green rusts are highly redox-active layered Fe(II)-Fe(III) hydroxides that have been shown to be facile reductants for a wide range of organic and inorganic pollutants. The reduction of chlorinated ethenes [vinyl chloride (VC); 1,1-dichloroethene(11DCE), cis-1,2-dichloroethene (c12DCE), trans-1,2-dichloroethene (t12DCE), TCE, and PCE] was examined in aqueous suspensions of green rust, alone as well as with the addition of Ag(I) (AgGR) or Cu(II) (CuGR). Green rust alone was ineffective as a reductant for the reductive dechlorination for all of the chlorinated ethenes. Near-complete removal of PCE was observed in the presence of AgGR, but all other chlorinated ethenes were essentially non-reactive. Partial removal of chlorinated ethenes was observed in the presence of CuGR, particularly 11DCE (34%), t12DCE (51%), and VC (66%). Significant differences were observed in the product distributions of chlorinated ethene reduction by AgGR and CuGR. The effectiveness of Ag(I)- and Cu(II)-amended green rusts for removal of chlorinated ethenes may be improved under different conditions (e.g., pH and interlayer anion) and warrants further investigation.
Highlights
Ag(I)- and Cu(II)-amended green rusts for removal of chlorinated ethenes may be improved under different conditions and warrants further investigation
To acetylene (>85%) [78]; no reduction was observed in the presence of either bone char or green rust alone. These results show that modified or amended green rust may be effective agents for the reductive dechlorination of chlorinated hydrocarbons including chlorinated ethenes
Sulfate green rust was synthesized by air oxidation of a 1.0 M Fe(II)SO4 solution as described by O’Loughlin et al [83]
Summary
Green rusts are key components of the biogeochemical cycling of Fe in aquatic and terrestrial systems and are formed during microbial reduction of Fe(III) oxides [2,3,4,5,6,7,8,9,10,11,12], during direct microbial or coupled biotic/abiotic oxidation of Fe(II) under anoxic conditions by denitrifying bacteria [13,14,15,16], and during abiotic and microbially induced corrosion of iron and steel [17,18,19,20] As such, they are found in Fe(II)–Fe(III) transition zones in a variety of natural and engineered environments including surface waters [21], groundwater [22,23], soils [24,25,26,27,28,29], sediments [30,31,32], and permeable reactive barriers [33,34,35,36,37,38], often as the minerals fougérite, trébeurdenite, and mössbauerite [39,40,41]. Their use in a range of commercial and industrial applications, as well as from improper disposal, has created a legacy of contaminated soils and groundwater, with respect to carbon tetrachloride (CT; a.k.a. tretrachloromethane-CCl4 ), chloroform (CF; a.k.a. trichloromethane-CHCl3 ), methylene chloride (DCM; a.k.a. dichloromethaneCH2 Cl2 ), 1,1,1-trichloroethane (111TCA; C2 H3 Cl3 ), 1,2-dichloroethane (12DCA; C2 H4 Cl2 ), perchloroethylene (PCE; a.k.a. tetrachloroethene—C2 Cl4 ), and trichloroethylene
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