pH impact on reductive dechlorination of cis-dichloroethylene by Fe precipitates: an X-ray absorption spectroscopy study.
The pH impact on reductive dechlorination of cis-dichloroethylene (cis-DCE) was investigated using in situ Fe precipitates formed under iron-rich sulfate-reducing conditions. The dechlorination rate of cis-DCE increased with pH, which was attributed to changes in the solid-phase Fe concentration, the composition of Fe minerals, and the surface speciation of Fe minerals. With increasing pH, larger quantities of Fe minerals, having much greater reactivity than dissolved Fe(II), were produced. Fe-K edge X-ray absorption spectroscopy (XAS) analysis of Fe precipitates revealed the presence of multiple Fe phases with their composition varying with pH. Correlation analyses were performed to examine how the solid-phase Fe concentration, the composition of Fe minerals, and their surface speciation were linked with the cis-DCE dechlorination rate. Such analyses revealed that neither mackinawite (FeS) nor magnetite (Fe3O4) was reactive with cis-DCE dechlorination, but that Fe (oxyhydr)oxides including green rusts and Fe(OH)2 were reactive. Based on a proposed model of the surface acidity of Fe minerals, the increasing deprotonated surface Fe(II) groups with pH correlated well with the enhanced cis-DCE dechlorination.
Department of Geological Sciences, Pusan National University, Busan 609-735, Republic of Korea. Electronic address: hjeong@pusan.ac.kr.
Hoon Y
HY
Jeong
Karthik
K
Anantharaman
Sung P
SP
Hyun
Moon
M
Son
Kim F
KF
Hayes
D011232:Chemical Precipitation; D004000:Dichloroethylenes / Q000737:chemistry*; D004777:Environment; D054879:Halogenation; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D016018:Least-Squares Analysis; D016014:Linear Models; D010084:Oxidation-Reduction; D056928:X-Ray Absorption Spectroscopy
D004000:Dichloroethylenes; D007501:Iron
EXAFS; Green rust; Mackinawite; Magnetite; Reductive dechlorination; cis-DCE