Journal article
Chlorinated solvent transformation by palladized zerovalent iron: mechanistic insights from reductant loading studies and solvent kinetic isotope effects
Environmental science & technology, Vol.47(14), pp.7940-7948
07/16/2013
DOI: 10.1021/es401481a
PMID: 23755912
Abstract
Palladized nanoscale zerovalent iron (Pd/NZVI) has been utilized for source zone control, yet the reductant responsible for pollutant transformation and the optimal conditions for subsurface application remain poorly understood. Here, trends in Pd/Fe reactivity toward 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and cis-dichloroethene (cis-DCE) were compared in H2O and D2O batch systems as a function of pH, chlorinated solvent concentration, Pd surface loading, Pd/Fe mass loading, Pd/Fe aging time, and zerovalent iron [Fe(0)] particle size. For Pd/NZVI, the solvent kinetic isotope effect [i.e., kobs(H2O)/kobs(D2O) or SKIE] for 1,1,1,2-TeCA and cis-DCE reduction increased substantially with Pd loading and Pd/NZVI concentration, evidence that multiple pathways exist for chlorinated solvent reduction. At low Pd loadings and Pd/NZVI concentrations with relatively small SKIEs (less than ~5), we propose that modest reactivity enhancements (≤ 10-fold) reflect more efficient electron transfer to 1,1,1,2-TeCA from Fe(0) facilitated by Pd nanodeposits. Much larger SKIEs (e.g., exceeding 100 for cis-DCE) imply the involvement of atomic hydrogen in more reactive systems with high Pd loadings and Pd/NZVI concentrations. Generally, evidence of SKIEs supporting a dominant role for atomic hydrogen was not observed for Pd/Fe prepared from micrometer-sized Fe(0), or for any size of nonpalladized Fe(0). During anaerobic aging of Pd/NZVI, decreases in the SKIE for 1,1,1,2-TeCA reduction suggest that atomic hydrogen will contribute to reactivity for only approximately 1 week after application.
Details
- Title: Subtitle
- Chlorinated solvent transformation by palladized zerovalent iron: mechanistic insights from reductant loading studies and solvent kinetic isotope effects
- Creators
- Yang Xie - Department of Chemical and Environmental Engineering, University of California , A242 Bourns Hall, Riverside, California 92521, USADavid M Cwiertny
- Resource Type
- Journal article
- Publication Details
- Environmental science & technology, Vol.47(14), pp.7940-7948
- Publisher
- United States
- DOI
- 10.1021/es401481a
- PMID
- 23755912
- ISSN
- 0013-936X
- eISSN
- 1520-5851
- Grant note
- P30 ES005605 / NIEHS NIH HHS
- Language
- English
- Date published
- 07/16/2013
- Academic Unit
- Center for Health Effects of Environmental Contamination; Civil and Environmental Engineering; Public Policy Center (Archive); Chemical and Biochemical Engineering
- Record Identifier
- 9983991938402771
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