Journal article
Influence of anionic cosolutes and pH on nanoscale zerovalent iron longevity: time scales and mechanisms of reactivity loss toward 1,1,1,2-tetrachloroethane and Cr(VI)
Environmental science & technology, Vol.46(15), pp.8365-8373
08/07/2012
DOI: 10.1021/es301753u
PMID: 22780331
Abstract
Nanoscale zerovalent iron (NZVI) was aged over 30 days in suspension (2 g/L) with different anions (chloride, perchlorate, sulfate, carbonate, nitrate), anion concentrations (5, 25, 100 mN), and pH (7, 8). During aging, suspension samples were reacted periodically with 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA) and Cr(VI) to determine the time scales and primary mode of NZVI reactivity loss. Rate constants for 1,1,1,2-TeCA reduction in Cl(-), SO(4)(2-), and ClO(4)(-) suspensions decreased by 95% over 1 month but were generally equivalent to one another, invariant of concentration and independent of pH. In contrast, longevity toward 1,1,1,2-TeCA depended upon NO(3)(-) and HCO(3)(-) concentration, with complete reactivity loss over 1 and 14 days, respectively, in 25 mN suspensions. X-ray diffraction suggests that reactivity loss toward 1,1,1,2-TeCA in most systems results from Fe(0) conversion into magnetite, whereas iron carbonate hydroxide formation limits reactivity in HCO(3)(-) suspensions. Markedly different trends in Cr(VI) removal capacity (mg Cr/g NZVI) were observed during aging, typically exhibiting greater longevity and a pronounced pH-dependence. Notably, a strong linear correlation exists between Cr(VI) removal capacities and rates of Fe(II) production measured in the absence of Cr(VI). While Fe(0) availability dictates longevity toward 1,1,1,2-TeCA, this correlation suggests surface-associated Fe(II) species are primarily responsible for Cr(VI) reduction.
Details
- Title: Subtitle
- Influence of anionic cosolutes and pH on nanoscale zerovalent iron longevity: time scales and mechanisms of reactivity loss toward 1,1,1,2-tetrachloroethane and Cr(VI)
- Creators
- Yang Xie - Department of Chemical and Environmental Engineering, University of California , Riverside A242 Bourns Hall Riverside, California 92521, USADavid M Cwiertny
- Resource Type
- Journal article
- Publication Details
- Environmental science & technology, Vol.46(15), pp.8365-8373
- Publisher
- United States
- DOI
- 10.1021/es301753u
- PMID
- 22780331
- ISSN
- 0013-936X
- eISSN
- 1520-5851
- Language
- English
- Date published
- 08/07/2012
- Academic Unit
- Center for Health Effects of Environmental Contamination; Civil and Environmental Engineering; Public Policy Center (Archive); Chemical and Biochemical Engineering
- Record Identifier
- 9983992091202771
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