Sulfidation of Zero-Valent Iron by Direct Reaction with Elemental Sulfur in Water: Efficiencies, Mechanism, and Dechlorination of Trichloroethylene

Sulfidation can enhance both the reactivity and selectivity (i.e., electron efficiency, ε ) of zero-valent iron (ZVI) in contaminant removal, which may make this technology cost-effective for a wider range of water treatment applications. However, current sulfidation methods involve either hazardous...

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Bibliographic Details
Published in:Environmental science & technology 2021-01, Vol.55 (1), p.645-654
Main Authors: Cai, Shichao, Chen, Bo, Qiu, Xiaojiang, Li, Jiamei, Tratnyek, Paul G, He, Feng
Format: Article
Language:English
Subjects:
Ambient temperature
Contaminants
Dechlorination
Electrons
Iron
Pollutant removal
Product safety
Rate constants
Selectivity
Sodium dithionite
Sodium sulfide
Sodium thiosulfate
Solvents
Sulfidation
Sulfur
Trichloroethene
Trichloroethylene
Water
Water Pollutants, Chemical
Water treatment
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Summary:Sulfidation can enhance both the reactivity and selectivity (i.e., electron efficiency, ε ) of zero-valent iron (ZVI) in contaminant removal, which may make this technology cost-effective for a wider range of water treatment applications. However, current sulfidation methods involve either hazardous or unstable sulfidation agents (e.g., Na S, Na S O , and Na S O ) or energy-intensive preparations (e.g., mechanochemical sulfidation with elemental sulfur). In this study, we demonstrate that very efficient sulfidation of microscale ZVI (mZVI) can be achieved at all S/Fe molar ratios (∼100% sulfidation efficiency, ε ) simply by direct reaction between elemental sulfur (S ) and ZVI in an aqueous suspension at ambient temperature. In comparison, the ε values obtained using Na S, Na S O , or Na S O as the sulfidation agents were only ∼23, ∼75, and ∼38%, respectively. The sulfidated mZVI produced using the new method reacts with trichloroethylene (TCE) with very high rates and electron efficiencies: rate constants and electron efficiencies were 800- and 79-fold higher than those of the unsulfidated mZVI. The enhanced performance of this material, together with the operational advantages of S for sulfidation (including safety, stability, and cost), may make it a desirable product for full-scale engineering applications.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.0c05397