Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

Jiang Xu; Astrid Avellan; Hao Li; Xitong Liu; Vincent Noël; Zimo Lou; Yan Wang; Rälf Kaegi; Graeme Henkelman; Gregory V Lowry

doi:10.1002/adma.201906910

Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

Adv Mater. 2020 Apr;32(17):e1906910. doi: 10.1002/adma.201906910. Epub 2020 Mar 12.

Authors

Jiang Xu^{1

2}, Astrid Avellan^{1

2}, Hao Li³, Xitong Liu¹, Vincent Noël⁴, Zimo Lou¹, Yan Wang⁵, Rälf Kaegi⁶, Graeme Henkelman³, Gregory V Lowry^{1

2}

Affiliations

¹ Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
² Center for Environmental Implications of NanoTechnology, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
³ Department of Chemistry and the Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, Texas, 78712, USA.
⁴ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, 94025, USA.
⁵ Department of Civil and Environmental Engineering, University of Pittsburgh, Pittsburgh, PA, 15261, USA.
⁶ Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600, Dübendorf, Switzerland.

PMID: 32162726
DOI: 10.1002/adma.201906910

Abstract

Sulfidized nanoscale zerovalent iron (SNZVI) is a promising material for groundwater remediation. However, the relationships between sulfur content and speciation and the properties of SNZVI materials are unknown, preventing rational design. Here, the effects of sulfur on the crystalline structure, hydrophobicity, sulfur speciation, corrosion potential, and electron transfer resistance are determined. Sulfur incorporation extended the nano-Fe⁰ BCC lattice parameter, reduced the Fe local vacancies, and lowered the resistance to electron transfer. Impacts of the main sulfur species (FeS and FeS₂ ) on hydrophobicity (water contact angles) are consistent with density functional theory calculations for these FeS_x phases. These properties well explain the reactivity and selectivity of SNZVI during the reductive dechlorination of trichloroethylene (TCE), a hydrophobic groundwater contaminant. Controlling the amount and speciation of sulfur in the SNZVI made it highly reactive (up to 0.41 L m^-2 d^-1 ) and selective for TCE degradation over water (up to 240 moles TCE per mole H₂ O), with an electron efficiency of up to 70%, and these values are 54-fold, 98-fold, and 160-fold higher than for NZVI, respectively. These findings can guide the rational design of robust SNZVI with properties tailored for specific application scenarios.

Keywords: environmental nanotechnology; groundwater remediation; rational design; sulfidized nanoscale zerovalent iron; sulfur speciation.

Abstract

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