Sulfidation and, more recently, nitriding have been recognized as promising modifications to enhance the selectivity of nanoscale zero-valent iron (nZVI) particles for trichloroethene (TCE). Herein, we investigated the performance of iron nitride (FexN) nanoparticles in the removal of a broader range of chlorinated ethenes (CEs), including tetrachloroethene (PCE), cis-1,2-dichloroethene (cis-DCE), and their mixture with TCE, and compared it to the performance of sulfidated nZVI (S-nZVI) prepared from the same precursor nZVI. Two distinct types of iron nitride (FexN) nanoparticles, containing γ'-Fe4N and ε-Fe2-3N phases, exhibited substantially higher PCE and cis-DCE dechlorination rates compared to S-nZVI. A similar effect was observed with a CE mixture, which was completely dechlorinated by both types of FexN nanoparticles within 10 days, whereas S-nZVI was able to remove only about half of the amount, most of which being TCE. Density functional theory calculations further revealed that the cleavage of the first C-Cl bond was the rate-limiting step for all CEs dechlorinated on the γ'-Fe4N(001) surface, with the reaction barriers of PCE and cis-DCE being 29.9, and 40.8 kJ mol-1, respectively. FexN nanoparticles proved to be highly effective in the remediation of PCE, cis-DCE, and mixed CE contamination.

Department of Environmental Geosciences Centre for Microbiology and Environmental Systems Science University of Vienna Josef Holaubek Platz 2 UZA 2 1090 Vienna Austria

Regional Centre of Advanced Technologies and Materials Czech Advanced Technology and Research Institute Palacký University Šlechtitelů 27 779 00 Olomouc Czech Republic

University of Natural Resources and Life Sciences Vienna Department of Forest and Soil Sciences Institute of Soil Research Peter Jordan Straße 82 1190 Vienna Austria

University of Natural Resources and Life Sciences Vienna Department of Forest and Soil Sciences Institute of Soil Research Peter Jordan Straße 82 1190 Vienna Austria; Department of Environmental Geosciences Palacký University Šlechtitelů 27 779 00 Olomouc Czech Republic

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