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Key role of hydrogen atoms in the preparation of sulfidated zero valent iron.

Authors :: Fan B
Chen S
Zhu C
Zhu F
Huang D
Si D
Zhou B
Zhou D
He F
Gao S
Source :: Water research [Water Res] 2024 Jun 01; Vol. 256, pp. 121573. Date of Electronic Publication: 2024 Apr 05.
Publication Year :: 2024
Abstract: Sulfidated zero valent iron (ZVI) is a popular material for the reductive degradation of halogenated organic pollutants. Simple and economic synthesis of this material is highly demanded. In this study, sulfidated micro/nanostructured ZVI (MNZVI) particles were prepared by simply heating MNZVI particles and sulfur elements (S <superscript>0</superscript> ) in pure water (50℃). The iron oxides on the surface of MNZVI particles were conducive to sulfidation reaction, indicating the formation of iron-sulphide minerals (FeS <subscript>x</subscript> ) on the surface of MNZVI particles might not be from the direct reaction of Fe <superscript>0</superscript> with S <superscript>0</superscript> (Fe <superscript>0</superscript> and S <superscript>0</superscript> acted as reductant and oxidant, respectively). As an important reductant, hydrogen atom (H•) can be generated from the reduction of H <superscript>+</superscript> by MNZVI particles and participate in the formation of FeS <subscript>x</subscript> . Quenching experiment and cyclic voltammetry analysis proved the existence of H• on the surface of MNZVI particles. DFT calculation found that the potential barrier of H•/S <superscript>0</superscript> and Fe <superscript>0</superscript> /S <superscript>0</superscript> were 1.91 and 7.24 eV, respectively, indicating that S <superscript>0</superscript> would preferentially react with H• instead of Fe <superscript>0</superscript> . The formed H• can quickly react with S <superscript>0</superscript> to generate hydrogen sulfide (H <subscript>2</subscript> S), which can further react with iron oxides such as α-Fe <subscript>2</subscript> O <subscript>3</subscript> on the surface of MNZVI particles to form FeS <subscript>x</subscript> . In addition, the H <subscript>2</subscript> partial pressure in water significantly affected the amount of H• generated, thereby affecting the sulfidation efficiency. For TCE degradation, as the sulfur loading of sulfidated MNZVI particles increased, the contribution of H• significantly decreased while the contribution of direct electron transfer increased. This study provided new insights into the synthesis mechanism of sulfidated ZVI in water.<br />Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.<br /> (Copyright © 2024 Elsevier Ltd. All rights reserved.)