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| Sulfidation enhanced Cr(Ⅵ) reduction by zerovalent iron under different environmental conditions: A mechanistic study |
| Received:October 25, 2020 |
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| KeyWord:sulfidated zerovalent iron;Cr(Ⅵ);electrochemical;electron transfer |
| Author Name | Affiliation | E-mail | | LIU Li | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China | | | LIANG Le-bin | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China | | | SHI Yue | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China | | | WANG Xiao-zhi | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China | | | FENG Ke | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China | | | WANG Sheng-sen | School of Environmental Science and Engineering, Yangzhou University, Yangzhou 225127, China | wangss@yzu.edu.cn |
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| Abstract: |
| Pristine zerovalent iron(ZVI) was sulfidated with sodium thiosulfate to improve its hexavalent chromium[Cr2O72-, Cr(Ⅵ)] removal capacity. The resulting sulfidated ZVI(S-ZVI) was tested for Cr(Ⅵ) sorption under different environmental conditions and then characterized using spectral techniques. The results showed that S-ZVI composites comprised the ZVI core surrounded by a FeSx shell, and the surface area was almost doubled relative to pristine ZVI. Sulfidation improved Cr(Ⅵ) sorption and reduction compared with ZVI, demonstrated in batch sorption experiments. The sorption data at a pH of 3 were better fitted with the second-order kinetics model and Langmuir isotherm model, revealing that Cr(Ⅵ) removal by S-ZVI was approximately three times that of ZVI. Desorption and XPS of exhausted sorbents clearly showed that Cr(Ⅵ) was dominantly reduced to Cr(Ⅲ), which was further adsorbed and precipitated on the sorbent surfaces. Sulfidation significantly increased the electrical conductivity of ZVI, thus improving its electron transfer rate during Cr(Ⅵ) reduction. Lower pH and elevated temperature were more favorable for Cr(Ⅵ) removal by both sorbents, whereas humic acid inhibited Cr(Ⅵ) removal. To conclude, Cr(Ⅵ) removal by S-ZVI invoke reduction, adsorption, and coprecipitation mechanisms, and the better performance of S-ZVI is likely ascribed to favorable electrochemical properties and a larger surface area. |
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