Abstract
The reductive removal of redox-reactive contaminants, including 2,4-dinitrotoluene, 4-chlorophenol, chromate, and selenate, using biochar-coated metals and the relationship between reduction kinetics and electrochemical properties of biochar-coated metals were examined. To investigate the role of electrochemical properties, one-electron-transfer electrochemical reduction and oxidation mediators were used to determine electron-accepting capacities (EACs) and electron-donating capacities (EDCs) of biochar, zero-valent iron [Fe(0)], FeS, zero-valent zinc [Zn(0)], biochar-coated Fe(0), biochar-coated FeS, and biochar-coated Zn(0). Kinetic analysis showed that biochar coating resulted in decreasing the reductive transformation of contaminants by biochar-coated metals, suggesting that the sorbed molecules were further reduced to reduction products. Biochar, metals, and biochar-coated metal EDCs were an order of magnitude higher than their EACs, ranging between 11.01 and 38.61 mmol e−/g. The linear relationship between the EDCs and kinetic rates revealed that electron transfer from the core metal to sorbed contaminant oxidation is responsible for the reductive removal. A significant and irreversible EDC decrease generates electrons for the reductive transformation. To our knowledge, it is the first attempt to examine the electrochemical properties of metal-biochar composites and their relationship with reduction kinetics of various contaminants. Our results indicate that biochar-coated metals can be used as a sorbent and reductant for redox-reactive contaminants in subsurface environments.
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Acknowledgments
This work was supported by a National Research Foundation (NRF) of Korea grant funded by the Korean government (MSIT) (2020R1A2C1010855). This work was also supported in part by a Korea Institute for Advanced of Technology (KIAT) grant funded by the Korea Government (MOTIE) (P0008421).
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Seo, Y.D., Oh, S.Y., Rajagopal, R. et al. Redox-reactive contaminant removal using biochar-coated metals: the role of electrochemical properties. Int. J. Environ. Sci. Technol. 19, 4209–4220 (2022). https://doi.org/10.1007/s13762-021-03452-6
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DOI: https://doi.org/10.1007/s13762-021-03452-6