Electron donation of Fe-Mn biochar for chromium(VI) immobilization: Key roles of embedded zero-valent iron clusters within iron-manganese oxide

The dense surface passivation layer on zero-valent iron (ZVI) restricts its efficiency for water decontamination, causing a poor economy and waste of resources. Herein, we found that the ZVI on Fe-Mn biochar could afford a high electron-donating efficiency for the Cr(VI) reduction and immobilization...

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Veröffentlicht in:Journal of hazardous materials 2023-08, Vol.456, p.131632-131632, Article 131632
Hauptverfasser: Xu, Zibo, Sun, Mingzhe, Xu, Xiaoyun, Cao, Xinde, Ippolito, James A., Mohanty, Sanjay K., Ni, Bing-Jie, Xu, Shuguang, Tsang, Daniel C.W.
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Sprache:eng
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Zusammenfassung:The dense surface passivation layer on zero-valent iron (ZVI) restricts its efficiency for water decontamination, causing a poor economy and waste of resources. Herein, we found that the ZVI on Fe-Mn biochar could afford a high electron-donating efficiency for the Cr(VI) reduction and immobilization. Over 78.0% of Fe in the Fe-Mn biochar was used for the Cr(VI) reduction and immobilization, i.e., 56.2 − 161.7 times higher than the commercial ZVI (0.5%) and modified ZVI (0.9 −1.3%), indicating that the unique ZVI species in Fe-Mn biochar offered an outstanding Fe utilization efficiency. We proposed that oxygen atoms in the FeO in the FeMnO2 precursor were removed during pyrolysis with biochar while the MnO skeleton was preserved, forming the embedded ZVI clusters within Fe-Mn oxide. The unique structure inhibited the formation of the Fe-Cr complex on Fe(0), which would facilitate the electron transfer between core Fe(0) and Cr(VI). Moreover, the surface FeMnO2 inhibited the diffusion of Fe and facilitated its affinity with pollutants, thus supporting higher efficiency for pollutant immobilization. The preserved performance of Fe-Mn biochar was proved in industrial wastewater and after long-term oxidation process, and the economic benefit was evaluated. This work provides a new approach for developing active ZVI-based materials with high Fe utilization efficiency and economics for water pollution control. [Display omitted] •Over 78.0% of Fe in the Fe-Mn biochar can be used for Cr(VI) immobilization in wastewater.•Fe utilization efficiency of Fe-Mn biochar is up to 161.6 times higher than zero-valent iron (ZVI).•Fe-Mn biochar sustains its high efficiency even after interactions with impurities or oxidants.•Embedded ZVI clusters are formed by the reduction of FeMnO2 during pyrolysis with biochar.•The unique iron species, embedded ZVI clusters, are vital to outstanding utilization efficiency.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2023.131632