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Enhanced Transformation of Cr(VI) by Heterocyclic-N within Nitrogen-Doped Biochar: Impact of Surface Modulatory Persistent Free Radicals (PFRs)

  • Shishu Zhu
    Shishu Zhu
    School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China
    Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-Sen University, Guangzhou 510275, PR China
    More by Shishu Zhu
  • Xiaochen Huang
    Xiaochen Huang
    School of Environment, Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou, 510632, China
  • Xiaobao Yang
    Xiaobao Yang
    Department of Physics, South China University of Technology, Guangzhou 510640, P. R. China
    More by Xiaobao Yang
  • Peng Peng
    Peng Peng
    Department of Mechanics and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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  • Zhipeng Li
    Zhipeng Li
    School of Marine Science and Technology, Harbin Institute of Technology at Weihai, Weihai 264209, China
    More by Zhipeng Li
  • , and 
  • Chao Jin*
    Chao Jin
    School of Environmental Science and Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China
    Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-Sen University, Guangzhou 510275, PR China
    *Email: [email protected]
    More by Chao Jin
Cite this: Environ. Sci. Technol. 2020, 54, 13, 8123–8132
Publication Date (Web):June 3, 2020
Copyright © 2020 American Chemical Society
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Redox processes mediated by biochar(BC) enhanced the transformation of Cr(VI), which is largely dependent on the presence of PFRs as electron donors. Natural or artificial dopants in BC’s could regulate inherent carbon configuration and PFRs. Until recently, the modulation of PFRs and transformation of Cr(VI) in BC by nonmetal-heterocyclic dopants was barely studied. In this study, changes in PFRs introduced by various nitrogen-dopants within BC are presented and the capacity for Cr(VI) transformation without light was investigated. It was found N-dopants were effectively embedded in carbon lattices through activated-Maillard reaction thus altering their charge and PFRs. Transformation of Cr(VI) in N doped biochar relied on mediated direct reduction by surface modulatory PFRs. The kinetic rate of transformation of Cr(VI) was increased 1.4–5 fold in N-BCs compared to nondoped BCs. Theortical calculation suggested a deficiency in surface electrons induced Lewis acid–base bonding which could acted as a bridge for electron transfer. Results of PCA and orbital energy indicated a colinear relationship between PFRs and pyrrolic N, as well as its dual-mode transformation of Cr(VI). This study provides an improved understanding of how N-doped BC contributes to the evolution of PFRs and their corresponding impacts on the transformation of Cr(VI) in environments.

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  • Five texts, 3 tables, and 14 Figures; Details of the preparation methods for N-doping BCs, kinetics experiments and isotherm models, DFT calculation, and EPR experiments; Information relating to the characterization of different BCs and comparison of Cr(VI) decay by different organic carbons is also presented, as well as background on sorption isotherms and Cr(VI) transformation. Quenching results of Cr(VI) decay as well as the results of linear regression are also provided (PDF)

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