Electroactive Fe-biochar for redox-related remediation of arsenic and chromium: Distinct redox nature with varying iron/carbon speciation

Zibo Xu, Zhonghao Wan, Yuqing Sun, Bin Gao, Deyi Hou, Xinde Cao, Michael Komárek, Yong Sik Ok, Daniel C.W. Tsang

Research output: Contribution to journalArticlepeer-review

64 Citations (Scopus)

Abstract

Electroactive Fe-biochar has attracted significant attention for As(III)/Cr(VI) immobilization through redox reactions, and its performance essentially lies in the regulation of various Fe/C moieties for desired redox performance. Here, a series of Fe-biochar with distinct Fe/C speciation were rationally produced via two-step pyrolysis of iron minerals and biomass waste at 400−850 °C (BCX-Fe-Y, X and Y represented the first- and second-step pyrolysis temperature, respectively). The redox transformation of Cr(VI) and As(III) by Fe-biochar was evaluated in simulated wastewater under oxic or anoxic conditions. Results showed that more effective Cr(VI) reduction could be achieved by BCX-Fe-400, while a higher amount of As (III) was oxidized by BCX-Fe-850 under the anoxic environment. Besides, BCX-Fe-400 could generate more reactive oxygen species (e.g., OH) by reducing the O2, which enhanced the redox-related transformation of pollutants under the oxic situation. The evolving redox performance of Fe-biochar was governed by the transition of the redox state from reductive to oxidative related to the Fe/C speciation. The small-sized amorphous/low-crystalline ferrous minerals contributed to a higher electron-donating capacity (0.43−1.28 mmol g−1) of BCX-Fe-400. In contrast, the oxidative surface oxygen-functionalities (i.e., carboxyl and quinoid) on BCX-Fe-850 endowed a stronger electron-accepting capacity (0.71−1.39 mmol g−1). Moreover, the graphitic crystallites with edge-type defects and porous structure facilitated the electron transfer, leading to a higher electron efficiency of BCX-Fe-850. Overall, we unveiled the roles of both Fe and C speciation in maneuvering the redox reactivity of Fe-biochar, which can advance our rational design of electroactive Fe-biochar for redox-related environmental remediation.

Original languageEnglish
Article number128479
JournalJournal of hazardous materials
Volume430
DOIs
Publication statusPublished - 2022 May 15

Bibliographical note

Funding Information:
We appreciate the financial support from the Hong Kong Environment and Conservation Fund (Project 101/2020) and Hong Kong Research Grants Council (PolyU 15222020) for this study. We acknowledge the equipment support provided by the University Research Facility in Chemical and Environmental Analysis (UCEA) of the Hong Kong Polytechnic University and the Instrumental Analysis Center of Shanghai Jiao Tong University. Michael Komárek is supported by the Czech Science Foundation (21–23794J).

Funding Information:
We appreciate the financial support from the Hong Kong Environment and Conservation Fund (Project 1 01/202 0 ) and Hong Kong Research Grants Council ( P olyU 1522202 0 ) for this study. We acknowledge the equipment support provided by the University Research Facility in Chemical and Environmental Analysis (UCEA) of the Hong Kong Polytechnic University and the Instrumental Analysis Center of Shanghai Jiao Tong University. Michael Komárek is supported by the Czech Science Foundation ( 2 1–23794 J ).

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • Electron transfer
  • Engineered biochar
  • Mineral transformation
  • Reduction-oxidation
  • Sustainable waste management

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis

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