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Updated: Aug 27, 2025

Physical, Chemical and Biological Characterization of Six Biochars Produced for the Remediation of Contaminated Sites
Published on: November 28, 2014
Enhanced Cr(VI) bioreduction by biochar: Insight into the persistent free radicals mediated extracellular electron
Cheng Yu1, Xiaoxi Zhu1, Abdelkader Mohamed2
1College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, PR China.
Abstract:
Biochar can act as a shuttle to accelerate the extracellular electron transfer (EET) by exoelectrogens. However, it is poorly understood how the persistent free radicals (PFRs) in biochar affected EET and the redox reaction. Herein, the effects of the biochar and chitosan modified biochar (CBC) on the Cr(VI) bioreduction by Shewanella oneidensis MR-1 (MR-1) was investigated. Kinetic study indicated that the Cr(VI) bioreduction rate constant by MR-1 was increased by 1.8-33.7 folds in the presence of biochar, and by 2.7-60.2 folds in the presence of CBC, respectively. Moreover, Cr(VI) bioreduction rates increased with the decreasing pH. Results suggested that the electrostatic attraction between Cr(VI) and redox-active particles could accelerate the EET by c-cytochrome due to the promotion of the Cr(VI) migration from aqueous phase to biochar or CBC. Electron paramagnetic resonance analysis suggested that the PFRs affected the electron transfer from the ·O2- generated by MR-1 to Cr(VI) and accelerate the Cr(VI) bioreduction. Remarkably, in the presence of PFRs, this electron shuttling process was dependent on the non-metal-reducing respiratory pathway. Our results offer new insights that free radicals may be widely involved in the EET and strongly impact on the redox reaction in the environment.
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