Biochar conductivity and electron donating capability control Cr(VI) bioreduction

Peng Zhang; Bingqian Zhu; Shunling Li; Wei Du; Hongbo Peng; Bo Liu; Zhao Wang

doi:10.1016/j.chemosphere.2023.138950

Biochar conductivity and electron donating capability control Cr(VI) bioreduction

Chemosphere. 2023 Aug:333:138950. doi: 10.1016/j.chemosphere.2023.138950. Epub 2023 May 15.

Authors

Peng Zhang¹, Bingqian Zhu², Shunling Li², Wei Du², Hongbo Peng³, Bo Liu², Zhao Wang²

Affiliations

¹ Yunnan Provincial Key Laboratory of Soil Carbon Sequestration and Pollution Control, Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China. Electronic address: da.feipeng@163.com.
² Yunnan Provincial Key Laboratory of Soil Carbon Sequestration and Pollution Control, Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, China.
³ Faculty of Modern Agricultural Engineering, Kunming University of Science & Technology, Kunming, 650500, China.

PMID: 37196795
DOI: 10.1016/j.chemosphere.2023.138950

Abstract

Biochar can facilitate Cr(VI) bioreduction, but it is still undetermined which biochar property control this process. We observed that the apparent Cr(VI) bioreduction by Shewanella oneidensis MR-1 could be identified as a fast and a relatively slow processes. The fast-bioreduction rates (r_f0) were 2-15 times higher than the slow-bioreduction rates (r_s0). In this study, we investigated the kinetics and efficiency of biochar in promoting Cr(VI) reduction by S. oneidensis MR-1 in the neutral solution using a "dual-process model" (fast and slow processes), and analyzed the mechanisms of biochar concentration, conductivity, particle size and other properties on these two processes. The correlation analysis of these rate constants and biochar properties was carried out. The fast-bioreduction rates were associated with higher conductivity and smaller particle sizes of biochar, which facilitated the direct electron transfer from Shewanella oneidensis MR-1 to Cr(VI). The Cr(VI) slow-bioreduction rates (r_s0) were mainly determined by the electron donating capability of biochar and independent of the cell concentration. Our results suggested that Cr(VI) bioreduction was mediated by both electron conductivity and redox potential of biochar. This result is instructive for biochar production. Manipulating biochar properties to control fast and slow Cr(VI) reduction may be helpful to effectively remove or detoxify Cr(VI) in the environment.

Keywords: Chromium; Extracellular electron transfer; Shewanella.

MeSH terms

Chromium
Electrons*
Oxidation-Reduction
Shewanella*

Substances

chromium hexavalent ion
biochar
Chromium

Supplementary concepts

Shewanella oneidensis