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Reveal a hidden highly toxic substance in biochar to support its effective elimination strategy

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Author(s)

  • Jiewen Luo
  • Litao Lin
  • Cun Liu
  • Chao Jia
  • Tianyue Chen
  • Yang Yang
  • Minghao Shen
  • Hua Shang
  • Shaojie Zhou
  • Meiying Huang
  • Yujun Wang
  • Dongmei Zhou
  • Jiajun Fan
  • James H. Clark
  • Shicheng Zhang
  • Xiangdong Zhu

Department/unit(s)

Publication details

JournalJournal of hazardous materials
DateAccepted/In press - 26 May 2020
DateE-pub ahead of print - 28 May 2020
DatePublished (current) - 15 Nov 2020
Volume399
Number of pages8
Early online date28/05/20
Original languageEnglish

Abstract

With the aim to develop optimized biochar with minimal contaminants, it is important significance to broaden the understanding of biochar. Here, we disclose for the first time, a highly toxic substance (metal cyanide, MCN, such as KCN or NaCN) in biochar. The cyanide ion (CN) content in biochar can be up to 85,870 mg/kg, which is determined by the inherent metal content and type in the biomass with K and Na increasing and Ca, Mg and Fe decreasing its formation. Density functional theory (DFT) analysis shows that unstable alkali oxygen-containing metal salts such as K2CO3 can induce an N rearrangement reaction to produce for example, KOCN. The strong reducing character of the carbon matrix further converts KOCN to KCN, thus resulting biochar with high risk. However, the stable Mg, Ca and Fe salts in biomass cannot induce an N rearrangement reaction due to their high binding energies. We therefore propose that high valent metal chloride salts such as FeCl3 and MgCl2 could be used to inhibit the production of cyanide via metal interactive reaction. These findings open a new point of view on the potential risk of biochar and provide a mitigation solution for biochar's sustainable application.

Bibliographical note

© 2020 Published by Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy.

    Research areas

  • Biochar, Metal cyanide, Theoretical calculation, Toxic substance

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