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

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

Research output: Contribution to journalArticlepeer-review


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.
Original languageEnglish
Article number123055
JournalJournal of Hazardous Materials
Early online date28 May 2020
Publication statusPublished - 15 Nov 2020

Bibliographical note

Funding Information:
This work was supported by the Shanghai Natural Science Foundation of China (NO. 19ZR1403800 ) and National Natural Science Foundation of China (No. 21876030 ).


  • Biochar
  • Metal cyanide
  • Theoretical calculation
  • Toxic substance


Dive into the research topics of 'Reveal a hidden highly toxic substance in biochar to support its effective elimination strategy'. Together they form a unique fingerprint.

Cite this