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

doi:10.1016/j.jhazmat.2020.123055

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

J Hazard Mater. 2020 Nov 15:399:123055. doi: 10.1016/j.jhazmat.2020.123055. Epub 2020 May 28.

Authors

Jiewen Luo¹, Litao Lin², Cun Liu³, Chao Jia¹, Tianyue Chen⁴, Yang Yang⁵, Minghao Shen¹, Hua Shang¹, Shaojie Zhou¹, Meiying Huang³, Yujun Wang³, Dongmei Zhou⁶, Jiajun Fan⁷, James H Clark⁸, Shicheng Zhang⁹, Xiangdong Zhu¹⁰

Affiliations

¹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China.
² Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; School of Energy and Power Engineering, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu 212003, China.
³ Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
⁴ School of Mathematical Science, Fudan University, Shanghai 200438, China.
⁵ Bioenergy Research Group, European Bioenergy Research Institute, Aston University, Birmingham B4 7ET, UK.
⁶ School of the Environment, Nanjing University, Xianlin Ave. 163, Nanjing 210023, China.
⁷ Green Chemistry Centre of Excellence, Department of Chemistry, University of York, York, YO10 5DD, UK.
⁸ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; Green Chemistry Centre of Excellence, Department of Chemistry, University of York, York, YO10 5DD, UK.
⁹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China.
¹⁰ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China. Electronic address: zxdjewett@fudan.edu.cn.

PMID: 32526445
DOI: 10.1016/j.jhazmat.2020.123055

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.

Keywords: Biochar; Metal cyanide; Theoretical calculation; Toxic substance.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biomass
Charcoal*
Chlorides
Metals*

Substances

Chlorides
Metals
biochar
Charcoal