Influence of pyrolysis temperature on properties and environmental safety of heavy metals in biochars derived from municipal sewage sludge

Junwei JIN, Yanan LI, Jianyun ZHANG, Sheng Chun WU, Yucheng CAO, Peng LIANG, Jin ZHANG, Ming Hung WONG, Minyan WANG, Shengdao SHAN, Peter CHRISTIE

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191 Citations (Scopus)

Abstract

Dried raw sludge was pyrolyzed at temperatures ranging from 400 to 600 °C at the increase of 50 °C intervals to investigate the influence of pyrolysis temperature on properties and environmental safety of heavy metals in biochar derived from municipal sewage sludge. The sludge biochar yield decreased significantly with increasing pyrolysis temperature but the pH, ash content and specific surface area increased. Conversion of sludge to biochar markedly decreased the H/C and N/C ratios. FT-IR analysis confirmed a dramatic depletion of H and N and a higher degree of aromatic condensation in process of biochar formation at higher temperatures. The total concentrations of Cu, Zn, Pb, Cr, Mn, and Ni increased with conversion of sludge to biochar and increasing pyrolysis temperature. However, using BCR sequential extraction and analysis, it was found that most of the heavy metals existed in the oxizable and residual forms after pyrolysis, especially at 600 °C, resulting in a significant reduction in their bioavailability, leading to a very low environmental risk of the biochar. The present study indicates pyrolysis is a promising sludge treatment method for heavy metals immobilization in biochar, and highlights the potential to minimize the harmful effects of biochar by controlling pyrolysis temperature. Copyright © 2016 Elsevier B.V.
Original languageEnglish
Pages (from-to)417-426
JournalJournal of Hazardous Materials
Volume320
Early online dateAug 2016
DOIs
Publication statusPublished - Dec 2016

Citation

Jin, J., Li, Y., Zhang, J., Wu, S., Cao, Y., Liang, P., et al. (2016). Influence of pyrolysis temperature on properties and environmental safety of heavy metals in biochars derived from municipal sewage sludge. Journal of Hazardous Materials, 320, 417-426.

Keywords

  • Sewage sludge biochar
  • Heavy metals
  • Thermal pyrolysis
  • BCR sequential extraction
  • Environmental risk assessment

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