Co-production of biochar and carbon nanotube from sewage sludge in a two-stage process coupling pyrolysis and catalytic chemical vapor deposition

• Published in: Waste Disposal and Sustainable Energy
• Main Author: Mohd Ghazali M.S.; Md Zaini M.S.; Arshad M.; Syed-Hassan S.S.A.
• Format: Article
• Language: English
• Published: Springer 2024
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85188658583&doi=10.1007%2fs42768-024-00194-2&partnerID=40&md5=b952e1f50f0da9f291bd48ba1a36cdae

This study explores the potential of valorizing sewage sludge as a carbon source for the co-production of biochar and carbon nanomaterial via a two-stage thermal-catalytic process. In the first stage, sewage sludge underwent slow pyrolysis, resulting in a biochar yield of 66% (in weight) at 550 °C. The resulting pyrolysis vapor was then introduced into a second reactor, where catalytic chemical vapor deposition (CCVD) took place in the presence of a cobalt catalyst, leading to the production of carbon nanotubes (CNTs). It was found that CNTs with an inner diameter of ~ 3.2 nm and an outer diameter of 20–40 nm can be formed in the second stage reactor at temperatures between 650 °C and 950 °C with a maximum yield of 30% (in weight) under the employed experimental conditions. The obtained CNTs displayed a multiwall structure, exhibited a lack of crystallinity, and demonstrated a high level of disorder. The research findings also indicate that temperature exerts a significant influence on both the yield and properties of the CNTs synthesized. Graphical abstract: (Figure presented.) © Zhejiang University Press 2024.