In-depth comparison of morphology, microstructure, and pathway of char derived from sewage sludge and relevant model compounds

Research output: Contribution to journalArticle


  • Chuan Peng
  • Yunbo Zhai
  • Bei Wang
  • Shanhong Li
  • Tengfei Wang
  • Caiting Li
  • Yun Zhu

Colleges, School and Institutes

External organisations

  • College of Environmental Science and Engineering, Hunan University, Changsha 410082, P. R. China
  • College of Electrical and Information Engineering, Hunan University, Changsha 410082, P. R. China


Hydrothermal conversion (HTC) of sewage sludge (SS) and its relevant model compounds such as cellulose, glucose, lignin and soybean protein (substitute for protein) was experimentally conducted at moderate reaction temperature of 260 °C for 60 min. The structural properties, carbon-containing groups, and microstructure of the char were characterised by several techniques. The results revealed that more benzene rings were formed by small clusters and the C-O bond on Aryl-alkyl ether decomposed on the surface particles during the HTC process. In addition, the catalyst Zeolite Socony Mobil–5 (ZSM-5, Si/Al: 300) showed an excellent performance on the high graphite degree of the char under moderate reaction temperature of 260 °C. In particular, cellulose has the most dramatic influence on the depolymerisation of C-(C,H). As evidenced with SEM, the size of the char derived from SS with ZSM-5 catalyst is 10-15μm, which is smaller than the char without catalyst. A mechanism for derivation of char from individual model compounds is proposed. The end products of lignin are composed of polyaromatic char, while the composition of the char derived from protein suggests that polymerisation may occur during hydrothermal reaction leading to formation of structures with N-containing compounds.


Original languageEnglish
Pages (from-to)432-440
Number of pages9
JournalWaste Management: international journal of integrated waste management, science and technology
Early online date14 Nov 2019
Publication statusPublished - 1 Feb 2020


  • sewage sludge, model compounds, char morphology, char microstructure, hydrothermal conversion, reaction pathway