@article{Cao2026, 
author = {Jun Cao and Hao Zhang and Ji-peng Sun and Xin Wang and Tao Liang and Yi-chao Wang and Hua-lun Zhu},
title = {Pyrolysis temperature-dependent variations in spectral and molecular characteristics of water- and alkali-extractable organic matter derived from biochar produced by municipal sludge},
year = {2026},
journal = {Water Science and Engineering},
volume = {19},
number = {2},
pages = {211-222},
keywords = {Dissolved organic matter, Sludge-based biochar, Residence time, EEM-PARAFAC, FT-ICR MS},
url = {https://www.sciopen.com/article/10.1016/j.wse.2026.02.004},
doi = {10.1016/j.wse.2026.02.004},
abstract = {Biochar-derived dissolved organic matter (BDOM) plays a crucial role in environmental processes. This study investigated the characteristics of water-extractable organic matter (WEOM) and alkali-extractable organic matter (AEOM) from sludge-derived biochar produced across different pyrolysis temperatures, combining spectroscopic analysis with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Dissolved organic carbon (DOC) concentrations in WEOM and AEOM declined significantly (from 5.72 mg/g to 1.95 mg/g and from 5.93 mg/g to 2.36 mg/g, respectively) with increases in temperature from 400℃ to 500℃ before increasing again at 600℃. AEOM generally exhibited higher DOC concentrations than WEOM. Three fluorescent components were identified: a humic-like component C1 with two peaks (one at an excitation wavelength (λEx) of 230 nm and an emission wavelength (λEm) of 400 nm and the other at λEx = 310 nm and λEm = 400 nm), an ultraviolet C (UVC) humic-like component C2 with a single peak (λEx = 260 nm and λEm = 460 nm), and a protein-like component C3 with two peaks (one at λEx = 220 nm and λEm = 290 nm and the other at λEx = 285 nm and λEm = 290 nm). AEOM was predominantly composed of polycyclic aromatic compounds, aromatic formulas, lignin, and nitrogen-containing aliphatic compounds, which altogether accounted for more than 75% of its composition. With increasing pyrolysis temperature, the relative abundance of most aromatic structures decreased, while N-aliphatic compounds became more prominent. The humification degree and molecular weight of BDOM increased with temperature rises to 500℃−550℃ and then declined, with protein-like C3 peaking within this temperature range. FT-ICR MS revealed a significant reduction in lignin content at 550℃. These results indicate that 500℃−550℃ represents a key inflection point in dissolved organic matter (DOM) transformation and an optimal pyrolysis range for producing environmentally favorable biochar.}
}