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ORIGINAL RESEARCH ARTICLE

Comparative study on the CO2 capture performance of sludge pyrolysis biochar prepared with different inorganic dehydrating conditioners

Yingjie Huang1† ,  Yuexin Zhang1,2† ,  Rui Dong1 ,  Jianfeng Fang1 ,  Yizhou Li1 ,  Yang Yang1 ,  Tianfeng Tang3 ,  Jiangdi Deng1,4*
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1 Three Gorges Reservoir Area Environment and Ecology of Chongqing Observation and Research Station, Chongqing Three Gorges University, Wan Zhou, Chongqing, China
2 Emergency Environmental Bureau of the Industrial Park, Cuiping District, Yibin, Sichuan, China
3 Chongqing Liangping District Ecological Environment Bureau, Liangping, Chongqing, China
4 Chongqing GreenKarbon Environmental Protection Technology Co., Ltd., Chongqing, China
†These authors contributed equally to this work.
AJWEP, 026120081 https://doi.org/10.36922/AJWEP026120081
Received: 20 March 2026 | Revised: 23 April 2026 | Accepted: 6 May 2026 | Published online: 24 June 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

To address the limited understanding of how inorganic dehydrating conditioners affect the CO2 capture performance of sludge-derived biochar, this study investigated three representative conditioners: polyferric chloride, polyferric sulfate (PFS), and polyaluminosilicate ferric salt, and evaluated their influence on biochar properties and carbon dioxide (CO2) adsorption. The effects of conditioner dosage were first optimized, and two preparation routes, conventional ex situ pyrolysis and cyclic pyrolysis, were then compared. The resulting biochars were systematically characterized, and their adsorption behavior was analyzed using physicochemical characterization and adsorption kinetics modeling to elucidate the synergistic roles of conditioner type and pyrolysis mode. The results show that the biochar prepared from PFS-conditioned sludge by cyclic pyrolysis (SS-PFS cycle) exhibited the best performance at the optimal dosage ratio, achieving a CO2 adsorption capacity of 101.48 mg/g at 25 °C. Mechanistic analysis revealed that the SS-PFS cycle possessed a more developed pore structure, a richer surface functional group density, and a higher carbon defect density, all of which synergistically enhanced both physical and chemical adsorption of CO2. After 10 consecutive adsorption–desorption cycles, the material retained 58.94% of its initial adsorption capacity, indicating reasonable reusability. These findings confirm that combining PFS conditioning with cyclic pyrolysis is a viable strategy for improving the CO2 capture performance of sludge-derived biochar and provide both theoretical support and technical guidance for the high-value utilization of sewage sludge.

Keywords
Sludge
Biochar
CO2 capture
Pyrolysis
Inorganic dehydrating conditioners
Funding
This work was supported by the National Natural Science Foundation of China (grant number 51808089) and the Science and Technology Research Program of Chongqing Municipal Education Commission (Grant No. KJZD-M202501203).
Conflict of interest
The authors declare that they have no competing interests.
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Asian Journal of Water, Environment and Pollution, Electronic ISSN: 1875-8568 Print ISSN: 0972-9860, Published by AccScience Publishing
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