Synthesis of sewage sludge biochar in molten salt environment for advanced wastewater treatment: Performance enhancement, carbon footprint and environmental impact reduction

Sewage sludge (SS) pyrolysis to produce biochar is a vital approach for treating and utilizing SS, while reducing the carbon footprint of SS disposal. However, the high inorganic content in SS results in low carbon content and underdeveloped pore structure of biochar prepared under inert atmospheres...

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Bibliographic Details
Published in:Water research (Oxford) 2024-02, Vol.250, p.121072-121072, Article 121072
Main Authors: Fan, Zeyu, Zhou, Xian, Lu, Qi, Gao, Zhuo Fan, Deng, Shanshan, Peng, Ziling, Han, Wei, Chen, Xia
Format: Article
Language:English
Subjects:
Carbon
Carbon Footprint
Carbonates
Charcoal - chemistry
Environmental Pollutants
Sewage - chemistry
Sodium Chloride
Wastewater
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Summary:Sewage sludge (SS) pyrolysis to produce biochar is a vital approach for treating and utilizing SS, while reducing the carbon footprint of SS disposal. However, the high inorganic content in SS results in low carbon content and underdeveloped pore structure of biochar prepared under inert atmospheres. There is a significant risk of secondary pollutant emissions, including CO , SO , and NO . In this study, we propose an innovative approach that utilizes excess molten salts, specifically a Li-Na-K molten carbonate (MC) and a Li-Na-K molten chloride (MCH), to create a medium-temperature liquid phase reaction environment (500 °C) for SS pyrolysis. This environment promotes the functional enhancement of biochar (SSB-MC and SSB-MCH) and in-situ absorption of secondary pollutants. The pore structure of SSB-MC and SSB-MCH are greatly optimized. Thanks to the dissolution of calcium-silicon-aluminum-based minerals by molten salt, the carbon content is also significantly increased. The increased specific surface area and surface-enriched functional groups (O, N, P, etc.) of SSB-MC result in greatly enhanced adsorption performance for Rhodamine B (27.9 to 89.1 mg g ). SSB-MCH, due to the increased iron and phosphorus doping, also exhibits enhanced Fenton oxidation capability. Life cycle assessments demonstrate that the molten salt processes effectively reduce the carbon footprint, energy consumption, and environmental impact.
ISSN:0043-1354
1879-2448
DOI:10.1016/j.watres.2023.121072