Research on preparation of red-mud-modified sludge-based biochar and its phosphorus adsorption efficiency and mechanism

ZHANG Chao; XIONG Renjiu; CAI Meiqiang; DONG Chunying

doi:10.13205/j.hjgc.202607018

Volume 44 Issue 7

Jul. 2026

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Article Navigation > ENVIRONMENTAL ENGINEERING > 2026 > 44(7): 179-190

ZHANG Chao, XIONG Renjiu, CAI Meiqiang, DONG Chunying. Research on preparation of red-mud-modified sludge-based biochar and its phosphorus adsorption efficiency and mechanism[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(7): 179-190. doi: 10.13205/j.hjgc.202607018

Citation:

ZHANG Chao, XIONG Renjiu, CAI Meiqiang, DONG Chunying. Research on preparation of red-mud-modified sludge-based biochar and its phosphorus adsorption efficiency and mechanism[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(7): 179-190. doi: 10.13205/j.hjgc.202607018

Citation:

ZHANG Chao, XIONG Renjiu, CAI Meiqiang, DONG Chunying. Research on preparation of red-mud-modified sludge-based biochar and its phosphorus adsorption efficiency and mechanism[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(7): 179-190. doi: 10.13205/j.hjgc.202607018

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Research on preparation of red-mud-modified sludge-based biochar and its phosphorus adsorption efficiency and mechanism

doi: 10.13205/j.hjgc.202607018

1. School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310018, China;
2. Tongxiang Urban Sewage Treatment Co., Ltd., Jiaxing 314500, China

Received Date: 2025-07-03
Available Online: 2026-09-01

Abstract

Abstract

To address the dual challenges of phosphorus resource scarcity and eutrophication control， this study innovatively proposed a sustainable waste-treats-waste strategy by preparing red-mud-modified sludge-based biochar （RMSBC） through the co-pyrolysis of red mud and sewage sludge. By systematically optimizing the preparation conditions， the material achieved a maximum phosphorus adsorption capacity of 28.57 mg/g at 800 ℃ with a red mud-to-sludge mass ratio of 3∶1， representing a remarkable 350% enhancement on maximum adsorption capacity compared with unmodified biochar （SBC）. Comprehensive characterizations， including SEM， XRD， EDS， FT-IR， and XPS analyses， demonstrated that red mud modification effectively enlarged the pore size from 7.91 nm to 20.33 nm， reduced the material electronegativity， and increased the pH_pzc from 2.01 to 3.37. The adsorption process followed the pseudo-second-order kinetic and Langmuir isotherm models， with electrostatic attraction and surface precipitation identified as the dominant mechanisms. Molecular dynamics simulations further verified the crucial role of Fe₃O₄ in the adsorption process. The material retained 61% of its initial adsorption capacity after five regeneration cycles and achieved 83% phosphorus removal efficiency in real wastewater samples. This study successfully demonstrates the synergistic valorization of two industrial wastes： red mud serves as an iron oxide reservoir to provide active sites， while sewage-sludge-derived biochar acts as a porous support， offering an economically viable and efficient solution for phosphorus pollution control and resource recovery.
- red mud,
- phosphate,
- modified sludge-based biochar,
- adsorption,
- functioning mechanism

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References(46)

References

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