ORIGINAL RESEARCH article
Front. Chem.
Sec. Analytical Chemistry
Mechanistic insights into pyrolysis 2 temperature-dependent lead (Pb) stabilization in 3 phytoremediation residue-derived biochar
Provisionally accepted
- 1Shenzhen Polytechnic, Shenzhen, China
- 2Shandong Agricultural University, Tai'an, China
- 3Technical Centre for Soil, Agriculture and Rural Ecology and Environment, Ministry of Ecology and Environment, Beijing, Beijing, China
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The substantial generation of hazardous, metal-enriched 16 biomass residues poses significant risks of secondary 17 contamination, presenting a critical bottleneck to the broader 18 implementation of phytoremediation that urgently requires 19 effective treatment solutions. This study addressed this 20 challenge by pyrolyzing Pb-enriched biomass (BMPb) across a 21 temperature range (300-700 °C) to produce Pb-enriched biochar 22 (BCPb), evaluating its efficacy for safe residue management. The 23 results demonstrated that pyrolysis effectively reduced the 24 volume of BMPb, and the produced BCPb significantly enriched 25 and immobilized Pb. Element analysis revealed distinct 26 stabilization mechanisms: Pb2(P4O12) and PbCO3 precipitation 27 dominated Pb immobilization at 400 °C, whereas Pb3(CO3)2(OH)2, 28 Pb2(P4O12), and NaAlSiO4 became predominant at temperatures 29 ≥500 °C. Sequential extraction of Pb (BCR) demonstrated a 30 consistent decline in the more labile Pb fractions (exchangeable, 31 F1, and reducible, F2) with increasing pyrolysis temperature, 32 concurrent with a significant increasing in the stable fractions 33 (oxidizable, F3, and residual, F4). Notably, the combined F1+F2 34 fraction decreased substantially (17% at 700 °C), while the stable 35 F3+F4 fraction increased correspondingly (83% at 700 °C), 36 indicating markedly reduced Pb bioavailability and ecological 37 risk at elevated temperatures. Leaching tests confirmed that Pb 38 release from all BCPb samples remained well below relevant 39 regulatory thresholds when the pH higher than 2 ( < 9.98mg·g-1 40 vs. 10.0 mg·g-1), with leaching susceptibility inversely related to 41 pyrolysis temperature. Soil simulation experiments further 42 indicated a conversion of bioavailable Pb (F1+F2) in 43 BCPb-amended systems towards stable forms (F3+F4), 44 confirming low ecological risk. Overall, these findings 45 suggested that pyrolysis of BMPb at temperatures above 500 °C 46 shows great promise as an effective and safe method for treating 47 phytoremediation residues, demonstrating high stability and 48 low ecological risk to both water and soil environments under 49 most natural conditions, though careful management is 50 required under extreme acidic scenarios.
Keywords: Phytoremediation residue, lead (Pb), Pyrolysistemperature, stabilization, Ecological risk
Received: 15 Sep 2025; Accepted: 27 Oct 2025.
Copyright: © 2025 Liu, Wang, Pang, Wang, Li and Wang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Tongtong Li, litongtong@tcare-mee.cn
Lei Wang, wangleicraes@163.com
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