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Purpose <p>Soil contamination by typical monoaromatic hydrocarbons such as benzene and toluene (BT) poses severe environmental and health risks, prompting the need for eco-friendly remediation strategies using biochar. Its abiotic removal efficacy for BT was systematically investigated here to identify the contributions of adsorption and chemical degradation, evaluate the impacts of various factors on adsorption efficacy, and clarify adsorption mechanisms.</p> Methods <p>Biochar was produced at pyrolysis temperatures of 400, 500, and 600&#xa0;°C. Controlled experiments in sterilized soil, with and without biochar amendment, were conducted to quantify its contribution to abiotic BT removal, together with adsorption and chemical degradation experiments. Adsorption isotherms were evaluated across different pyrolysis temperatures, biochar addition amounts (2–6% w/w), and equilibrium temperatures (15–35&#xa0;°C), alongside kinetic and desorption studies, to comprehensively investigate BT removal mechanisms in biochar-amended soils.</p> Results <p>The addition of 1% biochar enhanced abiotic removal of benzene and toluene by 33.8% and 38.8%, respectively, with adsorption identified as the dominant mechanism. Biochar exhibited a stronger affinity for benzene, attributed to its greater hydrophobicity and preferential interaction with hydrophobic surfaces. Optimal adsorption occurred under conditions of 500&#xa0;°C pyrolysis temperature, 4% biochar addition, and 25&#xa0;°C equilibrium temperature. Freundlich isotherm modeling and Gibbs free energy values confirmed a multilayer physisorption process driven by heterogeneous interactions, including hydrophobic site selectivity, π-π electron donor-acceptor bonding, and electrostatic forces, with minimal contributions from pore-filling or monolayer adsorption. Adsorption kinetics were best described by the pseudo-second-order model. Desorption experiments further demonstrated the effectiveness and stability of biochar (particularly 500&#xa0;°C) as an adsorbent.</p> Conclusion <p>This study bridges critical gaps by comparing variable-specific adsorption differences, validating biochar’s superiority over pure soil, and providing mechanistic insights into surface-driven physisorption, offering actionable guidelines for optimizing biochar-based remediation of volatile organic compounds (VOCs)-contaminated soils through parameter optimization aligned with contaminant properties and environmental conditions.</p> Graphical abstract <p></p>

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Enhanced abiotic removal of soil monoaromatic hydrocarbons by biochar addition

  • 期刊论文

  • 发表日期：

    2026年3月3日

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  • Huaiyu Ge,
  • Bing Hong,
  • Hao Zhang,
  • Tianyu Hu,
  • Jian Kang,
  • Yinuo Wang,
  • Jingyi Wang,
  • Xiaoya Zheng,
  • Hua Fang,
  • Shutan Ma,
  • Juan Zhao,
  • Ting Wu

摘要

Purpose

Soil contamination by typical monoaromatic hydrocarbons such as benzene and toluene (BT) poses severe environmental and health risks, prompting the need for eco-friendly remediation strategies using biochar. Its abiotic removal efficacy for BT was systematically investigated here to identify the contributions of adsorption and chemical degradation, evaluate the impacts of various factors on adsorption efficacy, and clarify adsorption mechanisms.

Methods

Biochar was produced at pyrolysis temperatures of 400, 500, and 600 °C. Controlled experiments in sterilized soil, with and without biochar amendment, were conducted to quantify its contribution to abiotic BT removal, together with adsorption and chemical degradation experiments. Adsorption isotherms were evaluated across different pyrolysis temperatures, biochar addition amounts (2–6% w/w), and equilibrium temperatures (15–35 °C), alongside kinetic and desorption studies, to comprehensively investigate BT removal mechanisms in biochar-amended soils.

Results

The addition of 1% biochar enhanced abiotic removal of benzene and toluene by 33.8% and 38.8%, respectively, with adsorption identified as the dominant mechanism. Biochar exhibited a stronger affinity for benzene, attributed to its greater hydrophobicity and preferential interaction with hydrophobic surfaces. Optimal adsorption occurred under conditions of 500 °C pyrolysis temperature, 4% biochar addition, and 25 °C equilibrium temperature. Freundlich isotherm modeling and Gibbs free energy values confirmed a multilayer physisorption process driven by heterogeneous interactions, including hydrophobic site selectivity, π-π electron donor-acceptor bonding, and electrostatic forces, with minimal contributions from pore-filling or monolayer adsorption. Adsorption kinetics were best described by the pseudo-second-order model. Desorption experiments further demonstrated the effectiveness and stability of biochar (particularly 500 °C) as an adsorbent.

Conclusion

This study bridges critical gaps by comparing variable-specific adsorption differences, validating biochar’s superiority over pure soil, and providing mechanistic insights into surface-driven physisorption, offering actionable guidelines for optimizing biochar-based remediation of volatile organic compounds (VOCs)-contaminated soils through parameter optimization aligned with contaminant properties and environmental conditions.

Graphical abstract