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Pyrolysis temperature governs the immobilization mechanisms and selectivity of medulla stachyuri-derived biochar for heavy metals
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DOI：10.1007/s10653-026-02992-5.png)
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Abstract
En 中文
The development of efficient and sustainable adsorbents is crucial for remediation heavy metal contamination in both aqueous and terrestrial environments. Biomass-derived biochar shows great promise, yet its adsorption performance is highly dependent on both the feedstock properties and the pyrolysis temperature. However, a systematic understanding of how temperature dictates the adsorption mechanisms, especially for multi-metal systems, remains limited for novel biomass precursors. Therefore, the stem pith of Medulla stachyuri (MS) was utilized to prepare biochars at different pyrolysis temperatures (400, 600, and 800 °C, denoted as MBCs) and to investigate their adsorption behavior for Pb2+ and Cu2+. The results indicated that higher pyrolysis temperatures significantly enhanced the specific surface area (reaching 322.94 m2/g for MBC-800) and ash content but decreased the oxygen-containing functional groups. MBC-800 exhibited superior adsorption capacities for Pb2+ (2139.25 mg/g) and Cu2+ (970.68 mg/g), with remarkable selectivity for Pb2+ in binary systems. Mechanistic studies revealed that the dominant adsorption mechanism shifted from surface complexation at lower temperatures to precipitation induced by the biochar's inherent inorganic components (e.g., SO₄2⁻ forming PbSO₄) at higher temperatures. Component contribution analysis quantitatively confirmed that the water-soluble fraction in MBC-800 was responsible for over 78% of Pb2+ immobilization. Furthermore, MBC-800 demonstrated excellent stability with the lowest desorption rate, indicating a low risk of secondary pollution. This work highlights the superiority of high-temperature biochar from MS for efficient and stable heavy metal removal, providing new insights into the precipitation-dominated mechanism and the high-value utilization of medicinal plant residues.
Keywords:
Biomass
Lead
Copper
Adsorption
Sorption
Desorption
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4.6K
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