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<p>Lignin-derived magnetic spheres were synthesized via an in-situ solvothermal route to obtain Fe₃O₄/lignin (LS–Fe₃O₄) composites, followed by amine functionalization using two widely reported strategies: (i) polyethyleneimine (PEI) coating/crosslinking and (ii) chitosan (CS) coating/crosslinking. Structural and surface characterizations confirmed successful magnetization and formation of amine-rich shells. Elemental analysis showed increased nitrogen contents after functionalization (<i>N</i> = 6.1 wt% for LS–Fe₃O₄–PEI and 4.8 wt% for LS–Fe₃O₄–CS), accompanied by a pronounced surface charge shift, with pHPZC increasing to ~ 9.24 for LS–Fe₃O₄–PEI. Under single-solute isotherm conditions (C₀ = 10–200&#xa0;mg L⁻¹, pH 6.0, 298&#xa0;K), LS–Fe₃O₄–PEI delivered high experimental adsorption capacities at Cₑ ≈ 200&#xa0;mg L⁻¹ (qₑ ≈ 223, 135, 87, and 170&#xa0;mg g⁻¹ for Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺, respectively), consistently outperforming LS–Fe₃O₄–CS and the non-aminated controls. Importantly, the amine-functionalized composites maintained strong performance under a stringent four-metal competitive system (Pb²⁺/Cd²⁺/Ni²⁺/Cu²⁺) and exhibited only moderate suppression in the presence of background electrolytes (1–10 mM) and humic substances (up to 10&#xa0;mg L⁻¹), indicating good matrix tolerance. Regeneration tests demonstrated stable reusability over multiple adsorption–desorption cycles with ultralow Fe and N leaching, supporting operational durability and safety. Practical applicability was further verified in real-water matrices, achieving ~ 95.8% Pb removal in tap water at 1&#xa0;mg L⁻¹. Overall, amine-functionalized Fe₃O₄/lignin spheres, particularly via the PEI route, provide a sustainable, magnetically recoverable platform for competitive heavy-metal removal.</p> Graphic abstract <p></p>

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Amine-functionalized Fe₃O₄/lignin composites for competitive removal of heavy metal ions

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Thi Thao Minh,
  • Dinh Nhi Bui

摘要

Lignin-derived magnetic spheres were synthesized via an in-situ solvothermal route to obtain Fe₃O₄/lignin (LS–Fe₃O₄) composites, followed by amine functionalization using two widely reported strategies: (i) polyethyleneimine (PEI) coating/crosslinking and (ii) chitosan (CS) coating/crosslinking. Structural and surface characterizations confirmed successful magnetization and formation of amine-rich shells. Elemental analysis showed increased nitrogen contents after functionalization (N = 6.1 wt% for LS–Fe₃O₄–PEI and 4.8 wt% for LS–Fe₃O₄–CS), accompanied by a pronounced surface charge shift, with pHPZC increasing to ~ 9.24 for LS–Fe₃O₄–PEI. Under single-solute isotherm conditions (C₀ = 10–200 mg L⁻¹, pH 6.0, 298 K), LS–Fe₃O₄–PEI delivered high experimental adsorption capacities at Cₑ ≈ 200 mg L⁻¹ (qₑ ≈ 223, 135, 87, and 170 mg g⁻¹ for Pb²⁺, Cd²⁺, Ni²⁺, and Cu²⁺, respectively), consistently outperforming LS–Fe₃O₄–CS and the non-aminated controls. Importantly, the amine-functionalized composites maintained strong performance under a stringent four-metal competitive system (Pb²⁺/Cd²⁺/Ni²⁺/Cu²⁺) and exhibited only moderate suppression in the presence of background electrolytes (1–10 mM) and humic substances (up to 10 mg L⁻¹), indicating good matrix tolerance. Regeneration tests demonstrated stable reusability over multiple adsorption–desorption cycles with ultralow Fe and N leaching, supporting operational durability and safety. Practical applicability was further verified in real-water matrices, achieving ~ 95.8% Pb removal in tap water at 1 mg L⁻¹. Overall, amine-functionalized Fe₃O₄/lignin spheres, particularly via the PEI route, provide a sustainable, magnetically recoverable platform for competitive heavy-metal removal.

Graphic abstract