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<p>Arsenic (As) contamination of groundwater is a serious global issue requiring effective and sustainable remediation strategies. For long-term As immobilization, this study explores the potential of in-situ magnetite precipitation, induced by anaerobic nitrate-reducing Fe(II) -oxidizing (NRFO) bacteria. A nitrate-intercalated layered double hydroxide (NO<sub>3</sub>-MgFe LDH) was introduced to provide nitrate as an electron acceptor for Fe(II) bio-oxidation and serve as an iron-based precursor in magnetite formation. The experimental results showed that NO<sub>3</sub>-MgFe LDH was transformed into green rust (GR) in the presence of Fe(II) and HCO<sub>3</sub><sup>−</sup>. Meanwhile, 0.5 g/L of NO<sub>3</sub>-MgFe LDH released cumulatively about 1.21 mM of nitrate within 12 h, promoting the transformation of GR into magnetite induced by <i>Acidovorax</i> sp. BoFeN1. As a result, the aqueous As concentration decreased from 2 mg/L to &lt;0.008 mg/L, with approximately 70% of As confined in recalcitrant Fe oxides, suggesting high potential for long-term As immobilization. Environmental factors influenced the transformation process: a lower Fe(II) concentration (0.5 mM) delayed GR formation, while varying HCO<sub>3</sub><sup>−</sup> concentrations (2.5–10 mM) had minimal effect. Subsequently, an elevated As level (5 mg/L) inhibited the bio-formation of magnetite, leading to lepidocrocite as the dominant mineral phase. Given the stability of magnetite, this study provides a cost-effective and environmentally friendly strategy for the durable in-situ remediation of As-contaminated groundwater.</p>

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Enhancing long-term As immobilization by NO3-MgFe LDH coupling with Acidovorax sp. BoFeN1

  • 期刊论文

  • 发表日期：

    2025年5月23日

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  • Qian-wen Liu,
  • Si-ya Liu,
  • Ying Fang,
  • Hui-qian Dai,
  • Zhi-an Wang,
  • Hai-pu Li

摘要

Arsenic (As) contamination of groundwater is a serious global issue requiring effective and sustainable remediation strategies. For long-term As immobilization, this study explores the potential of in-situ magnetite precipitation, induced by anaerobic nitrate-reducing Fe(II) -oxidizing (NRFO) bacteria. A nitrate-intercalated layered double hydroxide (NO3-MgFe LDH) was introduced to provide nitrate as an electron acceptor for Fe(II) bio-oxidation and serve as an iron-based precursor in magnetite formation. The experimental results showed that NO3-MgFe LDH was transformed into green rust (GR) in the presence of Fe(II) and HCO3−. Meanwhile, 0.5 g/L of NO3-MgFe LDH released cumulatively about 1.21 mM of nitrate within 12 h, promoting the transformation of GR into magnetite induced by Acidovorax sp. BoFeN1. As a result, the aqueous As concentration decreased from 2 mg/L to <0.008 mg/L, with approximately 70% of As confined in recalcitrant Fe oxides, suggesting high potential for long-term As immobilization. Environmental factors influenced the transformation process: a lower Fe(II) concentration (0.5 mM) delayed GR formation, while varying HCO3− concentrations (2.5–10 mM) had minimal effect. Subsequently, an elevated As level (5 mg/L) inhibited the bio-formation of magnetite, leading to lepidocrocite as the dominant mineral phase. Given the stability of magnetite, this study provides a cost-effective and environmentally friendly strategy for the durable in-situ remediation of As-contaminated groundwater.