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<p>Anthropogenic freshwater salinization is a growing global concern, often accompanied by heavy metal contamination from saline discharges such as industrial effluents and brines. Nanoscale zerovalent iron (nZVI) and its carboxymethylcellulose-functionalized form (CMC-nZVI) are widely proposed for redox-based heavy metal remediation. However, the post-sequestration stability of immobilized metals, particularly under saline conditions, remains poorly understood. This poses critical risks to long-term treatment efficacy and environmental fate. This study systematically examines both the initial sequestration and post-sequestration stability of the heavy metal Cu<sup>2</sup>⁺ by bare and CMC-nZVI across a wide salinity range (0.1–1 M NaCl) and in a representative saline wastewater matrix containing co-ions (Ca<sup>2</sup>⁺, Mg<sup>2</sup>⁺, SO<sub>4</sub><sup>2−</sup>). While &gt; 98% Cu<sup>2</sup>⁺ was reductively sequestered as Cu(I/II) oxides across all conditions within 5 min, salinity significantly destabilized copper sequestered by bare nZVI. Remobilization kinetics, modeled using Hill’s equation, revealed that increasing salinity from 0.1 to 1 M delayed the remobilization time (<i>t</i><sub>1/2</sub>) from 148 to 272 min. Conversely lowering nZVI dosages accelerated <i>t</i><sub>1/2</sub> (47–93 min) whereas lowering Cu<sup>2⁺</sup> loading influenced remobilization extent by suppressing it to 52–65% versus 78–86% at higher loading. Detailed characterization revealed that chloride-induced pitting facilitated oxidative dissolution of sequestered copper, while concurrent iron-oxide buildup modulated timing and extent of Cu<sup>2</sup>⁺ remobilization. In contrast, CMC coating on nZVI enhanced post-sequestration stability by suppressing pitting, limiting remobilization, and enabling re-capture of transiently released Cu<sup>2</sup>⁺, while preserving rapid initial sequestration. Background co-ions in the representative saline matrix moderately accelerated <i>t</i><sub>1/2</sub> and increased remobilization extent for bare nZVI, whereas CMC-nZVI maintained stable performance.</p> Graphical Abstract <p></p>

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Copper remediation from salinization-impacted water by iron nanoparticles: insights into post-sequestration remobilization and polymer-enhanced heavy metal stabilization

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • Sourjya Bhattacharjee,
  • Narmada C. Nair,
  • Sefeera Sadik,
  • Abdallah Shanableh

摘要

Anthropogenic freshwater salinization is a growing global concern, often accompanied by heavy metal contamination from saline discharges such as industrial effluents and brines. Nanoscale zerovalent iron (nZVI) and its carboxymethylcellulose-functionalized form (CMC-nZVI) are widely proposed for redox-based heavy metal remediation. However, the post-sequestration stability of immobilized metals, particularly under saline conditions, remains poorly understood. This poses critical risks to long-term treatment efficacy and environmental fate. This study systematically examines both the initial sequestration and post-sequestration stability of the heavy metal Cu2⁺ by bare and CMC-nZVI across a wide salinity range (0.1–1 M NaCl) and in a representative saline wastewater matrix containing co-ions (Ca2⁺, Mg2⁺, SO42−). While > 98% Cu2⁺ was reductively sequestered as Cu(I/II) oxides across all conditions within 5 min, salinity significantly destabilized copper sequestered by bare nZVI. Remobilization kinetics, modeled using Hill’s equation, revealed that increasing salinity from 0.1 to 1 M delayed the remobilization time (t1/2) from 148 to 272 min. Conversely lowering nZVI dosages accelerated t1/2 (47–93 min) whereas lowering Cu2⁺ loading influenced remobilization extent by suppressing it to 52–65% versus 78–86% at higher loading. Detailed characterization revealed that chloride-induced pitting facilitated oxidative dissolution of sequestered copper, while concurrent iron-oxide buildup modulated timing and extent of Cu2⁺ remobilization. In contrast, CMC coating on nZVI enhanced post-sequestration stability by suppressing pitting, limiting remobilization, and enabling re-capture of transiently released Cu2⁺, while preserving rapid initial sequestration. Background co-ions in the representative saline matrix moderately accelerated t1/2 and increased remobilization extent for bare nZVI, whereas CMC-nZVI maintained stable performance.

Graphical Abstract