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<p>This study introduces a sustainable eggshell–magnetite (ESM) biocomposite synthesized from waste eggshells and magnetite (Fe<sub>3</sub>O<sub>4</sub>) nanoparticles for efficient removal of hexavalent chromium [Cr(VI)] from aqueous solutions. The optimized ESM 2:1 (wt%) formulation achieved rapid and nearly complete Cr(VI) removal (99.05%) within 15&#xa0;min at pH 3.0. Response Surface Methodology (RSM) confirmed pH and adsorbent dose as the most influential parameters, showing strong synergistic effects on adsorption capacity. Comprehensive material characterization revealed a self-activating mechanism during Cr(VI) uptake. XRD analysis demonstrated that the ESM composite retained the crystalline signatures of both calcite (CaCO<sub>3</sub>) and Fe<sub>3</sub>O<sub>4</sub> while exhibiting intensified calcite peaks and suppressed Fe<sub>3</sub>O<sub>4</sub> reflections. BET analysis showed a 2.7-fold surface area increase after adsorption, confirming the generation of new mesoporosity. FTIR spectra evidenced shifts in Fe–O and <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(CO_3^{2-}\)</EquationSource> </InlineEquation> bands, verifying active participation of both functional groups in Cr(VI) reduction and binding. In addition, the ESM maintained over 89% removal efficiency after three regeneration cycles with an estimated treatment cost of USD 11.23&#xa0;m<sup>−3</sup>, demonstrating a scalable, low-cost, and circular-economy solution for decentralized wastewater treatment.</p> Graphical abstract <p></p>

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Design and evaluation of magnetically recoverable eggshell-based nanocomposites with high surface area for efficient Cr(VI) removal from wastewater

  • 期刊论文

  • 发表日期：

    2025年12月23日

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  • Amira Damarany,
  • Mohamed Hashim,
  • Ali Abdelhamid,
  • Abdulmalik Altuwayjiri,
  • Abdullah Alzlfawi,
  • Ahmed Farghaly

摘要

This study introduces a sustainable eggshell–magnetite (ESM) biocomposite synthesized from waste eggshells and magnetite (Fe3O4) nanoparticles for efficient removal of hexavalent chromium [Cr(VI)] from aqueous solutions. The optimized ESM 2:1 (wt%) formulation achieved rapid and nearly complete Cr(VI) removal (99.05%) within 15 min at pH 3.0. Response Surface Methodology (RSM) confirmed pH and adsorbent dose as the most influential parameters, showing strong synergistic effects on adsorption capacity. Comprehensive material characterization revealed a self-activating mechanism during Cr(VI) uptake. XRD analysis demonstrated that the ESM composite retained the crystalline signatures of both calcite (CaCO3) and Fe3O4 while exhibiting intensified calcite peaks and suppressed Fe3O4 reflections. BET analysis showed a 2.7-fold surface area increase after adsorption, confirming the generation of new mesoporosity. FTIR spectra evidenced shifts in Fe–O and \(CO_3^{2-}\) bands, verifying active participation of both functional groups in Cr(VI) reduction and binding. In addition, the ESM maintained over 89% removal efficiency after three regeneration cycles with an estimated treatment cost of USD 11.23 m−3, demonstrating a scalable, low-cost, and circular-economy solution for decentralized wastewater treatment.

Graphical abstract