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<p>Hexavalent chromium in river-fed irrigation systems remains a treatment concern because conventional reduction and precipitation processes require chemical inputs and are difficult to operate at decentralized sites. This study evaluated live <i>Azolla filiculoides</i> as a speciation-based polishing step for Cr(VI) in Euphrates River water. Filtered river water was adjusted to near-neutral pH, buffered with 10&#xa0;mM MES/HEPES, and spiked with 1–10&#xa0;mg L<sup>−1</sup> Cr(VI). Samples were incubated for 72&#xa0;h at near-ambient temperature with live biomass, heat-killed biomass, or no biomass. Performance was assessed using dissolved Cr(VI), total dissolved Cr, and a mass balance-derived detoxifying conversion efficiency (DCE%), which relates Cr(VI) disappearance to the net loss of dissolved total chromium. <i>A. filiculoides</i> outperformed all control treatments. Total dissolved Cr removal of 50.25–68.37% and dissolved Cr(VI) removal of 77.05–89.95% were recorded in the 1–10&#xa0;mg L<sup>−1</sup> range after 72&#xa0;h. DCE% ranged from 131.39 to 154.89%, indicating Cr(VI) detoxification beyond aqueous Cr loss. Cr(VI) removal was fastest during the first 24&#xa0;h. In pH-controlled assays at 5&#xa0;mg L<sup>−1</sup> initial Cr(VI), removal was highest at pH 6.5, with about 86% Cr(VI) removal and about 63% total dissolved Cr removal, whereas DCE% peaked at pH 5.5 at about 143%. Under the tested conditions, live <i>A. filiculoides</i> functioned as a low-input polishing step for moderately chromium-impacted river or canal water.</p> Graphical Abstract <p></p>

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Chromium phytoremediation by Azolla filiculoides from Euphrates water: nonlinear kinetics, isotherms, and redox-specific performance

  • 期刊论文

  • 发表日期：

    2026年5月24日

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  • O. M. Hasan,
  • Y. M. Yousif

摘要

Hexavalent chromium in river-fed irrigation systems remains a treatment concern because conventional reduction and precipitation processes require chemical inputs and are difficult to operate at decentralized sites. This study evaluated live Azolla filiculoides as a speciation-based polishing step for Cr(VI) in Euphrates River water. Filtered river water was adjusted to near-neutral pH, buffered with 10 mM MES/HEPES, and spiked with 1–10 mg L−1 Cr(VI). Samples were incubated for 72 h at near-ambient temperature with live biomass, heat-killed biomass, or no biomass. Performance was assessed using dissolved Cr(VI), total dissolved Cr, and a mass balance-derived detoxifying conversion efficiency (DCE%), which relates Cr(VI) disappearance to the net loss of dissolved total chromium. A. filiculoides outperformed all control treatments. Total dissolved Cr removal of 50.25–68.37% and dissolved Cr(VI) removal of 77.05–89.95% were recorded in the 1–10 mg L−1 range after 72 h. DCE% ranged from 131.39 to 154.89%, indicating Cr(VI) detoxification beyond aqueous Cr loss. Cr(VI) removal was fastest during the first 24 h. In pH-controlled assays at 5 mg L−1 initial Cr(VI), removal was highest at pH 6.5, with about 86% Cr(VI) removal and about 63% total dissolved Cr removal, whereas DCE% peaked at pH 5.5 at about 143%. Under the tested conditions, live A. filiculoides functioned as a low-input polishing step for moderately chromium-impacted river or canal water.

Graphical Abstract