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<p>Selenium (Se) contamination, particularly as selenate [Se(VI)], is more problematic than Se(IV) and other Se species due to its high solubility, mobility and bioavailability, which contribute to long-range environmental contamination. Its acute toxicity at trace levels also poses risks to water quality and remains a global concern. No universally effective or sustainable remediation method exists for Se(VI) at trace concentrations in environmental waters. Batch adsorption tests were performed on three carbon-based sorbents: sewage-based activated carbon (SBAC), commercial activated carbon (CAC) and biochar derived from spruce, pine and fir wood (SPF BC). Removal efficiencies followed the order of SBAC &gt;  &gt; SPF BC &gt; CAC, achieving approximately 85%, 18% and 2% removal, respectively, at 400&#xa0;µg L<sup>−1</sup> Se(VI). SBAC was further investigated for the effects of adsorbent dosage, contact time, temperature, sequential adsorption and competing anions. SBAC exhibited rapid adsorption kinetics, reaching near-equilibrium within 0.5&#xa0;h and achieving a maximum capacity of 10,297&#xa0;μg&#xa0;g<sup>−1</sup>, consistent with Langmuir model and indicative of monolayer adsorption. Se(VI) uptake was largely independent of temperature (7 °C–35 °C). Although elevated SO<sub>4</sub><sup>2−</sup> and Cl⁻ inhibited adsorption, SBAC retained substantial Se(VI) removal, indicating selective binding. Sequential adsorption successfully reduced Se(VI) concentrations below the 5&#xa0;μg L<sup>−1</sup> regulatory threshold. Spectroscopic analysis revealed that Se(VI) removal primarily occurred through electrostatic attraction and surface complexation involving hydrogen bonding and dipole–dipole interactions with oxygen-containing functional groups. This work demonstrates that SBAC generated from municipal waste within a circular-resource framework can remove low Se(VI) concentrations to regulatory levels under environmentally relevant conditions, with pilot-scale testing recommended for large-scale application.</p>

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Sewage-sludge-based activated carbon as a circular adsorbent for efficient selenate removal from water

  • 期刊论文

  • 发表日期：

    2026年4月17日

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  • N. R. Nicomel,
  • L. Y. Li

摘要

Selenium (Se) contamination, particularly as selenate [Se(VI)], is more problematic than Se(IV) and other Se species due to its high solubility, mobility and bioavailability, which contribute to long-range environmental contamination. Its acute toxicity at trace levels also poses risks to water quality and remains a global concern. No universally effective or sustainable remediation method exists for Se(VI) at trace concentrations in environmental waters. Batch adsorption tests were performed on three carbon-based sorbents: sewage-based activated carbon (SBAC), commercial activated carbon (CAC) and biochar derived from spruce, pine and fir wood (SPF BC). Removal efficiencies followed the order of SBAC >  > SPF BC > CAC, achieving approximately 85%, 18% and 2% removal, respectively, at 400 µg L−1 Se(VI). SBAC was further investigated for the effects of adsorbent dosage, contact time, temperature, sequential adsorption and competing anions. SBAC exhibited rapid adsorption kinetics, reaching near-equilibrium within 0.5 h and achieving a maximum capacity of 10,297 μg g−1, consistent with Langmuir model and indicative of monolayer adsorption. Se(VI) uptake was largely independent of temperature (7 °C–35 °C). Although elevated SO42− and Cl⁻ inhibited adsorption, SBAC retained substantial Se(VI) removal, indicating selective binding. Sequential adsorption successfully reduced Se(VI) concentrations below the 5 μg L−1 regulatory threshold. Spectroscopic analysis revealed that Se(VI) removal primarily occurred through electrostatic attraction and surface complexation involving hydrogen bonding and dipole–dipole interactions with oxygen-containing functional groups. This work demonstrates that SBAC generated from municipal waste within a circular-resource framework can remove low Se(VI) concentrations to regulatory levels under environmentally relevant conditions, with pilot-scale testing recommended for large-scale application.